international seminar on current ... - physics.puchd.ac.in
TRANSCRIPT
International Seminar on Current Trends in
Quantum Gases, BEC and Solitons
3–6 March 2014
Department of Physics
Panjab University
Chandigarh
Supported by: DST TPSC-ARW; INSA; BRNS; Avra Labs;
UGC Unassigned Grant and Panjab University
Department of Physics, Panjab University, Chandigarh is organizing
INTERNATIONAL SEMINAR ON CURRENT TRENDS IN QUANTUM GASES, BEC
AND SOLITONS (3 - 6 March 2014)
You are cordially invited to the
Inauguration Programme on Monday, March 3, 2014 at 10.00 AM
at the
Main Auditorium, Dept. of Physics, Panjab University, Chandigarh
Prof. T. V. Ramakrishnan DAE Homi Bhabha Professor of Physics, Benaras Hindu University, Varanasi Distinguished Associate, Centre for Condensed Matter Theory, IISc Bangalore
has kindly consented to inaugurate the programme
and
Prof. Arun K Grover, Vice - Chancellor
Panjab University, Chandigarh shall preside over the function
Dr. C.N. Kumar Prof. V.P. Singh Secretary QGBECS 2014 Chairman
Kindly stay for cup of Tea at 11.15 A.M.
ADVISORY COMMITTEE
• Prof. A.K. Grover (V-C, PU, Chandigarh) • Prof. K.N. Pathak (PU, Chandigarh) • Prof. J. Bosse (Freie Univ., Berlin) • Prof. A. Pelster (Kaiserslautern Univ., Berlin)
LOCAL ORGANISING COMMITTEE
• Prof. Manjit Kaur • Prof. V.K. Jindal • Prof. K. Dharamvir • Prof. N. Goyal • Dr. C.N. Kumar (Secretary) • Dr. Ranjan Kumar • Dr. S. Srivastava • Dr. Kuldeep Kumar • Dr. Bimal Rai
List of Speakers
Name Title of Talk
1. Prof. J. Bosse Freier Universität, Berlin
1)Hartree–Fock approximation for BEC revisited 2)Fluctuating ground–state occupation number for trapped BEC
2. Prof. M. Howard Lee The University of Georgia, Georgia Understanding Ergodicity From Chaos
3. Prof. Carlos Sa de Melo Georgia Institute of Technology, Georgia
"Who Is The Lord Of The Rings In The Zeeman-Spin-Orbit Saga: Majorana, Dirac Or Lifshitz?"
4. Prof. Herwig Ott Technische Universität Kaiserslautern, Germany
1) Bose-Einstein Condensation: An Experimental Overview 2) Dissipation Controlled Dynamics In Open Many-Body Quantum Systems
5. Prof. A. Pelster Technische Universität Kaiserslautern, Germany
1)Perturbative and Non-Perturbative Methods for Tackling the Dirty Boson Problem 2)Tuning the Quantum Phase Transition of Bosons in Optical Lattices
6. Dr. A. Banerjee Centre for Advanced Technology, Indore
Density Functional Theory of dipolar fermions: Assessment of exchange and correlation energies
7. Dr. A. Bhattacherjee University of
The Optomechanical Dicke Model As A New Tool To Measure Weak Force Delhi, Delhi
8. Prof. B. Dey University of Pune, Pune
Pinning of Hidden Vortices in Bose-Einstein Condensate
9. Dr. P. Muruganandam Bharathidasan
Properties Of Dipolar Bose-Einstein Condensates From Numerical Solutions of Gross-Pitaevskii Equation
University, Tiruchirappalli
10 Prof. T.V. Ramakrishnan Inaugural Talk Banaras Hindu University, Varanasi 11 Prof. G.S. Singh Thermodynamics of Trapped Atomic Quantum
Gases with Synthetic Spin-Orbit Coupling IIT Roorkee, Roorkee 12 Dr. Utpal Roy
IIT Patna TBA
13 Dr Rishi Sharma TIFR Mumbai
Validating Simple Dynamical Simulations of the Unitary Fermi Gas
Seminars by Participants
1 Ravichandaran.R Nonlinear Dynamics of Blood Pressure Waves In Large Elastic Tubes
2 E. Parasuraman Excitations of Localized Modes Via Modulational Instability In Carbon Nanotubes (CNT) with Present wnd Absent ff Electron-Phonon Interaction
3 K. Sakkaravarthi Painleve Integrability Analysis And Soliton Solution of Multicomponent Yajima-Oikawa System
4 Arvind Sharma Optical Pulse Propagation At Discrete Thin-Film Waveguide Structure
5 Swarniv Chandra Electron Acoustic Solitary Wavestructures In Quantum Plasmas At Finite Temperature Containing Two Kind Ofelectrons.
6 Rashi Sachdeva Effect Of Artificial Gauge Field On Supersolid Phase In Ultracold Atomic Condensates
7 Bindiya Arora Van Der Waals Coefficients For The Alkali-Metal Atoms In The Material Mediums
8 Renu Bala Weakly interacting trapped quantum gases
Poster presentations
1 Reena Gupta Thermodynamical Study of Two-Dimensional Spin-Orbit-Coupled Bose Gas
2 Priyanka Optomechanical Effects on Self-Organization of A BEC In An Superfluid Properties of BECs In Optical Lattice
3 Rama Gupta, Amit Goyal Rogue waves in BEC Systems 4 Sonam Mahajan Ground State Cooling Of Mechanical Oscillator
Using A Bose-Einstein Condensate With Back-Action Cooling And Cold-Damping Feedback Schemes
5 Neha Aggarwal Steady State Analysis And Photodetection Measurements For The Optomechanical Dicke Model
PARTICIPANT LIST
1 Ajay Nath IIT, Patna [email protected]
2 Anjan Giri IIT Hyderabad [email protected]
3 S.Sabari PU, Puducherry [email protected]
4 Ravichandaran.R Per. Uni. ,Selam [email protected]
5 E. Parasuraman Per. Uni., Selam [email protected]
6 Siddharth Acharya HPU, Shimla [email protected]
7 K. Sakkaravarthi BDU, Tiruchirapalli [email protected]
8 C. Gandhi VIT, Vellore [email protected]
9 Arvind Sharma GDC, Bikaner [email protected]
10 Swarniv Chandra Jadavpur Uni.,Kolkata [email protected]
11 Soumendu Jena Thapar Uni.,Patiala [email protected]
12 Lalit K. Saini SVNIT,Surat [email protected]
13 Sukla Pal SNBNCBS, Kolkata [email protected]
14 Sonam Mahajan DU, Delhi [email protected]
15 Reena Gupta IIT, Roorkee [email protected]
16 Rashi Sachdeva IIT, Kanpur [email protected]
17 Arpit Dua IIT, Roorkee [email protected]
18 Neha Aggarwal DU,Delhi [email protected]
19 Priyanka MNCSC,Delhi [email protected]
20 Reshma P SNPC, Kerala [email protected]
21 Paramjit Kaur IIT, Roorkee [email protected] 22 Nawel Djouhri Algeria [email protected]
23 Komal Kumari HPU,Shimla [email protected]
24 Bindiya Arora GNDU, Amritsar [email protected]
25 Saroj Sharma Amity U [email protected]
26 Priya Arora KUK, Kurukshetra [email protected]
27 Niranjan M RRI, Bangalore [email protected]
28 Rama Gupta PU, Chandigarh [email protected]
29 Renu Bala PU, Chandigarh [email protected]
30 Amit Goyal PU, Chandigarh [email protected]
31 V K Sharma PU, Chandigarh 32 Alka PU, Chandigarh 33 Kanchan K De PU, Chandigarh 34 J. S. Virdi PU, Chandigarh
Speakers Abstract BOSE-EINSTEIN CONDENSATION: AN EXPERIMENTAL OVERVIEW
Herwig Ott Department of Physics, University of Kaiserslautern, Germany E-mail: [email protected] Abstract: The advent of Bose-Einstein condensation in 1995 [1] marks the beginning of the rapidly growing research field of ultracold quantum gases. This development was accompagnied by new experimental techniques that allowed to study these fascinating quantum objects with ever increasing precision. Nowadays, the field has spread in a variety of sub-fields, each having a dedicated portfolio of preparation and detection methods. This talk gives an overview of the various developments in the field with special emphasis on the experimental achievements.
References
[1] Anderson et al. Science(269), 198 (1995).
DISSIPATION CONTROLLED DYNAMICS IN OPEN MANY-BODY QUANTUM SYSTEMS Herwig Ott Department of Physics, University of Kaiserslautern, Germany E-mail: [email protected]
Abstract: Ultracold quantum gases are usually well isolated from the environment. This allows to study the ground state properties and the unitary dynamics of a many-body quantum system under almost ideal conditions. Introducing a controlled coupling to the environment “opens” the quantum system and non-unitary dynamics can be investigated. Such an approach provides new opportunities to study fundamental quantum effects and to engineer robust many-body quantum states.
In this talk I will present an experimental platform [1,2,3] that allows for the controlled engineering of dissipation in ultracold quantum gases by means of localized particle losses. Changing the strength of the couplingto the environment (loss rate) induces quantum Zeno dynamics where we can studygeneric signatures of open quantum systems [4] and non-equilibrium quantum dynamics.
References
[1] T. Gericke et al., Nature Physics 4, 949 (2008). [2] P. Würtz et al., Phys. Rev. Lett. 103, 080404 (2009). [3] V. Guarrera et al., Phys. Rev. Lett. 107, 160403 (2011). [4] G. Barontini et al., Phys. Rev. Lett. 110, 035302 (2013).
UNDERSTANDING ERGODICITY FROM CHAOS M Howard Lee Department of Physics, University of Georgia, Athens, Georgia, USA
Abstract: For many years now ergodicity has been studied as a mathematical issue, steeped in abstract mathematical concepts. Recently I have given a physical theory for ergodicity based on physical properties like linear response and other many-body dynamics. These developments raise questions on the existence of ergodicity in an ordered state such as a BEC state. Recent studies on chaos provide why a system must be chaotic to be ergodic. But the converse may not hold. The talk will be more of an overview rather than a series of proofs.
"Who is the Lord of the Rings in the Zeeman-spin-orbit Saga: Majorana, Dirac or Lifshitz?"
Carlos A. R. Sa de Melo Georgia Institute of Technology, USA
Abstract: I discuss the simultaneous effects of Zeeman and spin-orbit fields during the evolution from BCS to BEC superfluidity for ultra-cold fermions. I focus on spin-orbit couplings with equal Rashba and Dresselhaus strengths, and show that topological phase transitions of the Lifshitz class occur through the emergence of Majorana and/or Dirac fermions as Zeeman and spin-orbit fields are varied. Topological quantum phase transitions in superfluids with non-s-wave order parameters have been conjectured theoretically for p-wave and d-wave systems for many years, but never observed experimentally due to the absence of tunable parameters. However, Zeeman or spin-orbit fields and interactions can be tuned in the context of ultra-cold atoms and allow for the visitation of several different phases. For systems with zero Zeeman field, the evolution from BCS to BEC superfluidity in the presence of spin-orbit effects is only a crossover [1] as the system remains fully gapped, even though a triplet component of the order parameter emerges. In contrast, for finite Zeeman fields, spin-orbit coupling induces a triplet component in the order parameter that produces nodes in the quasiparticle excitation spectrum leading to bulk topological phase transitions of the Lifshitz type [2]. Additionally, a fully gapped phase exists, where a crossover from indirect to direct gap occurs. For spin-orbit couplings with equal Rashba and Dresselhaus strengths the nodal quasi-particles are Dirac fermions that live at and in the vicinity of rings of nodes. Transitions from and to nodal phases can occur via the emergence of zero-mode Majorana fermions at phase boundaries, where rings of nodes of Dirac fermions annihilate [3]. Lastly, I characterize different phases via spectroscopic and thermodynamic properties and conclude that Lifshitz is the “Lord of the Rings”.
References
[1] Li Han, C. A. R. Sá de Melo, “Evolution from BCS to BEC superfluidity in the presence of spin-orbit coupling”, Physical Review A 85, 011606(R) (2012), see also arXiv:1106.3613v1.
[2] Kangjun Seo, Li Han and C. A. R. Sá de Melo, “Topological phase transitions in ultra-cold Fermi superfluids: the evolution from BCS to BEC under artificial spin-orbit fields”, Physical Review A 85, 033601 (2012), see also arXiv:1108.4068v2.
[3] Kangjun Seo, Li Han and C. A. R. Sá de Melo, “Artificial spin-orbit coupling in ultra-cold Fermi superfluids”, arXiv:1110.6364v1.
[4] Kangjun Seo, Li Han, and C. A. R. Sá de Melo, “Emergence of Majorana and Dirac Particles in Ultracold Fermions via Tunable Interactions, Spin-Orbit Effects, and Zeeman Fields”, Physical Review Letters 109, 105303 (2012), see also arXiv:1201.0177v1.
SPIN-ORBIT COUPLED FERMI GASES I: INTRODUCTION AND FEW-BODY PHYSICS Wei Zhang Department of Physics, Beijing, China Abstract: The realization of synthetic spin-orbit coupling (SOC) adds another important piece to the already versatile toolbox of controllability in cold atoms. In this talk, I will first introduce some basics on synthetic gauge field and spin-orbit coupling in cold atomic gases, and then discuss the two-body scattering problem and two-body bound state within such a system. Specifically, We derive the modified Bethe-Peierls boundary condition for the systems with SOC, and obtain the analytical expression of the low-energy inter-atomic scattering amplitude, as well as the algebra equation for the two-atom bound-state energy in both three and quasi-low dimensional confinements. With our result we examine the validity of the effective contact interaction for the spin-orbit coupled atomic gases.
SPIN-ORBIT COUPLED FERMI GASES II: EXOTIC PAIRING STATES IN 2D GASES Wei Zhang Department of Physics, Beijing, China Abstract: Theoretical investigation has demonstrated that the interplay of SOC, pairing superfluidity and effective Zeeman fields can lead to exotic superfluid phases in various dimensions. In these systems, as SOC mixes different spin states, both intra- and inter-branch pairings can take place and the competition between them results in rich phase structures. In this talk, I will investigate the pairing physics in a two-dimensional Fermi gas with Rashba SOC. In th presence of an out-of-plane Zeeman field, a topological superfluid (TSF) state will be stabilized in a large parameter region on the phase diagram by tuning through the Feshbach resonance. The TSF state acquires a chiral Majorana edge mode protected by the gap in the bulk, and can be understood in the weak-coupling limit as a consequence of intra-branch pairing when the chemical potential lies within or below the gap opened by the out-of-plane Zeeman field. As both the inversion and the time-reversal symmetries are broken in the system, the TSF state belongs to class D. The TSF state will evolve into a topological Fulde-Ferrell (FF) state if an additional in-plane Zeeman field is applied Similar to the case of a TSF state, in the weak-coupling limit, the emergence of the topological FF state can be understood as a result of single-branch pairing within the lower helicity branch. The resulting pairing state would preserve all topological properties provided that the deformation of the Fermi surface should not be drastic enough to violate the single-branch pairing scenario
Properties of Dipolar Bose-Einstein Condensates from Numerical Solutions of Gross-Pitaevskii Equation
Paulsamy Muruganandam Department of Physics, Bharathidasan University,Tiruchirappalli 620024, TN, India Abstract: Many of the static and dynamic properties of an atomic Bose-Einstein condensate (BEC) are usually studied by solving the mean-field Gross-Pitaevskii (GP) equa tion, which is a nonlinear partial differential equation for short-range atomic interaction. BEC of atoms with long-range dipolar atomic interaction are used in theoretical and experimental studies. For dipolar atomic interaction, the GP equation involves nonlocal nonlinear term to account the dipole-dipole interaction. We propose a time iterative split-step method for the solution of the time-dependent Gross-Pitaevskii equation, where all nonlinear and linear nonderivative terms are treated separately from the time propagation with the kinetic energy terms. In the case of dipolar GP equation and the dipolar interaction term is evaluated using Fourier transform. We discuss the static and dynamic properties of trapped both conventional and dipolar BECs using the numerical solution of the GP equation. References [1] P. Muruganandam and S. K. Adhikari, Fortran programs for the time-dependent Gross-Pitaevskii equation in a fully anisotropic trap, Comp. Phys. Commun. 180, 1888-1912 (2009). [2] P. Muruganandam and S. K. Adhikari, Numerical and variational solutions of the dipolar Gross-Pitaevskii equation in reduced dimensions, Laser Phys. 22, 813-820 (2012).
Thermodynamics of Trapped Atomic Quantum Gases with Synthetic Spin-Orbit Coupling G. S. Singh Physics Department, Indian Institute of Technology Roorkee, Roorkee Abstract: The study of ultracold atoms and matter waves has been at the forefront to mimic many physical phenomena ever since the Bose-Einstein condensation (BEC) was realized in alkali vapors in 1995. Enhanced pace to this interest generated by theoretical proposals to create non-Abelian gauge fields which could lead to synthetic spin-orbit coupling (SOC) has further intensified after recent success in achieving experimentally such a coupling in both bosonic and fermionic systems. The concept of engineered SOC together with salient features of theoretically studied various SO-coupled systems and their probable applications are reviewed. A general expression for density of states (DOS) of d-dimensional ideal quantum gases under combined influence of power-law trapping and isotropic spin orbit coupling is derived. The expression for the grand potential and hence for several thermodynamic quantities are shown to be amenable to exact analytical forms which are simple if d is an odd integer. A remarkable condition, < 2d with as the power-law exponent, governs the appearance of BEC in such a case. The harmonically trapped 3D gases with isotropic SOC are then considered specifically. It is established through analytical and numerical studies of thermodynamic quantities that the Weyl SO coupling induces interaction which weakens “effective” attraction (repulsion) of the exchange symmetry present in zero-coupling Bose (Fermi) gas. It is discussed that many interesting features of SO coupled systems can be understood in terms of coupling-induced modifications in statistical inter particle potential. The temperature dependence of some thermodynamic quantities for a uniform Bose gas is found to have signature of the incipient BEC in very weak coupling regime. The transition temperature is found to decrease with increase of coupling strength supporting the concept of the weakening of the statistical attractive interaction. It is pointed out that the fluctuation dissipation theorem could be utilized to verify appearance of anomalous behaviors of some thermodynamic quantities as soon as the Fermi level goes down the Dirac point on increasing the coupling strength in uniform fermions.
THE OPTOMECHANICAL DICKE MODEL AS A NEW TOOL TO MEASURE WEAK FORCE Neha Aggarwal, Sonam Mahajan, Aranya B Bhattacherjee and Man Mohan Department of Physics and Astrophysics, University of Delhi, Delhi-110007, India Abstract: We present a detailed study to analyse the Dicke quantum phase transition within the thermodynamic limit for an optomechanically driven Bose-Einstein condensates in a cavity. The photodetection-based quantum optical measurements have been performed to study the dynamics and excitations of this optomechanical Dicke system. For this, we discuss the fluorescence spectrum and the homodyne spectrum of the system. We have observed that both the spectra exhibit distinct features that can be identified with the photonic, atomic and phononic branches. In the fluorescence spectra, we further observe an asymmetric coherent energy exchange between the three degrees of freedom of the system in the superradiant phase arising as a result of optomechanical interaction and Bloch-Siegert shift. In the semi-classical steady state analysis, an additional external mechanical pump is also shown which modifies the critical value of atom-photon coupling needed to observe the quantum phase transition. Such system can be used as a new quantum device to measure weak forces. We further show how the mechanical pump frequency and cavity-laser detuning play a significant role in producing extremely cold condensates.
Density Functional Theory of dipolar fermions: Assessment of exchange and correlation energies Arup Banerjee1 and Amit K. Das2
1
Homi Bhabha National Institute, Mumbai, India
BARC Training School at RRCAT, Raja Ramanna Centre for Advanced Technology, Indore, India
2
Email :
Laser Material Processing Division, Raja Ramanna Centre for Advanced Technology, Indore
452013
Abstract: Recently considerable attention has been focused on the study of dipolar Fermi gas due
to its markedly different characteristic as compared to the archetypal Fermi gas composed of
electrons arising from the long-range and anisotropic inter-particle interaction. Theoretical
studies on various properties of the dipolar Fermi gas requires accurate determination of ground
state wave function or density of this system. Density functional theory (DFT) is a formalism
which takes the effect of both exchange and correlation between the fermions in an efficient
and accurate manner. In recent years DFT has become an indispensible tool for studying many-
electron systems like atoms, molecules, nano-clusters, and solids. In this presentation we discuss
DFT based description of the trapped dipolar fermions. The accuracy of DFT based results
crucially depends on the approximate forms of the exchange and correlation energy functionals
employed for the calculations. Recently, for dipolar Fermi gas both exchange and correlation
energy functionals within local density approximation have been derived by Liu and Yin ( Phys.
Rev. A 84, 053603 (2011)). We assess the accuracy of these exchange and correlation energy
functionals by studying a system of two harmonically trapped fermionic dipoles by using a
Hylleraas type correlated two-particle wave function.
Pinning of Hidden Vortices in Bose-Einstein Condensate
Bishwajyothi Dey
Department of Physics, University of Pune, Pune We study the vortex dynamics and vortex pinning effect in Bose-Einstein condensate in a rotating double-well trap potential and co-rotating optical lattice. We show that, in agreement with the experiment, the vortex number do not diverge when the rotational frequency approaches the trap frequency if the trap is of anisotropic double-well type. The critical rotational frequency as obtained from the numerical simulations agrees well with the value $\sqrt l/l$ for l=4 which supports the conjecture that surface modes with angular momentum l=4 are excited when the rotating condensate is trapped in double-well potential. The vortex lattice structure in a rotating triple-well trap potential and its pinning effect shows very interesting features. We show the existence and pinning of a new type of hidden vortices whose phase profile is similar to that of the visible vortices.
Validating Simple Dynamical Simulations of the Unitary Fermi Gas
Rishi Sharma Tata Institute of Fundamental Research
Mumbai Abstract : The extended Thomas Fermi (ETF) with a unitary equation of state is a useful bosonic model for the dynamics of the unitary Fermi gas and has been used to simulate collisions of clouds of unitary fermions, dynamics of topological defects like vortices, vortex rings and solitons, and to extract properties like vortex pinning off impurities. Small amplitude fluctuations have similar dynamics in the ETF and the fermionic superfluid local density approximation (SLDA) for frequencies far below the pair breaking threshold and wave vectors much smaller than the Fermi momentum. For non-linear dynamics such as vortex generation, the ETF provides a semi-quantitative description of SLDA dynamics as long as the fluctuations do not have significant power near the pair breaking threshold, otherwise the dynamics of the ETF cannot be trusted. In this talk I will compare non-linear dynamics in the two theories and show that nonlinearities in the ETF tends to generate high-frequency fluctuations, and with no normal component to remove this energy from the superfluid, features like vortex lattices cannot relax and crystallize as they do in the SLDA.
Hartree–Fock approximation for BEC revisited
Jurgen BosseFreie Universitat Berlin
Abstract:
Motivated by recent measurements of strong ground–state particle–numberfluctuations in a photon Bose–Einstein condensate [1], an effective Hamilto-nian of the single–particle type is derived for bosons in the condensed phase.As opposed to conventional HFA [2], the correlation
⟨(δN00)
2⟩
of condensed–boson number fluctuations is taken into account in addition to the averagenumber ⟨N00 ⟩ of bosons occupying the ground state when starting from thethermodynamic variational principle. For demonstration purposes, effects ofnumber fluctuation on the chemical potential are discussed for a homoge-neous system of bosons interacting via contact interaction.
References
[1] Julian Schmitt, Tobias Damm, David Dung, Frank Vewinger, Jan Klaers,and Martin Weitz. Observation of Grand-Canonical Number Statistics ina Photon Bose-Einstein Condensate. Physical Review Letters, 112:030401,2014.
[2] David A. Huse and Eric D. Siggia. The Density Distribution of a WeaklyInteracting Bose Gas in an External Potential. Journal of Low Temper-ature Physics, 46:137–149, 1982.
1
Fluctuating ground–state occupation number for trapped BEC
Jurgen BosseFreie Universitat Berlin
Abstract:
The average fraction C0 = ⟨N00 ⟩ /N of bosons condensed into the ground
state and the relative variance f0 =⟨
(δN00)2
⟩/ ⟨N00 ⟩2 of a harmonically
trapped Bose gas are calculated within thermodynamic limit approximation(TDL) using the method described in [1]. The description of interactingbosons in a trap by an effective single–particle Hamiltonian (HFA) requiresknowledge not only of C0 and f0, but also of the derivative ∂f0/∂C0. Analyt-ical results for the three quantities will be discussed for various total particlenumbers N ≫ 1 and for 0 ≤ T ≤ Tc.
References
[1] Vitaly V. Kocharovsky, Vladimir V. Kocharovsky, Martin Holthaus, C.H.Raymond Ooi, Anatoly Svidzinsky, Wolfgang Ketterle, and Marlan O.Scully. Fluctuations in ideal and interacting BOSE–EINSTEIN conden-sates: from the laser phase transition analogy to squeezed states andBOGOLIUBOV quasiparticles. In G. Rempe and M.O. Scully, editors,Advances in Atomic, Molecular, and Optical Physics, volume 53. ElsevierScience Publishers B.V., 2006.
1
Perturbative and Non-Perturbative Methodsfor Tackling the Dirty Boson Problem
Priv.-Doz. Dr. Axel Pelster
Department of Physics and Research Center OPTIMAS,
Technische Universitat Kaiserslautern, Germany
The notoriously difficult dirty boson problem amounts to understanding the emergence of coher-
ence and order for ultracold bosonic atoms in the presence of a quenched disorder potential. It
appears either naturally like in current carrying wire traps, or artificially like in laser speckle fields.
Theoretically it is intriguing because of the competition of localization and interaction as well as
of disorder and superfluidity.
We start with solving perturbatively the coupled hydrodynamic equations for a homogeneous
BEC with a weak disorder potential. In this way we reproduce the explicit expressions of Huang
and Meng for the disorder corrections of both condensate and superfluid density. In addition,
we consider a 1d ring trap and determine how the superfluid velocity depends on the disorder
correlation length.
Afterwards, we compare two non-perturbative methods, where the first one is based on a Hartree-
Fock mean-field theory by invoking replica symmetry and the second one follows from a Gaussian
approximation for correlation functions. For a homogeneous BEC we find for strong disorder
a quantum phase transition from a superfluid to a Bose-glass phase whose order changes from
second to first order for increasing disorder correlation length. Furthermore, we determine for a
harmonically trapped BEC the respective density profiles of both the global condensate and the
fragmented BECs for Lorentzian disorder.
Tuning the Quantum Phase Transition of Bosons in Optical Lattices
Priv.-Doz. Dr. Axel Pelster
Department of Physics and Research Center OPTIMAS,
Technische Universitat Kaiserslautern, Germany
Systems of ultracold bosonic gases in optical lattices have recently become a popular research topic as they
represent model systems for quantum phase transitions in solid-state physics with a yet unprecendented
level of control. For a small laser strength the bosons can tunnel from site to site and explore the whole
lattice. This leads to a superfluid state which is characterized by long-range correlations, a continuous
excitation spectrum, and a finite compressiblity. In the opposite situation of a large laser strength the
bosons can no longer tunnel to the neighboring sites, so the occupation number of the sites is fixed. This
so-called Mott phase has no long-range correlation, shows a gap in the excitation spectrum and is nearly
incompressible. At first we discuss a Ginzburg-Landau theory for the underlying Bose-Hubbard model
which allows to determine the location of the quantum phase transition from the superfluid to the Mott
phase. Afterwards we discuss two examples how this quantum phase transition can be tuned.
In the first example we consider a spinor Bose gas loaded into a three-dimensional cubic optical lattice.
There the different superfluid phases of spin-1 bosons are tunable due to the presence of an external
magnetic field. In particular at zero temperature, we determine both the Mott and the superfluid phases
for the competition between the anti-ferromagnetic interaction and the linear Zeeman effect within the
validity range of the Ginzburg-Landau theory. Moreover, we find that the phase transition between the
superfluid and Mott insulator phases is of second order and that the transitions between the respective
superfluid phases for anti-ferromagnetic interaction can be both of first and second order.
Afterwards, we discuss interacting bosons in an optical lattice with a periodic modulation of the s-
wave scattering length. At first we map the underlying periodically driven Bose-Hubbard model for
large enough driving frequencies approximately to an effective time-independent Hamiltonian with a
conditional hopping. Combining different analytical approaches with quantum Monte Carlo simulations
then reveals that the superfluid-Mott insulator quantum phase transition still exists despite the periodic
driving and that the location of the quantum phase boundary turns out to depend quite sensitively on
the driving amplitude. A more detailed quantitative analysis shows even that the effect of driving can be
described within the usual Bose-Hubbard model provided that the hopping is rescaled appropriately with
the driving amplitude. This finding indicates that the Bose-Hubbard model with a periodically driven
s-wave scattering length and the usual Bose- Hubbard model belong to the same universality class from
the point of view of critical phenomena.
Participants Abstract
Van der Waals Coefficients for the Alkali-metal Atoms in the Material Mediums
Bindiya Arora
Department of Physics, Guru Nanak Dev University, Amritsar
The C3 coefficients and their ratios for the alkali atoms are determined very accurately by taking into account the optical properties of the atoms and four distinct types of trapping materials such as Au (metal), Si (semi-conductor), vitreous SiO2 (dielectric) and SiNx(dielectric). Dynamic dipole polarizabilities are calculated precisely for the alkali atoms that produce C3coefficients in a perfectly conducting medium within 0.2% accuracy. Thus, uncertainties from the atomic polarizabilities in the evaluation of the material dependent C3 coefficients are small and accuracies of these C3
values mainly rely on the used optical data which are not accounted in the present work. Our findings are in very good agreement with the available measurements, but they differ by around 10% from the previously reported high precision calculations in heavy atoms for the perfect conductors. We also revisit the dispersion coefficients for the alkali dimers and evaluate them using the above dynamic dipole polarizabilities which provide slightly different error bars than the other reported precise results. These coefficients are fitted into a ready-to-use functional form to aid the experimentalists for finding out the interaction potential only with the knowledge of atom-wall distance.
NONLINEAR DYNAMICS OF BLOOD PRESSURE WAVES IN LARGE ELASTIC TUBES L. Kavitha1, 3, R. Ravichandran1 and D. Gopi2, 3 1Department of Physics, Periyar University, Salem, India, 2Department of Chemistry, Periyar University, Salem, India, 3Centre for Nanoscience and Nanotechnology, Periyar University, Salem, India Abstract: In this work, we investigate that it can be explored in the framework of blood flow models and behavior of the pressure pulse waves in arteries of blood flow in the mammalian arterial system. Blood is modeled as an incompressible, and the flow in the model is due to the dynamics of the prestressed thin elastic tube filled with an inviscid fluid which is considered to be one dimensional. The transient phenomena of blood flow through the arterial system are simulated by solving the one dimensional discrete nonlinear Schrödinger- type equation [1]. We show that such nonlinear model can lead to the existence of solitons moving along the arteries in the blood flow. The governing equations are solved analytically by using the Double exp function method, and found the interesting classes of soliton solutions. It is found that the critical amplitude is an increasing function of a nonlinear parameter, whereas the region of blood pressure waves are expanded [2]. A linear stability analysis is performed and found that
eigenvalues are strictly lying in the imaginary axis, confirming the stable nature of the obtained solutions [3]. From the obtained soliton solutions, blood flow in arteries is well explored and behavior of the pressure pulse waves and their biological implications of the obtained patterns are discussed.
[1] G. R. Mefire Yone, C. B. Tabi, A. Mohamadou, H. P. Ekobena Fouda, and T. C. Kofané, REFERENCES
Modulated pressure waves in large elastic tubes, Chaos 23, 033128 (2013). [2] J.F. Paquerot, M. Remoissenet. Dynamics of nonlinear blood pressure waves in large arteries, Phys. Lett. A 194 (1994) 77. [3] L. Kavitha, E. Parasuraman, M. Venkatesh, A. Mohamadou, and D. Gopi, Breather-like protonic tunneling in a discrete hydrogen bonded chain with heavy-ionic interactions, Phys. Scr. 87 (2013) 035007.
PAINLEVE INTEGRABILITY ANALYSIS AND SOLITON SOLUTION OF MULTICOMPONENT YAJIMA-OIKAWA SYSTEM K. Sakkaravarthi, K. Tamilselvan and T. Kanna Post Graduate and Research Department of Physics, Bishop Heber College, Tiruchirappalli--620017, Tamil Nadu, India Abstract:
We consider a multicomponent Yajima-Oikawa equation governing the dynamics of nonlinear resonance interaction between multiple short waves with a long wave. By applying Painleve singularity structure analysis we identify the integrability nature of the system and construct the bright multi-soliton solution by using the Hirota’s bilinearization method. Different kinds of soliton collisions, namely two types of energy sharing collisions and a standard elastic collision, are explored by performing the asymptotic analysis and demonstrated graphically. The dynamics of soliton bound states are also discussed.
EXCITATIONS OF LOCALIZED MODES VIA MODULATIONAL INSTABILITY IN CARBON NANOTUBES (CNT) WITH PRESENT AND ABSENT OF ELECTRON-PHONON INTERACTION
L. Kavithaa, b, c, E. Parasuramana, b and D. Gopi
d, b
aDepartment of Physics, Periyar University, Salem-636 011, India, bCentre for Nanoscience and Nanotechnology, Periyar University, Salem-636 011, India, cThe Abdus Salam International Centre for Theoretical Physics, Trieste, Italy, d
Department of Chemistry, Periyar University, Salem-636 011, India
Abstract: Carbon nanotube (CNT) is an ultrathin carbon fiber with nano meter size diameter and micrometer size length and was accidently discovered by Sumio Iijima in 1991. As a novel and potential carbon material, CNTs have received a great deal of attention and they posses unique properties such as mechanical, thermal, optical and electrical properties. Most properties depend crucially on the diameter, chirality and length of the tube. Some important physical properties of nanotube system are depending on the electron-phonon interaction. It is known
that such interaction results in the foundation of the nonlinear localized states such as self trapping of quasiparticles (electrons, holes or excitons), charge density waves, kinks, etc. In these states the translational symmetry of the system is spontaneously broken. Study of self-trapped states of quasiparticle, which means self consistent state of a quasiparticle and the lattice distortion, called polaron or soliton in nanotube system attract a great interest for a long time. A distortion of the lattice which is affects the energy band gap. This distortion of the lattice can be achieved in two different ways (i) through an external force like bending, stretching or twisting (ii) through an internal excitation, which interacts with a lattice. It is well known that the interaction of excitations such as amide-I-vibration in biopolymers or an electron with a lattice whose distortion is initially caused by the excitations resulting in the creation of a localized state, in what follows, we refer to as a soliton. Such a soliton was first introduced by Davydov in 1970 to explain the dispersion free energy transport in biopolymers. Recently, a Frohlich Hamiltonian was studied as a two- dimensional, discrete, quadratic lattice. The existence of localized states was studied numerically and it was formed that their properties depend crucially an electron-phonon coupling constant. They formed polaron excitations in molecular systems such as biopolymers, alpha helical proteins, etc and they studied properties of the material through localized states [1-3]. Our focus is to investigate the excitations of intrinsic localized modes via modulational instability in one-dimensional discrete carbon nanotube chain and we explain the property of the material through soliton evolution. We consider a model Hamiltonian on a hexagonal carbon nanotubes lattices to be periodic and we deduce the Hamiltonian into discrete nonlinear Schrödinger equation (DNLS) with the aid Hamilton’s equation. The investigation is made analytically in the framework of the linear stability analysis of the nonlinear plane wave solutions performed by considering the wave vector of the basic states and the wave vectors of the perturbations as free parameters. We derive a discrete nonlinear Schrödinger like equation for the spin wave motion. Using the linear stability analysis, we establish the stability/instability criterion which predicts the stability/instability region and growth rate of the modulation. The numerically analysis indicates that strength of the interaction induces the localized modes in the form of DBs via modulational instability demonstrated the play role of dispersive interactions on the existence of nanoscale DBs modes in CNT.
[1] S. Iijima, Nature 354 (1991) 56. Reference:
[2] L. Brizhik, A. Eremko, B. Piette and W. J. Zakrzewski, Physica D 146, (2000) 275. [3]L. Brizhik, B. Piette and W. J. Zakrzewski, Ukr. Fiz. Journal 46 (2001) 503.
OPTICAL PULSE PROPAGATION AT DISCRETE THIN-FILM WAVEGUIDE STRUCTURE Arvind Sharma and A.K. Nagar Department of Physics, Govt. Dungar College, Bikaner, Rajasthan 334001, India Abstract:
Keywords: thin-film nonlinear waveguide, discrete nonlinear Schrodinger equation, equivalent particle theory
The optical pulse scattering at a symmetric silica waveguide formed by the interface between two nonlinear focusing media is considered both analytically and numerically. Using the equivalent particle approach to solve the discrete nonlinear Schrodinger equation we discuss soliton reflection and transmission and so formed nonlinear surface waves both analytically and numerically.
PACS: 47.20.Ib, 02.30.Oz, 42.65.Tg, 37.10.Jk, 47.20Ky Electron acoustic solitary wave structures in quantum plasmas at finite temperature containing two kind of electrons
Swarniv Chandra1, Sibarjun Das2, Basudev Ghosh1 1Department of Physics, Jadavpur University 2
Department of FTBE, Jadavpur University
Abstract:
Using Quantum hydrodynamic (QHD Model the properties and structures of electron-acoustic waves is investigated in a three-component quantum plasma containing electrons at two different temperature and a neutralizing background of ions. Generally quantum plasmas are observed in ultra cold environments but in finite temperature also quantum phenomenon is observed. Using one such model given by Elliason and Shukla we investigate the properties of such wave by employing reductive perturbation technique and KdV equation for solitary wave propagation. It is found that the quantum diffraction parameter, finite temperature degeneracy parameter and hot to cold electron density ratio significantly influence the formation and properties of KdV solitons.
1. Amplitude modulation of electron plasma waves in a quantum plasma; Basudev Ghosh, Swarniv Chandra, and S. N. Paul; (Phys. Plasmas
References
182. Electron-acoustic solitary Waves in a relativistically Degenerate Quantum Plasma with
Two Temperature Electrons, Swarniv Chandra, Sailendra Nath Paul and Basudev Ghosh, (Astro. & Space Sci. (2012), 342, 417)
, 012106 (2011))
3. Modulatioal Instability of Electron-Acoustic Waves in Relativistically Degenerate Quantum Plasma; Swarniv Chandra and Basudev Ghosh, (Astros. &Space Sci. (2012), DOI: 10.1007/s10509-012-1186-3)
4. Nonlinear Solitary Structures of Electron Plasma Waves in a Finite Temperature Quantum Plasma, Swarniv Chandra and Basudev Ghosh; World Academy of Sci. Engg. And Tech., Vol 70, 1113, (2012)
5. Relativistic effects on the nonliner propagation of electron plasma waves in dense quantum plasma with arbitrary temperature, Swarniv Chandra and Basudev Ghosh (Int. J. of Engg. Res and Dev.3, 51 (2012))
6. Modulational Instability of Electron Plasma Waves in Finite Temperature Quantum Plasma, Swarniv Chandra and Basudev Ghosh ; World Academy of Sci. Engg. And Tech., Vol 71, 792 (2012)
7. Relativistic effects on the modulational instability of electron plasma waves in quantum plasma; Basudev Ghosh, Swarniv Chandra and Sailendra Nath Paul; Pramana-J.Phys. 78, 779-790 (2012)
8. Linear and nonlinear propagation of electron plasma waves in quantum plasma; Swarniv Chandra, Sailendra Nath Paul and Basudev Ghosh (Indian. Journal of Pure and Applied Physics, 50,314(2012))
9. Nonlinear Surface Waves on a Quantum Plasma Half-Space with Arbitrary Temperature Swarniv Chandra and Basudev Ghosh (Int. Journal of Systems, Algorithms & Appls, 3, ICASE 2013,
10. Finite Temperature Effects on the Linear Dispersion Properties of Electron-Acoustic Waves in Degenerate Plasma ; Basudev Ghosh and Swarniv Chandra (
1-3)
Int. Journal of Systems, Algorithms & Appls, 3, ICASE 2013,
11. Propagation of Electron-Acoustic Solitary Waves in Weakly Relativistically Degenerate Fermi Plasma; Swarniv Chandra, Basudev Ghosh, S.N.Paul (World Academy of Sci. Engg. And Tech., Vol 75, 726 (2013))
4-5)
Poster Presentation Abstract GROUND STATE COOLING OF MECHANICAL OSCILLATOR USING A BOSE-EINSTEIN CONDENSATE WITH BACK-ACTION COOLING AND COLD-DAMPING FEEDBACK SCHEMES Sonam Mahajan 1*, Neha Aggarwal12, Aranya B. Bhattacherjee 2,3 and Man Mohan1 1Department of Physics and Astrophysics, University of Delhi, Delhi-110007, India 2
Department of Physics, ARSD College, University of Delhi (South Campus), New Delhi-110021, India
Abstract:
We present a detailed study to show the possibility of approaching the quantum ground-state of a hybrid optomechanical quantum device formed by a Bose-Einstein condensate (BEC) confined inside a high-finesse optical cavity with an oscillatory end mirror. Cooling is achieved using two experimentally realized schemes via detuned cavity: back-action cooling and cold-damping quantum feedback cooling. In both the schemes, we found that increasing the two body interaction bring the mechanical oscillator to its quantum ground state.
STEADY STATE ANALYSIS AND PHOTODETECTION MEASUREMENTS FOR THE OPTOMECHANICAL DICKE MODEL Neha Aggarwal Department of Physics and Astrophysics, University of Delhi, Delhi-110007, India Abstract:
We present a detailed study to analyse the Dicke quantum phase transition within the thermodynamic limit for an optomechanically driven Bose-Einstein condensates in a cavity. The photodetection-based quantum optical measurements have been performed to study the dynamics and excitations of this optomechanical Dicke system. For this, we discuss the eigenvalue analysis, fluorescence spectrum and the homodyne spectrum of the system. It has been shown that the normal phase is negligibly affected by the mechanical mode of the mirror while it has a significant effect in the superradiant phase. We have observed that the eigenvalues and both the spectra exhibit distinct features that can be identified with the photonic, atomic and phononic branches. In the fluorescence spectra, we further observe an asymmetric coherent energy exchange between the three degrees of freedom of the system in the superradiant phase arising as a result of optomechanical interaction and Bloch-Siegert shift. In the semi-classical steady state analysis, an additional external mechanical pump is also shown which modifies the critical value of atom-photon coupling needed to observe the quantum phase transition. Such system can be used as a new quantum device to measure weak forces. We further show how the mechanical pump frequency and cavity-laser detuning play a significant role in producing extremely cold condensates.
THERMODYNAMICAL STUDY OF TWO-DIMENSIONAL SPIN-ORBIT-COUPLED BOSE GAS Reena Gupta Physics Department, IIT Roorkee-247667