ipcms - dmons post-docs: jérôme roccia (dmons-don) guillaume weick physique mesoscopique physique...
TRANSCRIPT
IPCMS - DMONS
Post-docs: Jérôme Roccia (DMONS-DON)
Guillaume Weick
PHYSIQUE MESOSCOPIQUEPHYSIQUE MESOSCOPIQUE
Rodolfo JalabertDietmar Weinmann
Etudiants: Guido Intronati (Strasbourg – Buenos Aires)
Wojciech Szewc
Conductance à travers de systèmes fortement corrélésRelaxation du spin
Transport dépendant de spin Nanoparticules métalliques
Electronique moléculaire (G.W.) Courants permanents et interactions (D.W.)
Décohérence et dissipation (R.J.)
Domaines de recherche :
Conductance à travers de systèmes fortement corrélés
individual object
universality
size
interactionsnon-local
effects
nano
Quantum transport
- Separation of sample, leads and reservoirs - Mean field, quasi-particle scattering states at the Fermi energy - Equilibration in the reservoirs leads to dissipation - Contact resistance
Two terminal conductance:
Landauer: conductance from scattering
Conductance through an interacting region
- How do we calculate the transmission coefficient T ?
- Is the scattering approach still valid ?
without inelastic process (zero temperature)
persistent current for interacting region + leads
embedding method
Ground-state property!
Numerical implementation
Conductance through a correlated region
g decreases with U
g decreases with LS
Mott insulator
g ≈ 1 for LS odd
Perfect conductance only with adiabatic contacts
W = 0
Even-odd asymmetry and Coulomb blockade
LS odd: Resonance NS NS +1 electrons in the interacting region Coulomb blockade resonance (half filling)LS even: Transport involves charging energy U Interacting region is a barrier
Observation of a parity oscillation in the conductance of atomic wires:
R.H.M. Smit, et al, PRL ’03
Fabry-Perot interference in a nanotube electron waveguideLlang, et al, Nature ’01.
Can we describe an interacting region by an effective one-particle scatterer?
R = R+ +
R-
R ≠ R+ +
R-
Quantum mechanics, non-locality
S = S+ * S-
Electron-electron interactions
S+ S-
S ≠ S+ *
S-
non local effect !
ohmic composition
Interaction-induced non-local effects
universal correction!
D.A. Wharam et al, J. Phys. C, 1988
Conductance quantization in a point contact
M.A. Topinka et al, Nature, 2001 0.7 anomaly
Nanoparticules métalliques
in a metal:
MIE THEORYMIE THEORY On the color of gold colloids -
1908
λ >> 2a
resonance pour surface plasmon
Bréchignac et al, PRL 1993
(visible)
Photo-absorption cross section of 12C nucleus
Plasmon resonance in free clusters
Differential transmission
Bigot et al., Chem. Phys., 2000
(ps)
(eV)
pscorrelated electrons
collective modesnonthermal regime
e-e & e-surface scattering,
thermal distribution
e-phonons scatteringrelaxation to the lattice
cooling of the distribution
energy transfer to the matrix
TIME RESOLVED EXPERIMENTS, POMP-PROBETIME RESOLVED EXPERIMENTS, POMP-PROBE
pspsps
One-particle potential: uniform
jellium background with a
Coulomb tail
COLLECTIVE AND RELATIVE COORDINATESCOLLECTIVE AND RELATIVE COORDINATES
center of mass: harmonic oscillator
plasmonplasmon
relative coordinates: mean field
coupling: dipole field
Kawabata & Kubo, 1966
Time-Dependent Local Density Approximation
Nonmonotonic behavior !!
Na
SIZE-OSCILLATIONS OF THE LINEWIDTHSIZE-OSCILLATIONS OF THE LINEWIDTH
Drude, Drude, τ‾τ‾11
confinement, confinement, aa << ττ vvFF
Semiclassical approach
PLASMON AS A COLLECTIVE EXCITATION PLASMON AS A COLLECTIVE EXCITATION
RPA eigenenergies :
PlasmonPlasmon = superposition of low-energy e-hlow-energy e-h coupled to
high-energy high-energy e-he-h
restricted subspace
additional subspace
dipole absorption cross-section
SPIN DIPOLE EXCITATIONSPIN DIPOLE EXCITATION
Décohérence et dissipation
HH -H-H
Spin echo (Hahn)
Loschmidt echoLoschmidt echo (fidelity) in the presence of a weak coupling to the environment
||00
||HH00tt
MM(t) = (t) = ||00| exp[+| exp[+i(i(HH00++))tt] exp[-] exp[-iiHH00tt] |] |00||22
HH00HH00
- H- H
||HH00 ,, - -H H 2t2t
||HH00tt||HHtt
||00
HH
H=HH=H00++environmentenvironment
How does How does MM(t)(t) depend on depend on HH00 ,, , and, and t t ? ?
Time-reversal focusing
C. Draeger, M. Fink, PRL 1997