EFFECT OF DIFFUSION CURRENT (DC) ON CAPACTIVELY COUPLED JOSEPHSON JUNCTIONS (CCJJ)

COMPARATIVE STUDY BETWEEN CCJJ AND CCJJ+DCCOMPARATIVE STUDY BETWEEN CCJJ AND CCJJ+DC

Practice of students from ARAB REPUBLIC OF EGYPTARAB REPUBLIC OF EGYPT

20092009

PROJECT

• TITLE: Comparative Study between CCJJ and CCJJ+DCComparative Study between CCJJ and CCJJ+DC

• STUDENTS: Mostafa El DemeryMostafa El Demery

• SUPERVISOR: DRDR. Yuri ShukrinovYuri Shukrinov

• LAB: Bogoliubov Laboratory of Theoretical Physics Bogoliubov Laboratory of Theoretical Physics (BLTP)(BLTP)

LAYOUT• Some History

• Josephson Effect

• Josephson Junctions

• Capacitively Coupled Josephson Junctions

• Our Investigation

Some History• 1911: Onnes discovered SuperconductivitySuperconductivity.

• 1933: Meissner and Ochsenfeld discovered the perfect diamagnetismperfect diamagnetism.

• 1950: London, Ginsburg and Landau formulated a phenomenological theories of Superconductivityphenomenological theories of Superconductivity.

• 1957: Bardeen, Cooper and Schrieffer formulated a microscopic theories of Superconductivitymicroscopic theories of Superconductivity.

Some History

• 1962: Josephson effect Josephson effect and Josephson Josephson JunctionsJunctions.

• 1963: Anderson experimentally verified SupercurrentSupercurrent to be existed.

Josephson Effect• Novel phenomena should arise in a weak electrical

contact between two superconductors (Josephson Junction).

• Supercurrent component in the net current flowing through the junction is responsible for these phenomena.

• Supercurrent is a function not of the voltage V across the junction but of the phase-difference Josephson PhaseJosephson Phase.

Josephson Junction

Jose

phso

n Eff

ect

Josephson JunctionsTypes

TypesTypes• Tunnel Junctions (SIS Sandwich)1. Proposed in 1960 by Giaever.2. Superconductor (S)-insulator (I)-superconductor (S).3. Electrons have a small but nonvanishing probability

of penetrating from one electrode to the other one via quantum tunneling through the energy barrier by the insulator.

4. Electron penetration results in a nonvanishing normal conductance Gn when the electrodes are in

Normal State Superconducting State

S SI

Tunnel Junction

S S

N

Weak Link

Josephson JunctionsTypes (cont.)

TypesTypes• Weak Link (SNS Sandwich)

Capacitively Coupled Josephson Junctions

• System of superconducting layers with indices l and order parameter

and time-dependent phase

• Gauge invariant phase difference

Capacitively Coupled Josephson Junctions

• Generalized Josephson Relation GJR

• α is the coupling constant between junctions.

Comparative Study between CCJJ and CCJJ+DCComparative Study between CCJJ and CCJJ+DC

CCJJ• Total current flowing

through junctions is

CCJJ+DC• Total current flowing

through junctions is

System of dynamical equations for the phase difference

Comparative Study between CCJJ and CCJJ+DC (Cont.)Comparative Study between CCJJ and CCJJ+DC (Cont.)CCJJ

CCJJ+DC

With

out N

oise

P

erio

dic

BCs

W

ith N

oise

Comparative Study between CCJJ and CCJJ+DC (Cont.)Comparative Study between CCJJ and CCJJ+DC (Cont.)CCJJ

CCJJ+DC

With

out N

oise

Non

Per

iodi

c BC

s

W

ith N

oise

Comparative Study between CCJJ and CCJJ+DC (Cont.)Comparative Study between CCJJ and CCJJ+DC (Cont.)CCJJ

CCJJ+DC

Interjunction coupling between IJJInterjunction coupling between IJJCCJJ

Thank you for attention

Acknowledgement