COMPUTER SIMULATION OF TUNNELING CHARACTERISTICS OF SUPERCONDUCTING NANOSTRUCTURES.

1. COMPUTER SIMULATION OF TUNNELING CHARACTERISTICS OF SUPERCONDUCTING NANOSTRUCTURES. Ntombizikhona Ndlovu, Lynndle Maasdorp, Bheki Zulu (BLTP) 2010 SA STUDENT SUMMER PRACTISE 23 September 2010

2. INTRODUCTION Superconductor (SC) Superconduvtivity • SC → material that conducts electric current without any energy loss (theoritical) • Resistivity (ρ) ≈ 0 T< Tc H< Hc ρ ≈ ρ0 T> Tc H< Hc

4. JOSEPHSON JUNCTION (JJ) S I • JJ → arrangement of 2 SC linked by an insulating layer • Current (I) can pass through the insulator by means of tunneling cooper pairs of electron

5. CAPACITIVE COUPLING JOSEPHSON JUNCTION (CCJJ) v CCJJ Model CCJJ+DC

6. CCJJ Model for Varying β values

7. CVC for β = 0.05 A breakpoint current is determined by the creation of the longitudinal plasma waves with a definite wave number k, which depends on the coupling parameter α, the dissipation parameter β, the number of junctions in the stack and the boundary conditions

9. Ql=Q0 (Vl+1-Vl)Q0 = 0 V0/rD2 , , Resonance occurs when a breakpoint occurs. For Longitudinal Plasma Waves (LPW)

10. Profile of time dependence of the charge in a stack with 10 IJJ

11. Investigation of the β effects on the critical return current (IR)for different β values between 0.01 and 0.1 with Δβ=0.02 for a fixed α value (α=1) in CCJJ model

12. IVC for diff. beta values

13. Return Current Vs Beta IR β

14. Alternating take off critical current (Ic) 1 9 2 Ic alternating between 1 and 0.5

15. CONCLUSION • Junction charge at breakpoints (correspondence b/t Q oscillations and IVC curve) • Ir increase with β • IVC→ when Jc of the system is varied, the system will • take the lowest Jc to be its own critical current.

16. ACKNOWLEDGEMENTS 1 .Yury Shukrivov 2. Ilhom Rahmonov 3. Magmud Gaffar

17. THANK YOU