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

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

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

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. Q l =Q 0  (V l+1 -V l ) Q 0 =   0 V 0 /r D 2 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 (I R )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 β IRIR

14. Alternating take off critical current (Ic) 1 2 9 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 J c of the system is varied, the system will take the lowest J c to be its own critical current.

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

17. THANK YOU