characteristics of superconducting nanostructures Namhla Manona - - PowerPoint PPT Presentation

Computer simulation of tunneling characteristics of superconducting nanostructures

Supervisor: Dr Yury Shukrinov Co-supervisors: Ilhom Rahmonov Kirill Kulikov Laboratory of Theoretical Physics Atsile Ocwelwang

University of Fort Hare

Namhla Manona

University of Fort Hare

Nomcebo Mthombeni

University of South Africa Tshwane University of Technology

Lunga Mthayi

Walter Sisulu University

Mulatedzi Gandamipfa

University of Limpopo

7th SA-JNIR Student Practice Dubna-Russia 2013

Models of JJ systems with capacitive coupling

CCJJ CCJJ+DC Single JJ

Introduction

Diagram and equations

• The current through a system of coupled

Josephson junctions

• The current through the shunt

• The frequency of the resonant circuit with the

capacitance of Josephson junctions

Equations

Objectives

Task 1

Aim: study the effect of system parameters on the properties of Shapiro Steps(SS), when it is on rc-branch

Mulatedzi Gandamipfa

University of Limpopo

I V

0.5 1 1.5 2 4 6 8

V

0.5 1 1.5 20 40 60 80

Without shunting With shunting

I V

0.5 1 10 20 30 40 50 60

I V

0.5 1 1 2 3 4 5 6

Results: The current-voltage characteristics for a single Josephson

junction and for the system of 10 transitions.

Results

I V

0.5 1 1.5 40 60 80

I V

I V

0.5 1 1.5 20 30 40 50 60 70 80

I V

I V

0.5 1 1.5 20 30 40 50 60 70 80

Task 2

Aim: To study the appearance of the rc-branch for small and large values of capacitance

Atsile Ocwelwang

University of Fort Hare

Results

Current-Voltage characteristics (CVC) Voltage-time dependence (V(t)/t)

L= 0.2 C=1.25 Itime1=0.2 Itime2=0.8 β=0.2 N=1

Results

Current-Voltage characteristics (CVC)

Voltage-time dependence (V(t)/t)

L=45 C=0.002 Itime1=0.2 Itime2=0.8 β=0.2 N=1

Results

Low inductance (L=0.2) Large inductance (L=45)

Task 3

Nomcebo Mthombeni

University of South Africa Tshwane University of Technology

I

V

0.5 1 1 2 3 4 5 6

......................R=0 .....................R=0.25 ....................R=0.5 ....................R=1 ...................R=0.75

I

V

0.65 0.7 0.75 3.1 3.2 3.3 3.4 3.5 3.6

......................R=0 .....................R=0.25 ....................R=0.5 ....................R=1 ...................R=0.75

I

V

0.64 0.66 0.68 0.7 0.72 0.74 0.76 0.78

32 34 36

.........R=0 .........R=1 .........R=10

I

V

0.6 0.8 1

10 20 30 40 50 60

.........R=0 .........R=1 .........R=10

N=1 N=10

Results : The effect of resistance on current-voltage characteristic for lower shunt capacitance

I V

0.6 0.65 0.7 0.75

2.8 3 3.2 3.4

.......R=0 ......R=0.5 .....R=1

I V

0.4 0.6 0.8 1 1.2 20 40 60

......R = 0 ......R=1 ......R=10

I V

0.5 1

1 2 3 4 5 6

.......R=0 ......R=0.5 .....R=1

Results: The effect of resistance on current-voltage characteristic for higher shunt capacitance N=1 N=10

Task 4

Lunga Mthayi

Walter Sisulu University

zoomed v/t

N = 10 c = 1.25 A = 0.5 L = 1.0546875

• mega = 3.2 Amp

0.5 Voltage (Currant) = V/I Voltage (time) = V/t N = 10 c = 1.25 A = 0.5 L = 1.0546875

• mega = 3.2 Amp

0.5 Itime1 = 0.87 Itime2 = 0.8 Ch(time)

Results

Task 5

Namhla Manona

University of Fort Hare

V1 V2

0.5 1 1.5 20 40 60 80

V1 V2

0.6 0.65 0.7 0.75 26 28 30 32 34

Itime1= 0.54 Itime2= 0.67 zoomed Voltage(current)= V/I Voltage(time)=V/t

Results: Current-voltage characteristics and time dependence

Conclusion

• The purpose of the project was to learn about
• Systems of high temperatures superconductors
• Models of these superconductors
• Methods of how to calculate I-V characteristics,

voltage as a function of time and charge as a function

• f time
• Using these methods we obtained results that we

presented

• However we cannot conclude on these results

because it is work in progress

Acknowledgements Supervisor: Dr Yury Shukrinov Co-supervisors: Ilhom Rahmonov Kirill Kulikov Laboratory of Theoretical Physics Practice Coordinators: SA and Russia

JINR

Thank You – Spasibo