Superconducting devices based on coherent operation of Josephson junction arrays above 77K

Transcription

1 Electronic Devices, Invited talk, ISS 2017, Tokyo, Japan Superconducting devices based on coherent operation of Josephson junction arrays above 77K Boris Chesca Physics Department, Loughborough University, UK Collaborators Loughborough University Experimental: PhD/postdoc, Daniel John Dr. Marat Gaifullin Master students: Matthew Kemp, Jeffrey Brown, Richard Pollett Theory: PhD Jonathan Cox, Prof. Sergey Savelev Nottingham University: Christopher Mellor 1

2 Outline 77 K better than 4.2 K First flux-flow microwave 77K Josephson vortex-flow transistors with record 77K reversible flux-flow ratchets 2

3 77 K better than 4.2 K 3

4 SQUID SQUID arrays N SQUID array B. Chesca, American Institute of Physics, press release October 2015: Noise Array = N 1/2 Noise SQUID V Array = N V SQUID [ ] Array N 1/2 ]SQUID [ Noise 1 Noise = V V flux coherent & non-interacting SQUID array 4

5 V Array = N V SQUID, small arrays (N=10) V Array = N V SQUID true for 2 SQUIDs 2 SQUIDs 1 SQUID V Array = N V SQUID NOT true for 10 SQUIDs! 10 SQUIDs 1 SQUID Chiu-Hsien Wu et al, J. Appl. Phys. 100, (2006); 5

6 V Array = N V SQUID, small arrays (N=10) V Array = N V SQUID true for 10 SQUIDs but SQUIDs are too large; this design is not suitable for large N! C. H. Wu et al, Supercond. Sci. Technol. 19, S246 (2006) 6

7 Large SQUID arrays (N=484, 770) B. Chesca, D. John, C. Mellor, Appl. Phys. Lett. 107, (2015) International Patent, PCT: B. Chesca, D. John, WO A1(2017) 7

8 SQUID 77K better than 4.2 K -5 Voltage V, mv series SQUID array T=83K, V max =6.8 mv (b) -172 A -212 A Applied magnetic field B, T 10 S 1/2 ( Hz1/2 ) K K 1/N 1/2 Max ( V), mv Number of SQUIDs Number of SQUIDs 5 HTS 77 K nano-hts 4.2 K LTS 4.2 K B. Chesca, D. John, C. Mellor, Appl. Phys. Lett. 107, (2015); D. Castelvecchi and B. Chesca, Nature, Research Highlights 526, 613 (2015). 8

9 First flux-flow microwave 77K 9

10 10x10 JJ array as tunable microwave 4.2K GHz P. A. A. Booi, and S. P. Benz, Appl. Phys. Lett. 64, 2163 (1994) 10

11 Flux-flow resonances in asymmetric 440 JJ arrays B-field tunable power of about 0.1 µw within the range (1.5-25) 77K 1.0 P=0.5(I I step /I c ) 2 R N /N Flux-flow resonances T=77K, 15 IVCs Current, I (ma) 0.5 m=2 asymmetric array 22 x 20 JJ B YBCO (a) set of 20 JJ 20 m Voltage, V ( V) B. Chesca, D. John, C. Mellor, Supercond. Sci. Technol. 27, (2014) I V 11

12 Flux-flow resonances in asymmetric 440 JJ arrays 1.0 Array of 22 x 20 JJ T=84 K IVCs: 1-16 m=1 Current (ma) 0.5 m=3 m=4 Voltage, V/I C R N m=4 m=1 m=4 m= (b) ex Voltage ( V) B. Chesca, D. John, C. Mellor, Supercond. Sci. Technol. 27, (2014) 12

13 Josephson vortex-flow transistors (JVFT) with record 77K 13

14 Previous JVFT designs: asymmetrical bias current Small symmetrical arrays (6JJ), maximum current 77K: 3.5 R. Gross, et.al, Appl. Supercond. 3, 443 (1995) 14

15 1.0 4 IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), February Anomalous flux-flow in large asymmetric arrays Large asymmetrical arrays (440 JJ) maximum current 77K: Current (ma) g max =0.28mA/15 A=19 Maximum Current Gain Parallel array of 22 x 20 JJ T=77K Voltage ( V) gmax (T) Temperature (K) B. Chesca, D. John, C. Mellor, Appl. Phys. Lett. 103, (2013) 15

16 Current amplification in large asymmetric arrays Critical Current, I c (ma) Parallel array of 22 x 20 JJ T=77 K g max = V -0.2 V -0.3 V -0.4 V -0.5 V -0.6 V -0.7 V Critical Current, I c (ma) Parallel array of 22 x 20 JJ T=77 K 0.7 V 0.6 V 0.5 V 0.4 V 0.3 V 0.2 V 0.1 V g max = (b) 0.4 (a) Control Current, I ctrl (ma) Control Current, I ctrl (ma) B. Chesca, D. John, C. Mellor, Appl. Phys. Lett. 103, (2013) 16

17 Reversible flux-flow ratchets 17

18 Which ratchet? 100% Symmetric J c, asymmetric A 10 JJ array Simulations (a) Symmetric j c & A Asymmetric j c & A Asymmetric J c, symmetric A Magnetic Field, 0 /S 1 B. Chesca, D. John, R. Pollett, M. Gaifullin, J. Cox, C. Mellor, S. Savelev, Appl. Phys. Lett. 111, (2017). 18

19 Reversible flux-flow ratchets ex JJ array, sample A T=89K 40 I=-100 A, 100 A, sample A 20 0 Voltage, V I, A T=89K B=4 T V, V I, A T=89K 221 IVs -300 B=(-37 T, 37 T) V, V B, T I=-100 A, 100 A, sample B A -100 A B, T B, T B. Chesca, D. John, R. Pollett, M. Gaifullin, J. Cox, C. Mellor, S. Savelev, Appl. Phys. Lett. 111, (2017). 19

20 Conclusions Remarkable performances shown by very large arrays-based 77K series arrays: magnetometers asymmetric parallel arrays: flux-flow microwave generators transistors reversible ratchets Great potential to replace single-jj or single-squid based 4.2K performance can be further improved by optimization 20