Supercurrent switch in π topological junctions based upon a narrow quantum spin Hall insulator

Abstract

The narrow quantum spin Hall (QSH) insulator is characterized by interedge coupling, which could feature exotic transport phenomena, and thus serves as the key element for topological superconducting electronic devices. Herein, we theoretically explore possible Josephson π states in a QSH insulator strip touching on two s-wave superconductors in the presence of the interedge coupling. It is shown that the interedge coupling could give rise to a 0 − π transition modulated by the gate voltage, originating from an additional π phase difference caused by the interedge backscattering. The 0 − π transition in turn can manifest the helical spin texture of the edge states. A considerable residual value of the supercurrent at the 0 − π transition point is always exhibited, suggesting a very efficient performance of the device as a supercurrent switch. Moreover, the region of coexisting 0 and π states is found fairly large, which can be used to improve accuracy in the design of a π superconducting quantum interference device.

Transport in two-dimensional topological materials: recent developments in experiment and theory

“…The difficulty is that the equilibrium CPR ( 67) is 2π periodic, as the two contributions there simply swap upon a 2π phase advance. Although the fractional JE cannot be easily inferred from such equilibrium CPRs, they, nevertheless, diagnose unconventional superconductivity in topological materials which has become a subject of intense effort on its own [443,526,527,500,528,529,530,531,532,533,534,535,536,537,538,539,540,541,542,543,544,545,546,425,458,547,548,549]. In order to trace the fractional JE at equilibrium, one may look at the effect of external magnetic field.…”

Spontaneous supercurrent and φ0 phase shift parallel to magnetized topological insulator interfaces

“…The spin direction of a moving particle at the surface of a three-dimensional (3D) TI in the presence of time-reversal symmetry is rigidly locked to its momentum direction 1,2 . Due to the spin-momentum locking phenomenon, the induction of superconductivity and magnetism in the surface of a TI is predicted to serve as an unprecedented condensed matter platform that supports odd-frequency, topological superconductivity, and Majorana fermions [3][4][5][6][7][8][9][10][11][12] . In order to fabricate superconducting and magnetic surface states, one can proximitize the surface channels with a superconductor and ferromagnet, respectively 14,15 .…”

Superconductivity switch from spin-singlet to -triplet pairing in a topological superconducting junction

“…The spin-up and spin-down carriers of the same edge in the helical edge states run strictly toward opposite directions [2], indicating that the intraedge backscattering is thoroughly suppressed. Resultantly, the edge states have important applications in topological spintronic device and quantum information processing such as the promising creator and detector for entangled electron pairs [6,7]. Besides, though the edge-state conduction and the spin polarization of the edge current have been confirmed, a direct evidence for the helical spin texture of the edge states lacks enough.…”