Josephson supercurrent in a topological insulator without a bulk shunt

Abstract

Abstract. A Josephson supercurrent has been induced into the three-dimensional topological insulator Bi 1.5 Sb 0.5 Te 1.7 Se 1.3 .We show that the transport in Bi 1.5 Sb 0.5 Te 1.7 Se 1.3 exfoliated flakes is dominated by surface states and that the bulk conductivity can be neglected at the temperatures where we study the proximity induced superconductivity. We prepared Josephson junctions with widths in the order of 40 nm and lengths in the order of 50 to 80 nm on several Bi 1.5 Sb 0.5 Te 1.7 Se 1.3 flakes and measured down to 30 mK. The Fraunhofer patterns unequivocally reveal that the supercurrent is a Josephson supercurrent. The measured critical currents are reproducibly observed on different devices and upon multiple cooldowns, and the critical current dependence on temperature as well as magnetic field can be well explained by diffusive transport models and geometric effects. ‡ Current address:

Tunneling spectroscopy and Josephson current of superconductor-ferromagnet hybrids on the surface of a 3D TI

“…It is also interesting to notice that in the large area of low temperature, J c is nearly a linear function of T in both short-and longjunction. This result is in good agreement with the recent experiments in long Nb/Bi 1.5 Sb 0.5 Te 1.7 Se 1.3 /Nb Josephson junction [46]. In Figs.5(e) and (f), we plot the length dependence of Josephson current.…”

Conductance oscillations and zero-bias anomaly in a single superconducting junction to a three-dimensional Bi 2 Te 3 topological insulator

“…It should be defined by Thouless energy ∆ ind ∼ E T h (see Appendix to Ref. 38 for recent comprehensive discussion), which is defined as E T h ∼hv F /L in the regime of ballistic transport 44 . Obviously, it gives L values of the same order that we have from the oscillation periods in Fig.3 (a).…”

Nonsinusoidal Current-Phase Relationship in Josephson Junctions from the 3D Topological Insulator HgTe

“…These special properties are reflected in the superconducting proximity effect in an S/3D-TI bilayer or an S/TI/S junction, which may host Majorana fermions in a quasi-1D channel or vortex core [8][9][10]. Most previous works characterized current-voltage characteristics to determine the critical current's dependence on temperature, gate voltage, or magnetic field [11][12][13][14][15][16][17][18][19][20][21][22], while a few studies characterized the CPR [23,24].Here, we use a scanning SQUID microscope to perform contactless measurements of the diamagnetic response of Nb/HgTe bilayers and of the CPR of Nb/HgTe/Nb junctions. In contrast to previous CPR results [23,24], we find no evidence for bulk states, 2 and we observe that the CPRs of many junctions of different sizes consistently exhibit forward skewness.…”

“…These special properties are reflected in the superconducting proximity effect in an S/3D-TI bilayer or an S/TI/S junction, which may host Majorana fermions in a quasi-1D channel or vortex core [8][9][10]. Most previous works characterized current-voltage characteristics to determine the critical current's dependence on temperature, gate voltage, or magnetic field [11][12][13][14][15][16][17][18][19][20][21][22], while a few studies characterized the CPR [23,24].…”