Proximity‐Effect‐Induced Superconductivity in Nb/Sb₂Te₃‐Nanoribbon/Nb Junctions

Abstract

Nanohybrid superconducting junctions using antimony telluride (Sb 2 Te 3) topological insulator nanoribbons and Nb superconducting electrodes are fabricated using electron beam lithography and magnetron sputtering. The effects of bias current, temperature, and magnetic field on the transport properties of the junctions in a four-terminal measurement configuration are investigated. Two features are observed. First, the formation of a Josephson weak-link junction. The junction is formed by proximity-induced areas in the nanoribbon right underneath the inner Nb electrodes which are connected by the few tens of nanometers short Sb 2 Te 3 bridge. At 0.5 K a critical current of 0.15 µA is observed. The decrease of the supercurrent with temperature is explained in the framework of a diffusive junction. Furthermore, the Josephson supercurrent is found to decrease monotonously with the magnetic field indicating that the structure is in the small-junction limit. As a second feature, a transition is also observed in the differential resistance at larger bias currents and larger magnetic fields, which is attributed to the suppression of the proximity-induced superconductive state in the nanoribbon area underneath the Nb electrodes.

Flux periodic oscillations and phase-coherent transport in GeTe nanowire-based devices

“…Moreover, there is another drop in the temperature region between 1.0 and 2.0 K, which is assigned to the superconducting transition temperature T c,NW of the Nb/GeTe-NW/Nb junction. The two-step feature has been observed before in Josephson junctions with a normal metal 53 and a semiconductor weak link 54 as well as in topological insulator-based junctions 55 . The normal state four-terminal resistance ( R N ) of the present Nb/GeTe-NW/Nb junction is about 355 Ω at temperatures above T c,Nb .…”

“…The temperature and magnetic field dependent I − V characteristics and d V /d I curves were measured using a standard lock-in technology in a 3 He cryostat with a base temperature of 0.4 K and a magnetic field range from −8 to 8 T. A four-terminal current driven geometry is employed to directly measuring the voltage drop across the inner section of GeTe nanowire between the nearest internal electrodes. The external pair of electrodes was used for current bias 55 . The differential resistance (d V /d I ) is gained by superimposing a small AC current of 10 nA at 9.4 Hz on a DC bias current.…”

Flux periodic oscillations and phase-coherent transport in GeTe nanowire-based devices

“…The two-step feature has been observed before in normal metal, 51 in semiconductor-based Josephson junctions, 52 as well as in topological insulator based junctions. 53 The normal state four-terminal resistance (R N ) of the present Nb/GeTe-NW/Nb junction is about 355 Ω at temperatures above T c,Nb .…”

“…The external pair of electrodes was used for current bias. 53 The differential resistance (dV/dI ) is gained by superimposing a small AC current of 10 nA at 9.4 Hz on a DC bias current. Note that the applied bias current should be as small as possible to avoid electron heating and damage of the GeTe-based nanodevices.…”

Spin–momentum locking induced non-local voltage in topological insulator nanowire

“…Our previous studies on the nanowires have revealed the single crystalline structure with repeating quintuple layers of (Te-Sb-Te-Sb-Te). [25][26][27] We have also performed low temperature magnetoresistance measurements and angle resolved photoemission spectroscopy on these nanowires synthesized by the same setup as presented in this work. The periodic Aharonov-Bohm type oscillations observed manifest the transport in topologically protected surface states in the p-type Sb2Te3 nanowires, with a Fermi level positioned approximately 40 meV below the -point.…”