Quantum oscillations in a hexagonal boron nitride-supported single crystalline InSb nanosheet

A gated Hall-bar device is made from an epitaxially grown,free-standing InSb nanosheet on a hexagonal boron nitride(hBN)dielectric/graphite gate structure and the electron transport properties in the InSb nanosheet are studied by gate-transfer characteristic and magnetotransport measurements at low temperatures.The measurements show that the carriers in the InSb nanosheet are of electrons and the carrier density in the nanosheet can be highly efficiently tuned by the graphite gate.The mobility of the electrons in the InSb nanosheet is extracted from low-field magneotransport measurements and a value of the mobility exceeding~1.8×10^(4) cm^(2)·V^(-1)·s^(-1) is found.High-field magentotransport measurements show well-defined Shubnikov-de Haas(SdH)oscillations in the longitudinal resistance of the InSb nanosheet.Temperature-dependent measurements of the SdH oscillations are carried out and key transport parameters,including the electron effective mass m*~0.028m0 and the quantum lifetimeτ~0.046 ps,in the InSb nanosheet are extracted.It is for the first time that such experimental measurements have been reported for a free-standing InSb nanosheet and the results obtained indicate that InSb nanosheet/hBN/graphite gate structures can be used to develop advanced quantum devices for novel physics studies and for quantum technology applications.

Anomalous negative magnetoresistance in quantum dot Josephson junctions with Kondo correlations

The interplay between superconductivity and the Kondo effect has stimulated significant interest in condensed matter physics.They compete when their critical temperatures are close and can give rise to a quantum phase transition that can mimic Majorana zero modes.Here,we have fabricated and measured Al-InSb nanowire quantum dot-Al devices.In the Kondo regime,a supercurrent-induced zero-bias conductance peak emerges.This zero-bias peak shows an anomalous negative magnetoresistance(NMR)at weak magnetic fields.We attribute this anomalous NMR to quasiparticle trapping at vortices in the superconductor leads as a weak magnetic field is applied.The trapping effect lowers the quasiparticle-caused dissipation and thus enhances the Josephson current.This work connects the vortex physics and the supercurrent tunneling in Kondo regimes and can help further understand the physics of Josephson quantum dot system.