Interface superconductivity in a type-II Dirac semimetal NiTe$_2$

TL;DR

This study provides experimental evidence of interface-induced superconductivity in NiTe$_2$, a type-II Dirac semimetal, revealed through charge transport measurements showing Andreev reflection and Josephson effects at low temperatures.

Contribution

It demonstrates the emergence of superconductivity at the interface of NiTe$_2$ and gold, linked to flat-band formation and topological surface states, a novel finding in Dirac semimetals.

Findings

Observation of non-Ohmic conductance behavior at millikelvin temperatures.

Detection of Josephson current and diode effect related to topological surface states.

Superconductivity suppressed by temperature and magnetic field.

Abstract

We experimentally investigate charge transport through a single planar junction between a NiTe$_2$ Dirac semimetal and a normal gold lead. At millikelvin temperatures we observe non-Ohmic $dV/dI(V)$ behavior resembling Andreev reflection at a superconductor -- normal metal interface, while NiTe$_2$ bulk remains non-superconducting. The conclusion on superconductivity is also supported by suppression of the effect by temperature and magnetic field. In analogy with the known results for Cd$_3$As$_2$ Dirac semimetal, we connect this behavior with interfacial superconductivity due to the flat-band formation at the Au-NiTe$_2$ interface. Since the flat-band and topological surface states are closely connected, the claim on the flat-band-induced superconductivity is also supported by the Josephson current through the topological surface states on the pristine NiTe$_2$ surface. We demonstrate the pronounced Josephson diode effect, which results from the momentum shift of topological surface states of NiTe$_2$ under an in-plane magnetic field.