Andreev reflection for MnTe altermagnet candidate

TL;DR

This study demonstrates Andreev reflection in MnTe altermagnet junctions, revealing unique transport properties that suggest less disorder impact compared to normal metals, with implications for spintronic applications.

Contribution

First experimental observation of Andreev reflection in MnTe altermagnet, highlighting its robustness against disorder and expanding understanding of altermagnetic transport phenomena.

Findings

Andreev reflection observed at high junction resistance

Suppression of Andreev features in magnetic field

Universal behavior across samples

Abstract

We experimentally study electron transport across a single planar junction between the indium electrode and MnTe altermagnet candidate. We confirm standard Ohmic behavior with strictly linear current-voltage curves above the indium critical field or temperature, although with high, about 100~kOhm, junction resistance. At low temperatures and in zero magnetic field, we observe a well-developed Andreev curve with the pronounced coherence peaks, which cannot be normally expected for these high values of normal junction resistance. The conclusion on the Andreev reflection is also supported by suppression in magnetic field, as well as by universality of the observed behavior for all of the investigated samples. The experimental results can be explained by specifics of Andreev transport through the disordered region at the superconductor-altermagnet interface. Due to a different set of restrictions on the possibility of Andreev reflection, an altermagnet suffers from the presence of disorder less than a normal spin-degenerate metal, so the conductance enhancement is retained throughout the superconducting gap.