Proximity-induced superconducting gap in the intrinsic magnetic topological insulator MnBi2Te4

TL;DR

This study demonstrates a proximity-induced superconducting gap in MnBi2Te4, a magnetic topological insulator, influenced by magnetic field and Fermi level tuning, revealing interplay between magnetism and superconductivity relevant for topological quantum states.

Contribution

It provides experimental evidence of a superconducting gap induced in MnBi2Te4 and explores how it is affected by magnetic field and Fermi level tuning, advancing understanding of topological superconductivity.

Findings

Proximity-induced superconducting gap of 0.1 meV observed.

Gap enhanced by tuning Fermi level toward charge neutrality.

Magnetic field can anomalously enhance the induced gap.

Abstract

We report magnetotransport measurements in the NbN/ magnetic topological insulator MnBi2Te4 (MBT)/ NbN junction at low temperature. At 10 mK, the nonlinear current-voltage characteristic of the junction shows a tunneling behavior, indicating the existence of interfacial potential barriers within the heterostructure. Under an out of plane perpendicular magnetic field, a transition from negative to positive magnetoresistance (MR) is found when increasing the bias voltage. A proximity-induced superconducting gap is estimated to be 0.1meV by a pair of differential resistance dips. Moreover, the induced gap is enhanced by gradually tuning the Fermi level toward the charge neutral point by a back gate voltage, which is ascribed to the increased transport contribution of the topological surface states in MBT. Intriguingly, the induced gap exhibits an anomalous magnetic field assisted enhancement, which may originate from the spin orbit coupling and magnetic order of MBT. Our results reveal the interplay between magnetism and superconductivity in MBT, paving the way for further studies on topological superconductivity and chiral Majorana edge modes in quantum anomalous Hall insulator/superconductor hybrid systems.