Absence of superconductivity in ultra-thin layers of FeSe synthesized on a topological insulator

TL;DR

This study investigates ultra-thin FeSe layers on Bi2Se3, finding no evidence of superconductivity down to 5 K despite structural similarities to other FeSe systems.

Contribution

It provides the first detailed electronic and structural analysis of FeSe on a topological insulator, revealing the absence of superconductivity in these ultra-thin layers.

Findings

FeSe layers are 3-5 monolayers thick with similar electronic features to those on SrTiO3.

The topological state of Bi2Se3 remains intact beneath FeSe layers.

No superconducting gap observed down to 5 K in STS measurements.

Abstract

The structural and electronic properties of FeSe ultra-thin layers on Bi$_{2}$Se$_{3}$ have been investigated with a combination of scanning tunneling microscopy and spectroscopy and angle-resolved photoemission spectroscopy. The FeSe multi-layers, which are predominantly 3-5 monolayers (ML) thick, exhibit a hole pocket-like electron band at \bar{\Gamma} and a dumbbell-like feature at \bar{M}, similar to multi-layers of FeSe on SrTiO$_{3}$. Moreover, the topological state of the Bi2Se3 is preserved beneath the FeSe layer, as indicated by a heavily \it{n}-doped Dirac cone. Low temperature STS does not exhibit a superconducting gap for any investigated thickness down to a temperature of 5 K.