# Suppression of the superconductivity in ultrathin amorphous Mo$_{78}$Ge$_{22}$ thin films observed by STM

## TL;DR

This study investigates how ultrathin amorphous MoGe films suppress superconductivity when in contact with gold, revealing a strong pair-breaking effect at the interface through STM measurements of local density of states.

## Contribution

It provides detailed STM analysis of the proximity effect and superconductivity suppression in ultrathin MoGe films on gold, highlighting the impact of interface-induced pair-breaking.

## Key findings

- Superconducting gap decreases with thinner MoGe layers.
- Almost complete suppression of coherence peaks in 5 nm MoGe.
- Strong pair-breaking effects due to spin-flip processes at the interface.

## Abstract

In contact with a superconductor, a normal metal modifies its properties due to Andreev reflection. In the current work, the local density of states (LDOS) of superconductor - normal metal Mo$_{78}$Ge$_{22}$ - Au bilayers are studied by means of STM applied from the Au side. Three bilayers have been prepared on silicate glass substrate consisting of 100, 10 and 5 nm MoGe thin films covered always by 5 nm Au layer. The tunneling spectra were measured at temperatures from 0.5 K to 7 K. The two-dimensional cross-correlation between topography and normalized zero-bias conductance (ZBC) indicates a proximity effect between 100 and 10 nm MoGe thin films and Au layer where a superconducting gap slightly smaller than that of bulk MoGe is observed. The effect of the thinnest 5 nm MoGe layer on Au leads to much smaller gap moreover the LDOS reveals almost completely suppressed coherence peaks. This is attributed to a strong pair-breaking effect of spin-flip processes at the interface between MoGe films and the substrate.