Anomalous Transport and Possible Phase Transition in Palladium Nanojunctions

TL;DR

This study reports low-temperature anomalous conductance features in palladium nanojunctions, suggesting possible spontaneous magnetization and phase transition phenomena influenced by nanoscale structuring.

Contribution

It provides experimental evidence of magnetic-related conductance features in palladium nanojunctions and links them to potential phase transition behavior and magnetic excitations.

Findings

Sharp conductance features emerge at low temperatures.

Features depend on zero-bias conductance and temperature.

Density functional theory supports magnetization onset in nanojunctions.

Abstract

Many phenomena in condensed matter are thought to result from competition between different ordered phases. Palladium is a paramagnetic metal close to both ferromagnetism and superconductivity, and is therefore a potentially interesting material to consider. Nanoscale structuring of matter can modify relevant physical energy scales leading to effects such as locally modified magnetic interactions. We present transport measurements in electromigrated palladium break junction devices showing the emergence at low temperatures of anomalous sharp features in the differential conductance. These features appear symmetrically in applied bias and exhibit a temperature dependence of their characteristic voltages reminiscent of a mean field phase transition. The systematic variation of these voltages with zero-bias conductance, together with density functional theory calculations illustrating the relationship between the magnetization of Pd and atomic coordination, suggest that the features may result from the onset of spontaneous magnetization in the nanojunction electrodes. We propose that the characteristic conductance features are related to inelastic tunneling involving magnetic excitations.