Topological Excitations of Hidden Order in URu$_2$Si$_2$ Under Extreme Electric Fields

TL;DR

This paper demonstrates that the hidden order state in URu$_2$Si$_2$ exhibits quantum coherence effects under high electric fields, revealing a connection between microscopic order parameters and macroscopic conductivity.

Contribution

It provides evidence of non-linear conductivity linked to phase slip phenomena, indicating a complex order parameter in the hidden order phase of URu$_2$Si$_2$.

Findings

Observation of non-linear conductivity under large voltage bias

Analogy to phase slips in one-dimensional superconductors

Implication of a complex order parameter for hidden order

Abstract

Quantum materials are epitomized by the influence of collective modes upon their macroscopic properties. Relatively few examples exist, however, whereby coherence of the ground-state wavefunction directly contributes to the conductivity. Notable examples include the quantizing effects of high magnetic fields upon the 2D electron gas, the collective sliding of charge density waves subject to high electric fields, and perhaps most notably the macroscopic phase coherence that enables superconductors to carry dissipationless currents. Here we reveal that the low temperature hidden order state of URu$_2$Si$_2$ exhibits just such a connection between the quantum and macroscopic worlds -- under large voltage bias we observe non-linear contributions to the conductivity that are directly analogous to the manifestation of phase slips in one-dimensional superconductors [1], suggesting a complex order parameter for hidden order