Gapped Excitations in the High-Pressure Antiferromagnetic Phase of URu$_2$Si$_2$

TL;DR

This neutron scattering study investigates the magnetic excitations in URu$_2$Si$_2$ across different phases induced by temperature and pressure, revealing consistent excitation spectra but an increased energy gap under pressure.

Contribution

The paper provides the first detailed characterization of magnetic excitations in the high-pressure antiferromagnetic phase of URu$_2$Si$_2$, highlighting changes in the excitation gap.

Findings

Excitations are similar across hidden order and large moment phases.

The energy gap at the $ ext{Σ}$ point increases from 4.2 meV to 5.5 meV under pressure.

No change in excitation widths at key points within experimental resolution.

Abstract

We report a neutron scattering study of the magnetic excitation spectrum in each of the three temperature and pressure driven phases of URu$_2$Si$_2$. We find qualitatively similar excitations throughout the (H0L) scattering plane in the hidden order and large moment phases, with no changes in the $\hbar\omega$-widths of the excitations at the $\Sigma$ = (1.407,0,0) and $Z$ = (1,0,0) points, within our experimental resolution. There is, however, an increase in the gap at the $\Sigma$ point from 4.2(2) meV to 5.5(3) meV, consistent with other indicators of enhanced antiferromagnetism under pressure.