Hybridization gap and anisotropic far-infrared optical conductivity of URu2Si2

TL;DR

This study investigates the anisotropic far-infrared optical conductivity of URu2Si2, revealing a partial spectral weight suppression below 30 K linked to bandstructure changes, likely representing a crossover rather than a phase transition.

Contribution

It provides detailed measurements of optical anisotropy and spectral weight suppression in URu2Si2, highlighting a crossover phenomenon without thermodynamic phase transition evidence.

Findings

Spectral weight suppression around 12 meV below 30 K

Anisotropic optical conductivity observed along a- and c-axes

No significant impact on entropy or DC transport properties

Abstract

We performed far-infrared optical spectroscopy measurements on the heavy fermion compound URu 2 Si 2 as a function of temperature. The light's electric-field was applied along the a-axis or the c-axis of the tetragonal structure. We show that in addition to a pronounced anisotropy, the optical conductivity exhibits for both axis a partial suppression of spectral weight around 12 meV and below 30 K. We attribute these observations to a change in the bandstructure below 30 K. However, since these changes have no noticeable impact on the entropy nor on the DC transport properties, we suggest that this is a crossover phenomenon rather than a thermodynamic phase transition.