Absence of bulk charge density wave order in the normal state of UTe$_2$

TL;DR

This study investigates whether bulk charge density wave order exists in UTe$_2$ above its superconducting transition, finding no evidence of such order in the bulk through resonant elastic X-ray scattering, thus questioning previous surface-based observations.

Contribution

The paper provides the first systematic bulk search for charge order in UTe$_2$ above $T_c$, challenging prior surface-based STM findings and exploring implications for the nature of the PDW state.

Findings

No bulk charge order detected above $T_c$ in UTe$_2$

Results suggest charge modulations may be surface-restricted

Implications for the relationship between charge order and superconductivity

Abstract

A spatially modulated superconducting state, known as pair density wave (PDW), is a tantalizing state of matter with unique properties. Recent scanning tunneling microscopy (STM) studies revealed that spin-triplet superconductor UTe$_2$ hosts an unprecedented spin-triplet, multi-component PDW whose three wavevectors are indistinguishable from a preceding charge-density wave (CDW) order that survives to temperatures well above the superconducting critical temperature, $T_{c}$. Whether the PDW is the mother or a subordinate order remains unsettled. Here, based on a systematic search for bulk charge order above $T_{c}$ using resonant elastic X-ray scattering (REXS), we show that the structure factor of charge order previously identified by STM is absent in the bulk within the sensitivity of REXS. Our results invite two scenarios: either the density-wave orders condense simultaneously at $T_{c}$ in the bulk, in which case PDW order is likely the mother phase, or the charge modulations are restricted to the surface.