Absence of bulk charge density wave order in the normal state of UTe2

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 UTe₂ 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.

Surface-sensitive scanning tunneling microscopy (STM) has previously found a charge density wave (CDW) up to 10 K in the normal state of the heavy-fermion superconductor UTe₂. Here, using resonant elastic X-ray scattering (REXS) above the superconducting transition, the authors find no evidence for a bulk CDW, suggesting the normal state CDW observed by STM is a surface effect.