Inhomogeneous high temperature melting and decoupling of charge density waves in spin-triplet superconductor UTe2

Abstract

Periodic spatial modulations of the superfluid density, or pair density waves, have now been widely detected in unconventional superconductors, either as the primary or the secondary states accompanying charge density waves. Understanding how these density waves emerge, or conversely get suppressed by external parameters, provides an important insight into their nature. Here we use spectroscopic imaging scanning tunneling microscopy to study the evolution of density waves in the heavy fermion spin-triplet superconductor UTe2 as a function of temperature and magnetic field. We discover that charge modulations, composed of three different wave vectors gradually weaken but persist to a surprisingly high temperature T_CDW ~ 10-12 K. By tracking the local amplitude of modulations, we find that these modulations become spatially inhomogeneous, and form patches that shrink in size with higher temperature or with applied magnetic field. Interestingly, one of the density wave vectors along the mirror symmetry has a slightly different temperature onset, thus revealing an unexpected decoupling of the three-component CDW state. Importantly, T_CDW determined from our work matches closely to the temperature scale believed to be related to magnetic fluctuations, providing the first possible connection between density waves observed by surface probes and bulk measurements. Combined with magnetic field sensitivity of the modulations, this could point towards an important role of spin fluctuations or short-range magnetic order in the formation of the primary charge density wave.