  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.
