The Strange Case of Magnetic Field Sensitive Charge Density Waves in UTe2

Fundamentally new, and unexpected phases may emerge when superconductivity appears in a strongly correlated system. In this work we use scanning tunneling microscopy to study an unusual charge density wave (CDW) order in the heavy fermion triplet superconductor, UTe₂. Our STM data reveal an incommensurate CDW whose intensity gets weaker with increasing field, which eventually disappears at the superconducting critical field, Hc2. To explain the origin and phenomenology of this unusual CDW, we construct a Ginzburg-Landau theory for a uniform triplet superconductor coexisting with three triplet pair density wave (PDW) states which would result in daughter CDW states. An interesting prediction of the theory is that vortices and half-vortices of the superconducting and PDW states would create topological defects in the CDW. By mapping the amplitude and phase of the CDW order in magnetic field, we reveal pairs of topological defects (dislocations of the CDW) with positive and negative phase winding. At the location of each topological defect, the amplitude of the CDW goes to zero, We show that the number of these topological defects increases with magnetic field eventually resulting in the diminishment of the CDW phase. This work reveals the important role of magnetic field generated topological defects in the melting the CDW order parameter in UTe₂ and provides support for the existence of a parent triplet pair density wave order on the surface of UTe₂.

Speaker: Vidya Madhavan, University of Illinois Urbana-Champaign