Phenomenology of Spin-Triplet Pair-Density Waves, and Applications to UTe2

Recently, experiments have indicated that the heavy fermion superconductor UTe2 hosts PDWs with spin-triplet pairing. In this talk, we will discuss the phenomenology of spin-triplet PDWs and how they are similar and different from the more well studied spin-singlet PDWs. Like spin-singlet PDWs, much of the interesting phenomenology of spin-triplet PDWs arises from their ability to produce daughter order, namely spin-density waves and charge-density waves. These daughter orders inherit unusual sensitivities to external magnetic fields from the parent PDW state. Notably, the daughter CDW couples to both the magnitude and direction of an applied magnetic field, unlike the daughter CDW of a spin-singlet PDW, which only couples to the magnitude. A strong magnetic field will also induce topological defects (i.e. dislocations) in the CDW. Scanning tunneling microscopy studies of UTe2 have found CDWs with these unusual features, providing strong evidence of a spin-triplet PDW. In addition, we will discuss the possibility that spin-triplet PDWs are topological with Majorana zero modes, and relevant experimental signatures.