Revealing Hidden Phase Modulations in Superconductors with Finite-Momentum Pairing

Pair-density waves (PDWs) are superconducting states where Cooper pairs carry finite momenta, leading to spatial modulation of the order parameter. The Larkin–Ovchinnikov (LO) type features an oscillating gap magnitude, while the Fulde–Ferrell (FF) type exhibits a uniform magnitude but an oscillating phase. While LO-type PDWs can be detected by spatial probes of the gap magnitude such as scanning tunneling microscopy, detecting the latter is notoriously difficult, as it requires phase sensitive probes. In this talk, I will propose a Josephson junction set-up that can expose these hidden phase modulations, providing a qualitative signature detecting FF-type PDWs. I will discuss implications for half and quarter-metal superconductivity in rhombohedral graphene.