Fig. 4: Emergent anisotropy in the FFLO state.
From: Emergent anisotropy in the Fulde–Ferrell–Larkin–Ovchinnikov state
a, b Δv/v at 1.6 K for u | |b (blue) and u | |c (red) in magnetic fields a parallel (θ = 0°) and b perpendicular (θ = 90°) to the 2D conducting plane. Direction dependence of the longitudinal sound wave propagation is observed only in the FFLO state (green area), whereas the direction dependence of Δv/v in the BCS state and the normal state is not significant. The inset schematics show the electronic states (red: superconductivity, blue: normal state), directions of applied fields (light green arrows), and sound polarization vectors (striped arrows).
