Cavity engineering reshapes superconductivity at a buried interface
Researchers build a resonant hyperbolic cavity by placing hexagonal boron nitride on the molecular superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br and observe a resonant coupling between hBN’s hyperbolic modes and the C=C stretching mode linked to superconductivity, causing a strong, spatially selective suppression of the local superfluid density at the hBN/κ-ET interface (about 50% in several devices) at 2 K. Non‑resonant controls (RuCl3/κ-ET and hBN/BSCCO) show little or no effect, indicating the suppression is tied to the resonant cavity. The work demonstrates a ground-state modification via dark cavity engineering and suggests a general approach to tailoring electronic phases without external driving.