TRIDENT Case Card: PHYS-CAV — Cavity-Altered Superconductivity

A TRIDENT diagnostic case card evaluating the experimental demonstration that superconducting behaviour in κ-(BEDT-TTF)₂Cu[N(CN)₂]Br (κ-ET) is modified by coupling to hexagonal boron nitride (hBN) acting as a built-in infrared photonic cavity (Keren et al., Nature 650, 864–868, 2026; doi:10.1038/s41586-025-10062-6). The cavity's hyperbolic phonon-polariton modes resonate with the infrared-active C=C stretching vibration of κ-ET implicated in superconducting pairing, producing a cavity-mediated alteration of the electron–phonon coupling without external light, pressure, or magnetic fields. Gate assessment under USDOP v1.2: G1 PASS, G2 PARTIAL, G3 PARTIAL, G4 CONDITIONAL PASS. This node introduces a third boundary regime to the corpus — electromagnetic boundary control — distinct from geometric boundary restructuring (moiré analogue) and control-scheduler architecture (SHRF qubits). It does not generalise to other superconducting families and does not affect the PHYS-HTSC node (OPEN). Keywords cavity quantum materials · superconductivity · phonon polaritons · hexagonal boron nitride · electron-phonon coupling · TRIDENT · USDOP · case card · boundary condition · electromagnetic environment · κ-ET · molecular superconductor