Calorimetric evidence for two phase transitions in Ba${}_{1-\mathrm{x}}$K${}_{\mathrm{x}}$Fe${}_2$As${}_2$ with fermion pairing and quadrupling states

Ilya Shipulin, Nadia Stegani, Ilaria Maccari +9

Theoretically, materials that break multiple symmetries allow, under certain conditions, the formation of four-fermion condensates above the superconducting critical temperature. S…