Experimental observation of a possible first-order phase transition below the superconducting transition temperature in the multilayer cuprate superconductor HgBa2Ca4Cu5Oy

Abstract

A hysteretic specific heat jump at approximately 41K is found experimentally in the multilayer cuprate superconductor HgBa2Ca4Cu5Oy (Hg-1245), with a superconducting transition temperature of 108 K, under a zero magnetic field. This hysteresis suggests the occurrence of a first-order phase transition. We speculate that this phase transition is related to the dynamics of a multicomponent superconducting order parameter originating from five CuO2 planes in a unit cell of Hg-1245.