Percolative nature of the transition from 60 K to 90 K phase in YBa2Cu3O6+d

TL;DR

This study investigates the transition between 60K and 90K phases in YBa2Cu3O6+d, revealing a percolative transition involving superconducting nanoclusters within an insulating matrix, based on heat capacity measurements.

Contribution

It provides evidence that the phase transition is percolative and models the underdoped phase as superconducting nanoclusters embedded in an insulating matrix.

Findings

Doping dependence of heat capacity jump contradicts homogeneous electronic density assumption.

Transition from 60K to 90K phase is percolative in nature.

Underdoped 60K phase consists of superconducting nanoclusters in an insulating matrix.

Abstract

We have measured the heat capacity of YBa2Cu3O6+d for 0.7<d<0.8 between 1.8 and 300K. It was found that doping dependences of specific heat jump and temperature of heat capacity jump contradict to the assumption of spatially homogeneous electronic density. The results suggest that the transition from 60K to 90K phase has a percolative nature and the structure of underdoped 60K phase can be considered as array of superconducting nanoclusters embedded in the insulating matrix.