How 'pairons' are revealed in the electronic specific heat of cuprates

TL;DR

This paper demonstrates that the pairon model explains the unconventional electronic specific heat and entropy in cuprate superconductors, linking the pseudogap to superconductivity and revealing doping-dependent excitations.

Contribution

It shows that the pairon concept accounts for the specific heat and entropy features across the phase diagram, unifying pseudogap and superconducting states.

Findings

Pairon excitations dominate in underdoped cuprates.

Coexistence of bosonic and fermionic excitations with doping.

Model explains the doping-dependent specific heat features.

Abstract

Understanding the thermodynamic properties of high-$T_c$ cuprate superconductors is a key step to establish a satisfactory theory of these materials. The electronic specific heat is highly unconventional, distinctly non-BCS, with remarkable doping-dependent features extending well beyond $T_c$. The pairon concept, bound holes in their local antiferromagnetic environment, has successfully described the tunneling and photoemission spectra. In this article, we show that the model explains the distinctive features of the entropy and specific heat throughout the temperature-doping phase diagram. Their interpretation connects unambiguously the pseudogap, existing up to $T^*$, to the superconducting state below $T_c$. In the underdoped case, the specific heat is dominated by pairon excitations, following Bose statistics, while with increasing doping, both bosonic excitations and fermionic quasiparticles coexist.