How ‘pairons’ are revealed in the electronic specific heat of cuprates

• Published in: Solid state communications 2021-01, Vol.323, p.114109, Article 114109
• Main Authors: Noat, Yves, Mauger, Alain, Nohara, Minoru, Eisaki, Hiroshi, Sacks, William
• Format: Article
• Language: English
• Subjects: Cuprates superconductors; Electronic specific heat; High-temperature superconductors; Physics; Pseudogap
• ISSN: 0038-1098; 1879-2766
• DOI: 10.1016/j.ssc.2020.114109

Understanding the thermodynamic properties of high-Tc 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 Tc. 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 Tc. 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. •We give a compact formulation of the entropy of cuprates superconductors based on pairon excitations.•The model captures the essential features of the entropy and specific heat as seen in experiments.•The agreement with measurements confirm the formation of pairons, bound pairs in their antiferromagnetic local environment.•Pre-formed pairs existing below T* explain the unconventional behavior of the entropy with respect to the normal state.•The entropy is determined by both pair excitations following Bose-Einstein statistics, and quasiparticle excitations.