Normal state specific heat in the cuprates La$_{2-x}$Sr$_x$CuO$_4$ and Bi$_{2+y}$Sr$_{2-x-y}$La$_x$CuO$_{6+δ}$ near the critical point of the pseudogap phase

C. Girod; D. LeBoeuf; A. Demuer; G. Seyfarth; S. Imajo; K. Kindo; Y. Kohama; M. Lizaire; A. Legros; A. Gourgout; H. Takagi; T. Kurosawa; M. Oda; N. Momono; J. Chang; S. Ono; G. -q. Zheng; C. Marcenat; L. Taillefer; T. Klein

doi:10.1103/PhysRevB.103.214506

paper

Normal state specific heat in the cuprates La $_{2 - x}$ Sr $_{x}$ CuO $_{4}$ and Bi $_{2 + y}$ Sr $_{2 - x - y}$ La $_{x}$ CuO $_{6 + δ}$ near the critical point of the pseudogap phase

arXiv:2101.09221 · doi:10.1103/PhysRevB.103.214506

Abstract

The specific heat $C$ of the cuprate superconductors La $_{2 - x}$ Sr $_{x}$ CuO $_{4}$ and Bi $_{2 + y}$ Sr $_{2 - x - y}$ La $_{x}$ CuO $_{6 + δ}$ was measured at low temperature (down to $0.5 K$ ), for dopings $p$ close to $p^{⋆}$ , the critical doping for the onset of the pseudogap phase. A magnetic field up to $35 T$ was applied to suppress superconductivity, giving direct access to the normal state at low temperature, and enabling a determination of $C_{e}$ , the electronic contribution to the normal-state specific heat, at $T \to 0$ . In La $_{2 - x}$ Sr $_{x}$ CuO $_{4}$ at $x = p = 0.22$ , $0.24$ and $0.25$ , $C_{e} / T = 15 - 16 mJmol^{- 1} K^{- 2}$ at $T = 2 K$ , values that are twice as large as those measured at higher doping ( $p > 0.3$ ) and lower doping ( $p < 0.15$ ). This confirms the presence of a broad peak in the doping dependence of $C_{e}$ at $p^{⋆} ≃ 0.19$ , as previously reported for samples in which superconductivity was destroyed by Zn impurities. Moreover, at those three dopings, we find a logarithmic growth as $T \to 0$ , such that $C_{e} / T \sim B ln (T_{0} / T)$ . The peak vs $p$ and the logarithmic dependence vs $T$ are the two typical thermodynamic signatures of quantum criticality. In the very different cuprate Bi $_{2 + y}$ Sr $_{2 - x - y}$ La $_{x}$ CuO $_{6 + δ}$ , we again find that $C_{e} / T \sim B ln (T_{0} / T$ ) at $p ≃ p^{⋆}$ , strong evidence that this $ln (1/ T)$ dependence - first discovered in the cuprates La $_{1.8 - x}$ Eu $_{0.2}$ Sr $_{x}$ CuO $_{4}$ and La $_{1.6 - x}$ Nd $_{0.4}$ Sr $_{x}$ CuO $_{4}$ - is a universal property of the pseudogap critical point. All four materials display similar values of the $B$ coefficient, indicating that they all belong to the same universality class.

8 pages, 6 figures

Normal state specific heat in the cuprates La $_{2 - x}$ Sr $_{x}$ CuO $_{4}$ and Bi $_{2 + y}$ Sr $_{2 - x - y}$ La $_{x}$ CuO $_{6 + δ}$ near the critical point of the pseudogap phase

Abstract

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Normal state specific heat in the cuprates La2−x​Srx​CuO4​ and Bi2+y​Sr2−x−y​Lax​CuO6+δ​ near the critical point of the pseudogap phase

Abstract

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Cited by in corpus (25)

Normal state specific heat in the cuprates La $_{2 - x}$ Sr $_{x}$ CuO $_{4}$ and Bi $_{2 + y}$ Sr $_{2 - x - y}$ La $_{x}$ CuO $_{6 + δ}$ near the critical point of the pseudogap phase