Thermodynamic Properties in Triangular-Lattice Superconductors

Abstract

The study of superconductivity arising from doping a Mott insulator has become a central issue in the area of superconductivity. Within the framework of the kinetic-energy-driven superconducting mechanism, we discuss the thermodynamic properties in triangular-lattice superconductors. It is shown that a sharp peak in the specific-heat appears at the superconducting transition temperature Tc, and then the specific-heat varies exponentially as a function of temperature for the temperatures T < Tc due to the absence of the d-wave gap nodes at the charge-carrier Fermi surface. In particular, the upper critical field follows qualitatively the Bardeen-Cooper-Schrieffer type temperature dependence, and has the same dome-shaped doping dependence as Tc. PACS numbers: 74.25.Bt, 74.20.Mn, 74.62.Dh, arXiv:1511.00842v2 [cond-mat.supr-con]

Asymmetric doping dependence of superconductivity between hole- and electron-doped triangular-lattice superconductors

“…In particular, within this kinetic-energy driven SC mechanism, superconductivity in the electron-doped Mott insulator on a triangular lattice has been discussed based on the t-J model in the fermion-spin representation 29,30 , where the obtained optimal T c occurs in a narrow range of the optimal doping, and then decreases for both underdoped and overdoped regimes, in qualitative agreement with the corresponding experimental result 8 of the electron-doping triangular-lattice cobaltate superconductors Na x CoO 2 •yH 2 O. Moreover, based on this theoretical framework 29,30 , the electromagnetic response 30 , the thermodynamic properties 31 , and the nature of the electron Fermi surface of the electron-doped Mott insulator on a triangular lattice 32 have been discussed, and then the experimental results of the superfluid density, the specific-heat, and the doping dependence of the electron Fermi surface in the triangular-lattice cobaltate superconductors are qualitatively reproduced. Following these previous discussions 29,30 , the full charge-carrier diagonal and off-diagonal Green's functions of the t-t ′ -J model on a triangular-lattice (2) in the SC-state can be obtained as,…”