Thermodynamic properties of underdoped YBa2Cu3O6+x cuprates for several doping values

Abstract

We report the thermodynamic properties of cuprate superconductors YBa2Cu3O[Formula: see text], with [Formula: see text] ranging from underdoped ([Formula: see text]) to optimally doped ([Formula: see text]) regions. We model cuprates as a boson–fermion gas mixture immersed in a layered structure, which is generated via a Dirac-comb potential applied in the perpendicular direction to the CuO2 planes, while the particles move freely in the other two directions. The optimal system parameters, namely, the planes’ impenetrability and the paired-fermion fraction, are obtained by minimizing the Helmholtz free energy in addition to fixing the critical temperature [Formula: see text] to its experimental value. Using this optimized scheme, we calculate the entropy, the Helmholtz free energy and the specific heat as functions of temperature. Additionally, some fundamental properties of the electronic specific heat are obtained, such as the normal linear coefficient [Formula: see text], the quadratic [Formula: see text] term and the jump height at [Formula: see text]. We reproduce the cubic [Formula: see text] term of the total specific heat for low temperatures. Also our multilayer model inherently brings with it the mass anisotropy observed in cuprate superconductors. Furthermore, we establish the doping value beyond which superconductivity is suppressed.