Specific heat of underdoped cuprate superconductors from a phenomenological layered Boson–Fermion model

Abstract

We adapt the Boson-Fermion superconductivity model to include layered systems such as underdoped cuprate superconductors. These systems are represented by an infinite layered structure containing a mixture of paired and unpaired fermions. The former, which stand for the superconducting carriers, are considered as noninteracting zero spin composite-bosons with a linear energymomentum dispersion relation in the CuO2 planes where superconduction is predominant, coexisting with the unpaired fermions in a pattern of stacked slabs. The inter-slab, penetrable, infinite planes are generated by a Dirac comb potential, while paired and unpaired electrons (or holes) are free to move parallel to the planes. Composite-bosons condense at a critical temperature at which they exhibit a jump in their specific heat. These two values are assumed to be equal to the superconducting critical temperature Tc and the specific heat jump reported for YBa2Cu3O6.80 to fix our model parameters namely, the plane impenetrability and the fraction of superconducting charge carriers. We then calculate the isochoric and isobaric electronic specific heats for temperatures lower than Tc of both, the composite-bosons and the unpaired fermions, which matches recent experimental curves. From the latter, we extract the linear coefficient (γn) at Tc, as well as the quadratic (αT 2 ) term for low temperatures. We also calculate the lattice specific heat from the ARPES phonon spectrum, and add it to the electronic part, reproducing the experimental total specific heat at and below Tc within a 5% error range, from which the cubic (ßT 3 ) term for low temperatures is obtained. In addition, we show that this model reproduces the cuprates mass anisotropies.

Spin gauge theory, duality and fermion pairing

“…As we will see below, the nonlocal interaction appears naturally if we consider Abrikosov-Nielsen-Olesen (ANO) vortex strings in the Abelian Higgs model interacting with charged fermions. Such a system, called a bosonfermion model, was originally proposed as a model of high-T c superconductivity [11][12][13][14][15][16][17][18][19][20][21], but also appear in models of superconductor-insulator transitions [22][23][24], of BCS-BEC crossover [25,26], and of charged Bose liquids [27]. The system we consider has certain differences with the boson-fermion model, in particular we do not consider the φ ψψ Yukawa interaction of the fermions with the scalar Higgs field.…”

Spin gauge theory, duality and fermion pairing

“…As we will see below, the nonlocal interaction appears naturally if we consider Abrikosov-Nielsen-Olesen (ANO) vortex strings in the Abelian Higgs model interacting with charged fermions. Such a system, called a boson-fermion model, was originally proposed as a model of high-T c superconductivity [15][16][17][18][19][20][21][22][23], but also appear in models of superconductor-insulator transitions [24][25][26], of BCS-BEC crossover [27,28], and of charged Bose liquids [29]. The system we consider has certain differences with the bosonfermion model, in particular we do not consider the φ ψψ Yukawa interaction of the fermions with the scalar Higgs field.…”

Thermal fluctuation conductivity and dimensionality in iron-based superconductors

“…Both phenomenologic and microscopic multi-band theories have been developed to describe the experimental observation of the multi-band electronic structure in most of the iron pnictides families, such as (1111), (11), (111), and (122) families. [20][21][22] However, the single-band model can be used approximately near T c . [23] We use the single-band LD model in this paper to study the fluctuation conductivity of vortex liquid near T c .…”