Single-Particle Density of States of a Superconductor with a Spatially Varying Gap and Phase Fluctuations

Abstract

Recent experiments have shown that the superconducting energy gap in some cuprates is spatially inhomogeneous. Motivated by these experiments, and using exact diagonalization of a model d-wave Hamiltonian, combined with Monte Carlo simulations of a Ginzburg-Landau free energy functional, we have calculated the single-particle density of states LDOS$(\omega ,r)$ of a model high-T${}_c$ superconductor as a function of temperature. Our calculations include both quenched disorder in the pairing potential and thermal fluctuations in both phase and amplitude of the superconducting gap. Most of our calculations assume two types of superconducting regions: $\alpha$, with a small gap and large superfluid density, and $\beta$, with the opposite. If the $\beta$ regions are randomly embedded in an $\alpha$ host, the LDOS on the $\alpha$ sites still has a sharp coherence peak at $T=0$, but the $\beta$ component does not, in agreement with experiment. An ordered arrangement of $\beta$ regions leads to oscillations in the LDOS as a function of energy. The model leads to a superconducting transition temperature $T_c$ well below the pseudogap temperature $T_{c0}$, and has a spatially varying gap at very low $T$, both consistent with experiments in underdoped Bi2212. Our calculated LDOS$(\omega ,r)$ shows coherence peaks for $T<T_c$, which disappear for $T>T_c$, in agreement with previous work considering phase but not amplitude fluctuations in a homogeneous superconductor. Well above $T_c$, the gap in the LDOS disappears.

37 pages, 12 figures. Accepted by Phys. Rev. B. Scheduled Issue: 01 Nov 2006

References in corpus (4)

• Inhomogeneity Induces Resonance Coherence Peaks in Superconducting BSCCO
• The One-Particle Spectral Function and the Local Density of States in a Phenomenological Mixed-Phase Model for High-Temperature Superconductors
• Interplay of disorder and magnetic field in the superconducting vortex state
• Local Density of States and Angle-Resolved Photoemission Spectral Function of an Inhomogeneous D-wave Superconductor

Cited by in corpus (4)

• s-wave Superconductivity Phase Diagram in the Inhomogeneous Two-Dimensional Attractive Hubbard Model
• Effects of inhomogeneities and thermal fluctuations on the spectral function of a model d-wave superconductor
• Phase Diagram of the Attractive Hubbard Model with Inhomogeneous Interactions
• Model for Vortex Pinning in a Two-Dimensional Inhomogeneous d-wave Superconductor