In-plane conductivity of a layered large-bipolaron liquid

TL;DR

This paper explains the normal-state electrical properties of cuprate superconductors by modeling their charge carriers as a large-bipolaron liquid, revealing how weak phonon scattering influences conductivity and resistivity.

Contribution

It introduces a large-bipolaron liquid model that accounts for the weak phonon scattering and explains the temperature dependence of resistivity and conductivity in cuprates.

Findings

Resistivity remains nearly proportional to temperature below the Debye temperature.

High-frequency conductivity is dominated by electronic excitations and photo-ionization.

The large-bipolaron liquid exhibits moderate mobility despite large effective mass.

Abstract

Distinctive normal-state properties of cuprate superconductors follow from their charge carriers forming a large-bipolaron liquid. The very weak scattering of the slow-moving heavy-massed excitations of the liquid by acoustic phonons yields a scattering rate that is less than the Debye frequency. The moderate liquid mobility, greater than 1 cm2/V-sec at 300 K, results as the weak scattering of the liquid compensates for its large mass. In resolution of a long-standing dilemma, the dc resistivity resulting from scattering by acoustic phonons remains nearly proportional to temperature to well below the Debye temperature. Above the Debye frequency the frequency-dependent conductivity is dominated by excitation and photo-ionization of the self-trapped electronic carriers of the large-bipolarons. Below the Debye frequency the frequency-dependent conductivity is dominated by the Drude-like collective motion of the large-bipolaron liquid. The gap between these two domains sharpens with decreasing temperature as phonon scattering of the liquid diminishes. The high-frequency electronic excitations survive in the superconducting state.