Electrical transport near quantum criticality in low-dimensional organic superconductors

Abstract

We propose a theory of longitudinal resistivity in the normal phase of quasi-one-dimensional organic superconductors near their quantum critical point where antiferromagnetism borders with superconductivity under pressure. The linearized semiclassical Boltzmann equation is solved numerically, fed in by the half-filling electronic umklapp scattering vertex as derived from one-loop renormalization-group calculations for the quasi-one-dimensional electron-gas model. The momentum and temperature dependence of umklapp scattering has an important impact on spin fluctuations and on the behavior of longitudinal resistivity in the the normal phase. Resistivity is found to be linear in temperature around the quantum critical point at which spin-density-wave order joins superconductivity along the antinesting axis, to gradually evolve towards the Fermi-liquid behavior in the limit of weak superconductivity. A critical analysis of the predictions is made from a comparison with experiments performed on the (TMTSF)2PF6 member of the Bechgaard salt series under pressure. Fair agreement between theory and experiment is then found in the low-temperature range linked to quantum criticality while deviations from predictions become apparent at high temperature.

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