Spin–orbit effects and superconductivity in oxide materials

Abstract

In a variety of materials superconductivity is associated with the existence of a quantum critical point (QCP). In the case of the hole doped cuprates there is evidence which suggests that the important quantum degrees of freedom near the superconducting critical point are localized charge and spin density fluctuations. We argue that if these degrees of freedom are strongly coupled by spin–orbit interactions, a new type of quantum criticality arises with monopole-like quasi-particles as the important quantum degrees of freedom. In layered material this type of quantum criticality can be modeled using a 2-dimensional non-linear Schrodinger equation with an SU(N) gauge field. We exhibit a pairing wave function for quasi-particles that has topological order and anisotropic properties. The superconducting transition would in some respects resemble a KT transition.

Acknowledgements

The author would like to thank Andre Bernevig, Gil Lonzarich, Montu Saxena, Christos Panagopoulos, and Jim Smith for helpful conversations. This work was performed in part under the auspices of the US Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.