Magnetic field effects on the density of states of orthorhombic superconductors

TL;DR

This paper investigates how an in-plane magnetic field influences the quasiparticle density of states in orthorhombic d-wave superconductors, highlighting the effects of crystal symmetry and impurity scattering.

Contribution

It extends the understanding of magnetic field effects on the density of states to orthorhombic superconductors, considering impurity scattering.

Findings

Density of states depends on magnetic field orientation.

Orthorhombic symmetry causes a two-fold pattern in density of states.

Impurity scattering modifies the density of states behavior.

Abstract

The quasiparticle density of states in a two-dimensional d-wave superconductor depends on the orientation of the in-plane external magnetic field H. This is because. in the region of the gap nodes, the Doppler shift due to the circulating supercurrents around a vortex depend on the direction of H. For a tetragonal system the induced pattern is four-fold symmetric and, at zero energy, the density of states exhibits minima along the node directions. But YBa_2C_3O_{6.95} is orthorhombic because of the chains and the pattern becomes two-fold symmetric with the position of the minima occuring when H is oriented along the Fermi velocity at a node on the Fermi surface. The effect of impurity scattering in the Born and unitary limit is discussed.