Abbreviated Journal Title
Phys. Rev. B
UPPER CRITICAL-FIELD; URHGE; TEMPERATURE; MAGNETISM; UPT3; Physics, Condensed Matter
We employ the Klemm-Clem transformations to map the equations of motion for the Green functions of a clean superconductor with a general ellipsoidal Fermi surface (FS) characterized by the effective masses m(1), m(2), and m(3) in the presence of an arbitrarily directed magnetic induction B = B( sin theta cos phi, sin theta sin phi, cos theta) onto those of a spherical FS. We then obtain the transformed gap equation for a transformed pairing interaction (V) over tilde ((sic), (sic)') appropriate for any orbital order parameter symmetry. We use these results to calculate the upper critical induction B-c2(theta, phi) for an orthorhombic ferromagnetic superconductor with transition temperatures T-Curie > T-c. We assume the FS is split by strong spin-orbit coupling, with a single parallel-spin (up arrow up arrow) pairing interaction of the p-wave polar state form locked onto the (e) over cap3 crystal axis normal to the spontaneous magnetization M-0 perpendicular to < (e)over cape > (3) due to the ferromagnetism. The orbital harmonic oscillator eigenvalues are modified according to B - > B alpha, where alpha(theta, phi) = root m(3)/m root cos(2)theta + gamma(-2)(phi) sin(2)theta, gamma(2)(phi) = m(3)/(m(1) cos(2)phi + m(2) sin(2)phi) and m = (m(1)m(2)m(3))(1/3). At fixed phi the order parameter anisotropy causes B-c2 to exhibit a novel theta dependence, which for gamma(2)(phi) > 3 becomes a double peak at 0 degrees < theta* < 90 degrees and at 180 degrees - theta*, providing a sensitive bulk test of the order parameter orbital symmetry in both phases of URhGe and in similar compounds still to be discovered.
Physical Review B
Lörscher, Christopher; Zhang, Jingchuan; Gu, Qiang; and Klemm, Richard A., "Anomalous angular dependence of the upper critical induction of orthorhombic ferromagnetic superconductors with completely broken p-wave symmetry" (2013). Faculty Bibliography 2010s. 4337.