arXiv subjects

James Annett

Publications and source records attributed to James Annett.

3 recordsLinked to original sources

arXiv2022

Uniaxial strain, topological band singularities and pairing symmetry changes in superconductors

Uniaxial strain affects pairing symmetry states in superconductors by changing the lattice symmetry, and by altering Fermi surface topology. Here, we present a systematic study of these effects within a one-band negative-U Hubbard model for s, p and d-wave pairing states. We consider a general 2D model that can be applied to superconductors under uniaxial strain, modelled via hopping anisotropy, on a square lattice. The results presented here model an in plane compression along the x-axis, which reduces the lattice symmetry from a tetragonal to an orthorhombic crystal space group. The effects of hopping anisotropy on the different types of gap pairings are explored. We show that changes in Tc are tunable with hopping anisotropy and depend on the orientation of the gap function in relation to the opening of the Fermi surface during the Lifshitz transition. In comparing the model results to experimental data for the case of Sr2RuO4 it is found that both the d + id and d + ig pairings best describe the changes in Tc for the superconducting state in regards to its response to small uniaxial strain.

cond-mat.supr-con↗

arXiv2021

Magnetically-textured superconductivity in elemental Rhenium

Recent $μ$SR measurements revealed remarkable signatures of spontaneous magnetism coexisting with superconductivity in elemental rhenium. Here we provide a quantitative theory that uncovers the nature of the superconducting instability by incorporating every details of the electronic structure together with spin-orbit coupling and multi-orbital physics. We show that conventional $s$-wave superconductivity combined with strong spin-orbit coupling is inducing even-parity odd-orbital spin triplet Cooper pairs, and in presence of a screw axis Cooper pairs' migration between the induced equal-spin triplet component leads to an exotic magnetic state.

cond-mat.supr-con↗

arXiv1996

Experimental Constraints on the Pairing State of the Cuprate Superconductors: an Emerging Consensus

We present a critical discussion of recent experimental probes of the pairing state of the high temperature superconductors, focusing primarily, but not exclusively, on \Yba, where the best data currently exist. Penetration depth measurements near \Tc\ give no indication of an extra transition, indicating that the pairing state is a one-dimensional representation of the crystal symmetry. Penetration depth measurements at low temperatures provide strong evidence for a change in sign of the gap function over the Fermi surface. Quantum mechanical phase interference experiments generally confirm this and in addition show that the nodal positions are consistent with a \dx2y2\ pairing state. This pairing state is consistent with photoemission measurements of the gap function, Raman scattering, the effect on \Tc\ of impurities, and many other data (reviewed by two of us previously) which indicate the presence of low lying excitations in the superconducting state. We also discuss evidence that apparently does not fit in with a \dx2y2\ pairing state, and we describe possible alternative scenarios.

cond-mat↗