arXiv subjects

Aidan Steineman

Publications and source records attributed to Aidan Steineman.

3 recordsLinked to original sources

arXiv2026

Stimulation of superconductivity in $d$-wave superconductors

We study the stimulation of superconductivity by an external electromagnetic radiation --- the Eliashberg effect --- in a disordered $d$-wave superconductor. We use the self-consistent Keldysh--Nambu quasiclassical formalism augmented by an inelastic relaxation term to compute the static correction to the pairing amplitude by treating elastic scattering within the Born approximation with the full second-order impurity vertex retained. We find that the clean $d$-wave superconductor shows no enhancement at any frequency: without a momentum relaxation channel a spatially uniform drive produces no absorption, only pair breaking. Elastic impurity scattering restores absorption and with it activates response in the Eliashberg channel. We find enhancement of the pairing amplitude which is confined to a bounded window in frequency, disorder strength, inelastic scattering rate and gap magnitude. Both edges of the window scale with the gap but are set by the competition between quasiparticle redistribution, heating and pair breaking rather than by a feature of the spectrum. Furthermore, in contrast to the $s$-wave when the threshold is pinned at $2Δ$, the upper edge is not pinned to the maximum gap and crosses it as the system approaches the critical temperature.

cond-mat.supr-con↗

arXiv2026

Quasiclassical theory of nonlinear response in d-wave superconductors

We use a self-consistent Keldysh--Nambu quasiclassical theory to study two related nonlinear phenomena in clean d-wave superconductors: the photo-induced static correction to the order parameter -- the Eliashberg effect -- and third-harmonic generation. Both follow from a systematic perturbative solution of the out-of-equilibrium Eilenberger equation for the Keldysh propagator. For the steady-state correction to the pairing amplitude we find that at temperatures close to the critical temperature and to leading order in the gap magnitude $Δ$, the photo-induced change of the order parameter is zero at all drive frequencies: in contrast to s-wave superconductors, a clean d-wave superconductor exhibits no Eliashberg enhancement at this order. The gap-enhancing quasiparticle-redistribution channel that drives the effect in the s-wave case is suppressed by an additional power of $Δ$ in the d-wave case. For third-harmonic generation we find that the charge-density-fluctuation (particle--hole) channel significantly dominates the Schmid--Higgs amplitude-mode contribution over a broad frequency range, the two becoming comparable only in a narrow window near the resonance frequency $ω\approx 2\sqrt{2}\,Δ$ if one neglects the diamagnetic part of the current in the normal state. We trace this to the nonequilibrium dynamics of nodal quasiparticles, which must be retained explicitly and which also makes the response sensitive to the orientation of the driving field.

cond-mat.supr-con↗

arXiv2025

Magnetic Field Induced Nonlinear Transport in LaTiO$_3$/SrTiO$_3$ Interfaces

Motivated by the recent experimental measurements of the nonlinear longitudinal resistance of the spin-orbit coupled electron gas in the (111) LaTiO$_3$/SrTiO$_3$ interfaces under external in-plane magnetic field [G. Tuvia \emph{et al.}, Phys. Rev. Lett. 132, 146301 (2024)], we formulate a theory of nonlinear electronic transport based on the analysis of the quantum kinetic equation for the Wigner distribution function. Specifically, we evaluate the magnetic field dependence of the second harmonic of the current density at arbitrary values of the magnetic field. The magnitude of the second harmonic increases linearly with the magnetic field at small fields. Upon further increase of the magnetic field, the second harmonic response reaches its maximum value. We find that the position of the peak and its width strongly depend on the relaxation rate due to disorder. Importantly, we discover that the direction of the nonlinear contribution to the current can be completely reversed when the magnetic field reaches a certain critical value.

cond-mat.str-el↗