Spin and charge currents driven by the Higgs mode in high-field superconductors

Abstract

The Higgs mode in superconducting materials describes slowly decaying oscillations of the order parameter amplitude. We demonstrate that in superconductors with a built-in spin-splitting field the Higgs mode is strongly coupled to the spin degrees of freedom, allowing for the generation of time-dependent spin currents. Converting such spin currents to electric signals by spin-filtering elements provides a tool for the second-harmonic generation and the electrical detection of the Higgs mode generated by the external irradiation. The nonadiabatic spin torques generated by these spin currents allow for the magnetic detection of the Higgs mode by measuring the precession of the magnetic moment in the adjacent ferromagnet. We discuss also the reciprocal effect, which is the generation of the Higgs mode by the magnetic precession. Coupling the collective modes in superconductors to light and magnetic dynamics provides an opportunity for the study of superconducting optospintronics.

Coupling the Higgs mode and ferromagnetic resonance in spin-split superconductors with Rashba spin-orbit coupling

“…That is why in earlier experiments, the Higgs mode was only observed in charge-density-wave (CDW) coexisting systems [6][7][8][9][10][11]. With the advance of terahertz spectroscopy technique [12] it became possible to investigate the Higgs mode through the nonlinear light-Higgs coupling [13][14][15][16][17][18]. In these experiments, the perturbation of the order parameter is proportional to the square of the external electromagnetic field δ ∝ E 2 , so very strong laser pulses are required.…”

Reducing the frequency of the Higgs mode in a helical superconductor coupled to an LC circuit

“…1. Despite the progress in studying the Higgs mode in systems where charge-density-wave order and superconductivity coexist [5][6][7][8][9], or via its nonlinear coupling to the electromagnetic (EM) field [10][11][12][13][14][15][16][17][18][19][20][21], detecting unequivocally the Higgs mode, in general, remains a challenging task.…”

Dynamics of Two Ferromagnetic Insulators Coupled by Superconducting Spin Current

“…Boundary conditions.-At arbitrary temperatures and with finite spin-orbital or spin-flip scattering times τ so=sf , we determine the SC spin accumulation in the dirty limit from the full Usadel equation [24], using the spin-mixing BC [15,32]…”