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Universal Phenomenology of Charge-Spin Interconversion and Dynamics in Diffusive Systems with Spin-Orbit Coupling
Tim Kokkeler1,2, F Sebastian Bergeret1,3, I V Tokatly1,4,5
1Donostia International Physics Center (DIPC), 20018 Donostia-San Sebastián, Spain.
Physical Review Letters
|March 25, 2025
Summary
This study unifies the description of charge transport in normal and superconducting metals with spin-orbit coupling (SOC). It introduces a quantum kinetic theory applicable across all temperatures, capturing key transport phenomena and superconducting fluctuations.
Area of Science:
- Condensed Matter Physics
- Quantum Transport Theory
Background:
- Spin-orbit coupling (SOC) significantly influences electron behavior in metals.
- Understanding transport phenomena in both normal and superconducting states requires a unified theoretical framework.
Purpose of the Study:
- To develop a unified quantum kinetic theory for transport in metals with generic spin-orbit coupling.
- To describe diffusive transport in normal metals and superconductors across the entire temperature range.
- To incorporate superconducting fluctuations and effects of crystal symmetry.
Main Methods:
- Utilizing fundamental constraints: charge conjugation symmetry, causality, and crystal symmetry.
- Employing the Keldysh nonlinear sigma model (NLSM) in the diffusive regime.
- Deriving a quantum kinetic Usadel-type equation from the NLSM saddle point.
Main Results:
- A unified description of transport in normal and superconducting metals with SOC.
- The derived Usadel-type equation captures main transport features and superconducting fluctuations.
- Application yields quantum transport equations including spin Hall, spin current swapping, and spin-galvanic effects.
Conclusions:
- The phenomenological approach is broadly applicable, extending Ginzburg-Landau theory.
- The framework can be extended to systems with broken time-reversal symmetry and hybrid interfaces.
- Enhanced spin-charge interconversion is possible at interfaces with strong SOC.
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