Spin pumping effect in non-Fermi liquid metals

TL;DR

This paper proposes using the spin pumping effect as a novel probe to detect non-Fermi liquid behaviors at 2D magnetic interfaces, revealing universal scaling laws near quantum critical points.

Contribution

It introduces a theoretical framework connecting spin pumping measurements to NFL behaviors, highlighting universal power-law scalings and the non-quasiparticle nature of spin carriers.

Findings

Power-law scaling of ferromagnetic resonance modulations near QCPs.

Negative power-law exponents in Gilbert damping at the Ising nematic QCP.

Restoration of damping mechanism at finite temperature in quantum critical regime.

Abstract

Spin pumping effect is a sensitive and well-established experimental method in two-dimensional (2D) magnetic materials. We propose that spin pumping effect can be a valuable probe for non-Fermi liquid (NFL) behaviors at the 2D interface of magnetic heterostructures. We show that the modulations of ferromagnetic resonance exhibit power-law scalings in frequency and temperature for NFL metals induced near a quantum critical point (QCP). At the Ising nematic QCP, we demonstrate that the enhanced Gilbert damping coefficient $\delta \alpha$ acquires negative power-law exponents in distinct frequency regimes. The exponents convey universal parameters inherited from the QCP and reflect the non-quasiparticle nature of the spin carriers in the NFL metal. At finite temperature, we show that the Gilbert damping mechanism is restored in the quantum critical regime and $\delta \alpha$ measures the temperature dependence of the correlation length. Our theoretical proposal has the potential to stimulate the development of an interdisciplinary research domain where insights from non-equilibrium spin physics in spintronics are integrated into strongly correlated matter.