Acoustic spin Hall effect in strong spin-orbit metals

Abstract

We report on the observation of the acoustic spin Hall effect that facilitates lattice motion–induced spin current via spin-orbit interaction (SOI). Under excitation of surface acoustic wave (SAW), we find that a spin current flows orthogonal to the SAW propagation in nonmagnetic metals (NMs). The acoustic spin Hall effect manifests itself in a field-dependent acoustic voltage in NM/ferromagnetic metal bilayers. The acoustic voltage takes a maximum when the NM layer thickness is close to its spin diffusion length, vanishes for NM layers with weak SOI, and increases linearly with the SAW frequency. To account for these results, we find that the spin current must scale with the SOI and the time derivative of the lattice displacement. These results, which imply the strong coupling of electron spins with rotating lattices via the SOI, show the potential of lattice dynamics to supply spin current in strong spin-orbit metals.

Observation of elastic spin with chiral meta-sources

“…The experimental observation of elastic spin demonstrates the validity and feasibility of intrinsic spin angular momentum in elasticity, which offers a promising platform for future investigation on integrative spin physics among electron 41 , phonon 42 , photon 4 , and magnon 31 , 32 , 36 , and provides new perspectives and means to the integrative on-chip surface-acoustic-wave devices that have shown the great potential in quantum acoustics 43 , 44 .…”

“…Here, by characterizing the displacement field and SAM on conventional metal plate upon the ultrasonic chiral meta-sources, we report the observation of intrinsic elastic spin and experimental demonstration of its basic properties, including the spin-resolved wave mode and the deterministic spin-momentum locked one-way propagation. The results advance the understanding of elastic spin and broadband spin-dependent properties in general solids, provide people more possibility and flexibility to design the on-chip elastic device 26 – 28 , and pave a way for further revealing new phenomena of chiral elasticity 33 – 35 , spin transfer 36 , and conversion in coupled multi-physical systems 31 , 32 .…”

Relativistic Viscous Hydrodynamics with Angular Momentum

“…Only very recently, there has been a rapidly increasing interest in understanding the implication of angular momentum conservation and developing a corresponding relativistic hydrodynamic theory [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. Such interest is strongly fueled by experimental observations as well as phenomenological studies of spin polarization phenomena in rotating matter, with examples ranging from condensed matter flow systems to subatomic fluids in relativistic nuclear collisions [27][28][29][30][31][32][33][34][35]. See recent reviews in e.g.…”

Helicity current generation by distorted Rashba coupling

“…As a detection of AC spin currents, spin wave resonances have been observed by injecting spin currents into ferromagnetic metals [21,22]. Moreover, AC spin currents have been detected by the rectification effect due to magnetostriction [23]. The spin current produced by the present mechanism may be observed by using these methods.…”

“…The effect of SOI on mechanical spin-current generation has also been studied. Kawada et al applied SAWs to a heavy metal/ferromagnetic metal bilayer under an in-plane magnetic field and investigated the angular dependence of DC voltage on the in-plane magnetic field [23]. They found characteristic magnetic dependence, which was not seen when using weak SOI metal instead of heavy metal , indicating mechanical spin-current generation via intrinsic SOI.…”