“Spin generation from heat and light in metals”

Dr. Gyung Min Choi
Department of Energy Science, Sungkyunkwan University

Dec. 7 (Fri.), 02:30 PM
E6-2. 1st fl. #1323

Abstract:
Manipulating magnetization by a spin current rather than a magnetic field is a fundamental issue in spintronics. Conventionally, spin currents have been generated from charge currents by spin filter effect or spin Hall effect. In this seminar, I will show that spin currents can be generated from heat currents or light injection in metallic systems. Heat transport from electrons to magnons of ferromagnetic metals during ultrafast demagnetization generates a spin density on electrons by angular momentum conservation of electron-magnon scattering [1]. Heat transport from ferromagnetic metals to non-magnetic metals generates spin density at the interface between ferromagnets and non-magnets by spin-dependent Seebeck effect [2]. Density of circularly polarized light inside ferromagnetic metals produces an optomagnetic field by inverse Faraday effect [3]. Absorption of circularly polarized light in non-magnetic heavy metals generates a spin current by longitudinal photo-spin-galvanic effect [4]. These results demonstrate novel mechanisms for the heat-to-spin and light-to-spin conversion in metals.

References
1. G.-M. Choi, B.-C. Min, K.-J. Lee, D. G. Cahill, Spin current generated by thermally driven ultrafast demagnetization, Nature Commun. 5, 4334 (2014).
2. G.-M. Choi, C.-H. Moon, B.-C. Min, K.-J. Lee, D. G. Cahill, Thermal spin-transfer torque driven by the spin-dependent Seebeck effect in metallic spin-valves, Nature Phys. 11, 576 (2015).
3. G.-M. Choi, A. Schleife, and D. G. Cahill, Optical-helicity-driven magnetization dynamics in metallic ferromagnets, Nature Commun. 8, 15085 (2017).
4. G.-M. Choi, O.-S. Jung, D.-G. Lee, S.-W. Lee, K. W. Kim, M. Lim, B.-C. Min, K.-J. Lee, and H.-W. Lee, Optical spin-orbit torque induced by longitudinal photo-spin-current, submitted.