Long-lived spin plasmons in a spin-polarized two-dimensional electron gas

Abstract

Collective charge-density modes (plasmons) of the clean two-dimensional unpolarized electron gas are stable, for momentum conservation prevents them from decaying into single-particle excitations. Collective spin-density modes (spin plasmons) possess no similar protection and rapidly decay by production of electron-hole pairs. Nevertheless, if the electron gas has a sufficiently high degree of spin polarization ($P>1/7$, where $P$ is the ratio of the equilibrium spin density and the total electron density, for a parabolic single-particle spectrum) we find that a long-lived spin-plasmon---a collective mode in which the densities of up and down spins oscillate with opposite phases---can exist within a "pseudo gap" of the single-particle excitation spectrum. The ensuing collectivization of the spin excitation spectrum is quite remarkable and should be directly visible in Raman scattering experiments. The predicted mode could dramatically improve the efficiency of coupling between spin-wave-generating devices, such as spin-torque oscillators.

8 pages, 4 figures, final published version

References in corpus (3)

• Current induced electron spin polarization in strained semiconductors
• Spin polarized two-dimensional electron gas embedded in semimagnetic quantum well : ground state, spin responses, spin excitations, Raman spectrum
• Optical and electrical spin injection and spin transport in hybrid Fe/GaAs devices

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• Plasmons in spin polarized graphene: a new way to measure spin polarization
• Kinetic analysis of spin current contribution to spectrum of electromagnetic waves in spin-1/2 plasma, Part II: Dispersion dependencies
• Multi-component plasmons in monolayer MoS${}_2$ with circularly polarized optical pumping
• Phenomenological plasmon broadening and relation to the dispersion
• Collective plasmonic modes in the chiral multifold fermionic material CoSi
• Dynamic correlations in the highly dilute 2D electron liquid: loss function, critical wave vector and analytic plasmon dispersion