Excitations in a spin-polarized two-dimensional electron gas

Abstract

A remarkably long-lived spin plasmon may exist in two-dimensional electron liquids with imbalanced spin up and spin down population. Predictions for this interesting mode by Agarwal et al. [Phys. Rev. B 90, 155409 (2014)] are based on the random phase approximation. We here show how to account for spin dependent correlations from known ground state pair correlation functions and study the consequences on the various spin dependent longitudinal response functions. The spin plasmon dispersion relation and its critical wave vector for Landau damping by minority spins turn out to be significantly lower. We further demonstrate that spin dependent effective interactions imply a rich structure in the excitation spectrum of the partially spin-polarized system. Most notably, we find a "magnetic antiresonance", where the imaginary part of both, the spin-spin as well as the density-spin response function vanish. The resulting minimum in the double-differential cross section is awaiting experimental confirmation.

Resonant and anti‐resonant modes of the dilute, spin‐inbalanced, two‐dimensional electron liquid including correlations

“…For sufficient imbalance in the spin population, as realized in typical spintronic 2DELs, this collective mode was proposed be long‐lived due to only weak Landau damping. However, accounting for correlation effects lowers the spin‐plasmon dispersion, implying that it enters the strong damping continuum at much lower wave vectors . Similar situations are known for the acoustic modes in other binary Coulomb systems, such as ionic mixtures, electron bilayers, semiconductor double wells, or the interface 2DEL of perovskites coupled to graphene (the list being far from complete; note also recent work on static many‐body correlations in graphene and the linear mode in the graphene‐related MoS 2 ).…”

Chirality and intrinsic dissipation of spin modes in two-dimensional electron liquids

“…As the spin-wave stiffness S sw contains Coulombic contributions, SOC induces a breaking of the Larmor's theorem (39). Note that, since q = 0, changing the ϕ angle has to be understood as tuning the precession direction of the spins with respect to the crystalline axis.…”

“…(a) The band structure of Bi 2 Se 3 around the Brillouin zone center, reconstructed from ARPES results in Refs [39,40]…”

Shift of the collective mode of polarized graphene on a substrate using spin-sensitive response theory

“…This picture also nicely demonstrates how the plasmon and the optical SiO 2 modes to repel each other due to the coupling between graphene and substrate in Eq. (16). [39] is the prominent curved white region in the rightmost panel; the corresponding dark-blue dash-dotted curve has a distinct gap around ω ≈ 1.5µ, and the green dashed curve becomes zero there.…”

“…Placing such a spin-imbalanced 2DEL between coupled (spin-torque) nano-magnets, would enable to tune their coupling via controlling the spin populations. With the prominent electron layers realized in GaAs-GaAlAs heterostructures this intriguing idea does not work, as correlations lower the spin-plasmon peak [16].…”