Ballistic-to-hydrodynamic transition and collective modes for two-dimensional electron systems in magnetic field

Article

关键词: OSCILLATIONS;    RESISTANCE;    TRANSPORT;    GRAPHENE;    PLASMON;    WAVES;   

DOI  :  10.1103/PhysRevB.106.115415

来源: SCIE

【 摘 要 】

The recent demonstrations of viscous hydrodynamic electron flow in two-dimensional electron systems poses serious questions to the validity of existing transport theories, including the ballistic model, the collision-induced and collisionless hydrodynamics. While the theories of transport at hydrodynamic-to-ballistic crossover for free 2D electrons are well established, the same is not true for electrons in magnetic fields. In this paper, we develop an analytically solvable model describing the transition from ballistic to hydrodynamic transport with changing the strength of electron-electron collisions in magnetic fields. Within this model, we find an expression for the high-frequency nonlocal conductivity tensor of 2D electrons. It is valid at arbitrary relation between frequency of external field omega, the cyclotron frequency omega(c), and the frequency of e-e collisions tau(-1)(ee) . We use the obtained expression to study the transformation of 2d magnetoplasmon modes at hydrodynamic-to-ballistic crossover. In the true hydrodynamic regime, omega tau(ee) << 1, the 2DES supports a single magnetoplasmon mode that is not split at cyclotron harmonics. In the true ballistic regime, omega tau(ee) >> 1, the plasmon dispersion develops splittings at cyclotron harmonics, forming the Bernstein modes. A formal long-wavelength expansion of kinetic equations ( collisionless hydrodynamics ) predicts the first splitting of plasmon dispersion at omega asymptotic to 2 omega(c). Still, such expansion fails to predict the zero and negative group velocity sections of true magnetoplasmon dispersion, for which the full kinetic model is required.

【 授权许可】

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