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Tuning gaps and phases of a two-subband system in a quantizing magnetic field

V. M. Apalkov·M. E. Portnoi
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Abstract

In this work we study the properties of a two-subband quasi-two-dimensional electron system in a strong magnetic field when the electron filling factor is equal to four. When the cyclotron energy is close to the intersubband splitting the system can be mapped onto a four-level electron system with an effective filling factor of two. The ground state is either a ferromagnetic state or a spin-singlet state, depending on the values of the inter-level splitting and Zeeman energy. The boundaries between these phases are strongly influenced by the inter-electron interaction. A significant exchange-mediated enhancement of the excitation gap results in the suppression of the electron-phonon interaction. The rate of absorption of non-equilibrium phonons is calculated as a function of Zeeman energy and inter-subband splitting. The phonon absorption rate has two peaks as a function of intersubband splitting and has a step-like structure as a function of Zeeman energy.

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V. M. Apalkov, M. E. Portnoi. 2001-11-20. Tuning gaps and phases of a two-subband system in a quantizing magnetic field. https://doi.org/10.1103/physrevb.65.125310

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