Magnetoplasma excitations of two-dimensional anisotropic heavy fermions in AlAs quantum wells

V. M. Muravev, A. R. Khisameeva, V. N. Belyanin, I. V. Kukushkin, L. Tiemann, C. Reichl, W. Dietsche, and W. Wegscheider. Phys. Rev. B 92, 041303(R) (2015).

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The spectra of plasma and magnetoplasma excitations in a two-dimensional system of anisotropic heavy fermions are investigated. The spectrum of microwave absorption by disklike samples of stressed AlAs quantum wells at low electron densities shows two plasma resonances separated by a frequency gap. These two plasma resonances correspond to electron mass principle values of (1.10±0.05)m0 and (0.20±0.01)m0. The observed results correspond to the case of a single valley strongly anisotropic Fermi surface. It is established that an increase in electron density results in the population of the second valley, manifesting itself as a drastic modification of the plasma spectrum. We directly determine the electron densities in each valley and the intervalley splitting energy from the ratio of the two plasma frequencies.

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