Denis Konstantinov, M. I. Dykman, M. J. Lea, Yu. P. Monarkha, K. Kono
We study nonlinear inter-subband microwave absorption of electrons bound to
the liquid helium surface. Already for a comparatively low radiation intensity,
resonant absorption due to transitions between the two lowest subbands is
accompanied by electron overheating. The overheating results in a significant
population of higher subbands. The Coulomb interaction between electrons causes
a shift of the resonant frequency, which depends on the population of the
excited states and thus on the electron temperature $T_e$. The latter is
determined experimentally from the electron photoconductivity. The
experimentally established relationship between the frequency shift and $T_e$
is in reasonable agreement with the theory. The dependence of the shift on the
radiation intensity introduces nonlinearity into the rate of the inter-subband
absorption resulting in bistability and hysteresis of the resonant response.
The hysteresis of the response explains the behavior in the regime of frequency
modulation, which we observe for electrons on liquid $^3$He and which was
previously seen for electrons on liquid $^4$He.
View original:
http://arxiv.org/abs/1201.5910
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