Abstract
A resonance-induced change in the resistivity of the surface state electrons (SSE) exposed to the microwave (MW) radiation is observed. The MW frequency corresponds to the transition energy between two lowest Rydberg energy levels. All measurements are done with electrons over liquid 3He in a temperature range 0.45-0.65 K, in which the electron relaxation time and the MW absorption linewidth are determined by collisions with helium vapor atoms. The input MW power is varied by two orders of magnitude, and the resistivity is always found to increase. This effect is attributed to the heating of electrons with the resonance MW radiation. The temperature and the momentum relaxation rate of the hot electrons are calculated as a function of the MW power in the cell, and the Rabi frequency is determined from the comparison of the theoretical result with the experiment. In addition, the broadening of the absorption signal caused by the heating is studied experimentally, and the results are found to be in good agreement with our calculations.
Highlights
It is well known that an electron outside the liquid is attracted to helium surface by a weak image force, while it is prevented to enter the liquid by a strong repulsion due to the Pauli exclusion principle
In conclusion, we observed the resonant increase in the electron resistivity upon irradiation of the surface state electrons (SSE) with resonant MW radiation
This effect is caused by the heating of SSE with the absorbed MW power and is due to the increase of the inter-subband scattering rate of the hot electrons
Summary
It is well known that an electron outside the liquid is attracted to helium surface by a weak image force, while it is prevented to enter the liquid by a strong repulsion due to the Pauli exclusion principle. The SSE are trapped into potential well and their motion in the direction normal to the surface is restricted to the hydrogen-like bound states with energies ǫn = −∆/n2, where n ≥ 1 is an integer number and ∆ is the effective Rydberg energy The latter is about 4 K for electrons over 3He, and at typical experimental conditions T 1 K almost all electrons are in the ground level. Volodin and Edel’man[6] observed the resonant change in the electron conductivity as a result of the interaction with microwaves Both experiments were done with electrons above 4He and 3He and in the temperature range 0.3−0.5 K, which corresponds to ripplon scattering and vapor-atom scattering regimes for 4He and 3He respectively. Some conclusions are drown and the future plans are outlined
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