Investigation of electrons localized above solid hydrogen by means of the cyclotron resonance method

Abstract

The magnetoresistance and cyclotron resonance of a two-dimensional sheet of electrons localized above liquid and solid hydrogen surfaces are investigated at the frequency of 20 GHz. It is found that the effective electron mass relevant to the motion along the surface is close to the free electron mass. The electron mean free path is determined by collisions with defects of the solid hydrogen surface. For 5≲T≲12 K the electron mobility was ∼8×10⁴/T cm²/V sec, with 20% accuracy, for all the specimens investigated. ForT≲5 K the mobility follows the law$\mu \propto 1/\sqrt {{\text{W}}_{\text{e}} }$, wherew _e is the mean electron energy. The numerical values of the electron mobilities for different specimens differ by factors up to five, and forT≲1 K they fall within within the range 2×10⁴ to 10⁵ cm²/V sec. The experimental results indicate that the solid hydrogen surface has a terrace structure with flat sections about 10⁻⁵ cm in size. During the investigation of electrons localized above a saturated helium film wetting the solid hydrogen, we observed a shift of the resonance to weaker magnetic fields, which amounts to ∼100% at a pressing field of ∼10³ V/cm. It is shown that this shift can be explained by the terrace structure of the substrate.