First Study of Intersubband Absorption in Electrons on Helium under Quantizing Magnetic Fields

TL;DR

This study investigates how perpendicular magnetic fields affect microwave inter-subband absorption in electrons on liquid helium, revealing complex behaviors due to electron decay rate variations and scattering mechanisms.

Contribution

First experimental measurement of inter-subband microwave absorption in electrons on helium under quantizing magnetic fields, highlighting decay rate effects and absorption suppression phenomena.

Findings

Absorption varies intermittently with magnetic field strength.

Decay rates influence absorption intensity and overheating.

Absorption is strongly suppressed at specific magnetic fields.

Abstract

We present the first measurements of inter-subband absorption of microwaves in surface electrons on liquid helium subjected to perpendicular magnetic field B. In quantizing B, the power absorption shows intermittent regions of enhanced and suppressed absorption. This behavior is caused by strong variation of the excited-electron decay rate with B. Particularly, fast decay due to elastic scattering provides condition for strong absorption and overheating of the electron system, while slow decay due to inelastic scattering limits absorption and causes its saturation. An unexpected feature is the strong suppression of absorption at magnetic fields where the inter-subband energy splitting is a multiple number of the cyclotron energy.