Relaxation of the Excited Rydberg States of Surface Electrons on Liquid Helium

Abstract

We report the first direct observation of the decay of the excited-state population in electrons trapped on the surface of liquid helium. The relaxation dynamics, which are governed by inelastic scattering processes in the system, are probed by the real-time response of the electrons to a pulsed microwave excitation. Comparison with theoretical calculations allows us to establish the dominant mechanisms of inelastic scattering for different temperatures. The longest measured relaxation time is around 1 μs at the lowest temperature of 135 mK, which is determined by the inelastic scattering due to the spontaneous two-ripplon emission process. Furthermore, the image-charge response shortly after applying microwave radiation reveals interesting population dynamics due to the multisubband structure of the system.

Annular confinement for electrons on liquid helium

“…The confinement of the electron gas at the liquid helium surface is due to the dielectric constant discontinuity at the liquid/vacuum interface [1][2][3]. Experiments on microwave absorption by electrons localized at the liquid helium surface are performed in a parallel capacitor configuration [4,[8][9][10] introducing an electric field that neutralizes the surface electron charge and tunes the transition energies between Rydberg states [4,9]. A cross section of the model system is depicted in Fig.…”

“…Electrons at the vacuum side are bound by the image charges that they induce in the weakly dielectric liquid [1][2][3]. The vertical quantization of electron motion in the Coulomb potential well of the image [2,3] gives rise to Rydberg states of hydrogen-like spectrum [1][2][3][4]. The pristine nature of the substrate allowed for the first observation [5] of the Wigner crystallization in electron gas at a low density [6,7].…”

“…The pristine nature of the substrate allowed for the first observation [5] of the Wigner crystallization in electron gas at a low density [6,7]. For studies of electron states at the surface microwave spectroscopic techniques [2] are developed [8][9][10][11] with recent advances on intersubband absorption [11], excitations of high-energy Rydberg states [4], relaxation times [9], and coupling with the superconducting resonance cavity [12][13][14].…”

Thermoelectric transport in a correlated electron system on the surface of liquid helium

“…The electron temperature is determined by balance between the energy gain due to MW absorption and energy loss due to inelastic collisions of SE with scatterers. The latter is slow, in a time scale 10 −6 -10 −7 s for typical temperatures considered here [23]. This allows overheating of the MW-excited SE to a few degrees Kelvin above the bath temperature T for typical MW powers used in the experiment.…”

Single electrons on solid neon as a solid-state qubit platform

“…While the electron-on-solid-Ne (eNe) system can be considered conceptually as an extension to the historically more studied electronon-liquid-He (eHe) system, it renders much stronger surface rigidity that suppresses decoherence through surface excitations 52,68,69 . Compared with eHe that was proposed as a qubit platform over two decades ago 52,[68][69][70][71][72][73] , eNe embodies a potentially even more fascinating, solid-state qubit platform 56,61,74 .…”