13 research outputs found
Circular-Polarization-Dependent Study of Microwave-Induced Conductivity Oscillations in a Two-Dimensional Electron Gas on Liquid Helium
The polarization dependence of photoconductivity response at
cyclotron-resonance harmonics in a nondegenerate two-dimensional (2D) electron
system formed on the surface of liquid helium is studied using a setup in which
a circular polarization of opposite directions can be produced. Contrary to the
results of similar investigations reported for semiconductor 2D electron
systems, for electrons on liquid helium, a strong dependence of the amplitude
of magnetoconductivity oscillations on the direction of circular polarization
is observed. This observation is in accordance with theoretical models based on
photon-assisted scattering and, therefore, it solves a critical issue in the
dispute over the origin of microwave-induced conductivity oscillations.Comment: 5 pages, 4 figure
Thermoelectric transport in a correlated electron system on the surface of liquid helium
We report on the direct observation of the thermoelectric transport in a
nondegenerate correlated electron system formed on the surface of liquid
helium. We find that the microwave-induced excitation of the vertical
transitions of electrons between the surface-bound states leads to their
lateral flow, which we were able to detect by employing a segmented electrode
configuration. We show that this flow of electrons arises due to the Seebeck
effect, thus our method provides a new tool to study thermoelectricity in a
disorder-free correlated electron system. Our experimental results are in good
agreement with the theoretical calculations based on kinetic equations, with
proper account of fast electron-electron collisions.Comment: 5 pages, 3 figures, supplementary material
Strong coupling of a two-dimensional electron ensemble to a single-mode cavity resonator
We investigate the regime of strong coupling of an ensemble of two-dimensional electrons to a single-mode cavity resonator. In particular, we realize such a regime of light-matter interaction by coupling the cyclotron motion of a collection of electrons on the surface of liquid helium to the microwave field in a semiconfocal Fabry-Pérot resonator. For the corotating component of the microwave field, the strong coupling is pronouncedly manifested by the normal-mode splitting in the spectrum of coupled field-particle motion. We present a complete description of this phenomenon based on classical electrodynamics, as well as show that the full quantum treatment of this problem results in mean-value equations of motion that are equivalent to our classical result. For the counterrotating component of the microwave field, we observe a strong resonance when the microwave frequency is close to both the cyclotron and cavity frequencies. We show that this surprising effect, which is not expected to occur under the rotating-wave approximation, results from the mixing between two polarization components of the microwave field in our cavity
Motional quantum states of surface electrons on liquid helium in a tilted magnetic field
The Jaynes-Cummings model (JCM), one of the paradigms of quantum
electrodynamics, was introduced to describe interaction between light and a
fictitious two-level atom. Recently it was suggested that the JCM Hamiltonian
can be invoked to describe the motional states of electrons trapped on the
surface of liquid helium and subjected to a constant uniform magnetic field
tilted with respect to the surface [Yunusova et al. Phys. Rev. Lett. 122,
176802 (2019)]. In this case, the surface-bound (Rydberg) states of an electron
are coupled to the electron cyclotron motion by the in-plane component of
tilted field. Here we investigate, both theoretically and experimentally, the
spectroscopic properties of surface electrons in a tilted magnetic field and
demonstrate that such a system exhibits a variety of phenomena common to the
light dressed states of atomic and molecular systems. This shows that electrons
on helium realize a prototypical atomic system where interaction between
components can be engineered and controlled by simple means and with high
accuracy, and which therefore can be potentially used as a new flexible
platform for quantum experiments. Our work introduces a pure condensed-matter
system of electrons on helium into the context of atomic, molecular and optical
physics.Comment: 14 pages, 11 figure
The features of the collective modes in aerogels filled with superfluid helium
The velocity of fast and slow collective modes of 90, 94 and 98% porosity aerogels filled with superfluid helium were measured by means of low-frequency resonant technique at temperatures 0.5–2.5 K. The temperature dependences of velocities of both modes are compared with the hydrodynamic theory which was modified taking into account the mobility of the aerogel matrix, porosity of media and tortuosity of an acoustic way. It has been found that the fast and slow modes in an aerogel are coupled much stronger than the first and second sounds in bulk He II