David G. Rees

Transport Measurements of Strongly Correlated Electrons on Helium in a Classical Point-Contact Device

We present transport measurements of electrons on the surface of liquid helium in a microchannel device in which a constriction may be formed by a split-gate electrode. The surface electron current passing through the microchannel first decreases and is then completely suppressed as the split-gate voltage is swept negative. The current decreases in a steplike manner, due to changes in the number of electrons able to pass simultaneously through the constriction. We investigate the dependence of the electron transport on the AC driving voltage and the DC potentials applied to the sample electrodes, in order to understand the electrostatic potential profile of the constriction region. Our results are in good agreement with a finite element modeling analysis of the device. We demonstrate that the threshold of current flow depends not only on the applied potentials but also on the surface electron density. The detailed understanding of the characteristics of such a device is an important step in the development of mesoscopic experiments with surface electrons on liquid helium.

Reentrant Melting of a Classical Quasi-One-Dimensional Wigner Crystal on the Surface of Liquid Helium

We present transport measurements of electrons on the surface of liquid helium confined to a microscopic channel, the effective width of which can be controlled electrostatically. Above 1 K the electron system is liquid-like and the conductance varies smoothly with the channel width. At lower temperatures the system forms a classical quasi-one-dimensional Wigner crystal (WC). Close to the WC melting temperature, the current oscillates as the channel width is varied, due to reentrant melting as recently reported [H. Ikegami, H. Akimoto, D. G. Rees, and K. Kono: Phys. Rev. Lett. 109 (2012) 236802]. In the WC regime we observe Bragg–Cherenkov ripplon scattering, a signature of strong spatial electron order, for both the widely open channel and the single electron chain.

Structural order and melting of a quasi-one-dimensional electron system

We investigate the influence of confinement on the positional order of a quasi-1D electron system trapped on the surface of liquid helium. We find evidence that the melting of the Wigner solid (WS) depends on the confinement strength, as well as electron density and temperature. A reentrant solid-liquid-solid transition is observed for increasing electron density under constant electrostatic confinement. As the electron row number

Transport of electrons on liquid helium in a microchannel device near the current threshold

{N}_{y}

Point-contact transport properties of strongly correlated electrons on liquid helium.

changes, varying commensurability results in a modulation of the WS order, even when

Commensurability-dependent transport of a Wigner crystal in a nanoconstriction.

{N}_{y}

Evidence for reentrant melting in a quasi-one-dimensional Wigner crystal.

is large (several tens). This is confirmed by Monte Carlo simulations.

Transport of Electrons on Liquid Helium across a Tunable Potential Barrier in a Point Contact-like Geometry

We study the transport of strongly interacting electrons on the surface of liquid helium confined in a microchannel geometry, near the current threshold point. The current threshold depends on the electrostatic confinement, created by the microchannel electrodes, and on the electrostatic potential of electron system. Depending on the geometry of the microchannel, the current pinch-off can occur at the center or move to the edges of the microchannel, as confirmed by Finite Element Model calculations. The confining potential dependence of electron conductivity above the current threshold point is consistent with a classical charge continuum model. However, we find that below the threshold point electron transport is suppressed due to charging energy effects.