Wigner Solid on the Free Surface of SuperfluidH3e

Abstract

We report the measurement of electrical transport of the two-dimensional Wigner solid (WS) formed on the free surface of superfluid 3 He-B down to 230 mK. The resistance R͑T ͒ dramatically decreases as temperature T decreases, obeying Arrhenius' law, R͑T͒~exp͓2D͑T͒͞k B T͔, with D͑T ͒ which we assign to the superfluid energy gap. That is, the scattering of 3 He quasiparticles by the WS determines the transport. The resistance depends systematically on the static electric field which presses the WS toward the liquid surface. We propose that the WS acts as a powerful probe for the study of the superfluid 3 He. [S0031-9007 (97)04553-5] PACS numbers: 67.57.Np, 73.20. -r

Neutron reflection from a liquid helium surface

“…The existence of the quantized capillary surface waves, or ripplons, earlier proposed by Atkins [7] in order to explain surface tension data, has been clearly proven in experiments with a two-dimensional plasma resonance in surface electrons [9]. Later, ripplons [10] as well as scattering of surface electrons with Fermi quasi-particles from bulk liquid [11] were detected on liquid 3 He. Soon after that, it was found that the mobility of surface electrons on 3 He deviates drastically from the single-electron-ripplon scattering theory below 70 mK [12].…”

Nonlinear transport of the Wigner solid on normal and superfluid 3He surfaces

“…We had previously found that at sufficiently weak driving, the WS transport on liquid 3 He is Ohmic [3,5]. In the Ohmic regime, the WS mobility m has an interesting temperature dependence, and it is well explained by a linear theory [4].…”

“…We have measured the low-frequency ac resistance R of the SSE by a capacitive coupling method [3,9]: A Corbino disk (30 and 20 mm in outer and inner diameters, respectively, and 0.1 mm gap width) is located 1.0 min beneath the helium surface. The SSE were formed by thermoionic emission of a tungsten filament, and were kept by a static holding electric field E t between the Corbino electrode and a disk electrode which is located 2.5 mm above the liquid surface.…”

“…These nonlinear phenomena are observed both on superfluid 4 He and on normal Fermi liquid 3 He, but only in a magnetic field [6,9]. A key aspect of the theoretical interpretation of the nonlinear WS transport discussed previously [7,8] is high Hall velocity of the electrons.…”

“…On superfluid 4 He, the Ohmic (linear) transport observed under weak drive is explained well in terms of 2D phonon scattering by ripplons. On the 3 He surface, the WS transport is prevailed by bulk quasiparticle reflection from the dimples [2][3][4][5].…”