Electron-drag effects in coupled electron systems

Abstract

The advancement of fabrication and lithography techniques of semiconductors have made it possible to study bi-layer systems made of two electronic layers separated by distances of several hundred Angstroms. In this situation the electrons in layer 1 are distinguishable from those in layer 2, and can communicate through the direct inter-layer Coulomb interaction. In particular, if a current is applied to one of the layers, the electrons in the second will be dragged giving rise to a transresistance ρ D . In this article we review recent theoretical and experimental developments in the understanding of this effect. At very low temperatures it turns out that phonons dominate the transresistance. The direct Coulomb interaction and plasmon excitations are important at temperatures T > 0.1T F , with T F the Fermi temperature. If a magnetic field is applied the transresistance is increased, in a very interesting interplay between ρ D and Landau quantization. The non-dissipative drag is also reviewed.

Anomalous low-temperature Coulomb drag in graphene-GaAs heterostructures

“…47 to include effects due to the finite width of the GaAs quantum well (see Supplementary Note 4). This shows that the experimental results in this temperature range are consistent with the canonical Fermi-liquid prediction 24,[43][44][45][46][47][48][49][50] , that is, R D pT 2 (see also Fig. 3a), as constrained by the available phase-space of the initial and final states involved in the scattering process.…”

“…We focus on the Coulomb drag transport measurements, which are sensitive to many-body effects. We find that the Coulomb drag resistivity significantly increases for temperatures To5-10 K, with a notable departure from the T 2 temperature dependence expected in a weakly correlated Fermi-liquid scenario 24 . The low-temperature data follow a logarithmic law, without the onset of saturation in the case of bilayer graphene/GaAs samples.…”

“…Experimentally, the Coulomb drag is routinely used as a sensitive probe of strong correlations including transitions to the superconducting state 40 , metal-insulator transitions 41 and Luttinger liquid correlations 42 in quantum wires, and exciton condensation in quantum Hall bilayers 9 . In a Coulomb drag experiment 24,43,44 , a current source is connected to one of the two layers (the active or drive layer). The other layer (the passive layer) is connected to an external voltmeter so that the layer can be assumed to be an open circuit (no current can flow in it).…”

“…The voltage drop V drag related to this field is then measured. The quantity R D is defined as the ratio V drag /I drive and is determined by the rate at which momentum is transferred between quasiparticles in the two layers 24 . Before the Coulomb drag experiments, we performed magnetotransport measurements at 4 K, as for Fig.…”

Exchange and correlation effects on plasmon dispersions and Coulomb drag in low-density electron bilayers

“…The drag effect complements and enriches the traditional experimental methods and in the last decade has proved to be a powerful tool to probe interlayer electron-electron ͑e-e͒ interaction. 5 Recently the drag measurements have been extended to the limit of very low carrier concentrations. The dimensionless parameter r s = ͱ 2/͑k F a B * ͒, which describes the carrier density n and measures the strength of the electron-electron interaction, 6 varies approximately from 10 to 20 in the experiment on hole samples by Pillarisetty et al 7,8 Here k F = ͱ 2 n is the Fermi wave vector, and a B * = ប 2 0 / m * e 2 is the effective Bohr radius, with 0 the static dielectric constant and m * the effective mass of the carriers; a B * = 9.79 and 3.45 nm, respectively, in the conduction ͑m e * = 0.067m 0 ͒ and valence ͑m h * = 0.19m 0 ͒ bands of GaAs.…”