Colloquium: Transport in strongly correlated two dimensional electron fluids

Abstract

We present an overview of the measured transport properties of the two dimensional electron fluids in high mobility semiconductor devices with low electron densities, and of some of the theories that have been proposed to account for them. Many features of the observations are not easily reconciled with a description based on the well understood physics of weakly interacting quasiparticles in a disordered medium. Rather, they reflect new physics associated with strong correlation effects, which warrant further study.

Coulomb drag

“…Early work on frictional drag was reviewed by . Various experimental aspects were discussed in reviews on exciton condensates (Eisenstein, 2014;Snoke, 2002), electron-hole bilayers (Das Gupta et al, 2011), strongly-correlated 2D electron fluids (Spivak et al, 2010), and 1D ballistic electron systems (Debray et al, 2002). A discussion of drag in strong magnetic fields was included in a review of magnetotransport in 2D electron systems (Dmitriev et al, 2008).…”

“…The theory of Coulomb drag between two 2DEGs was extended to dilute 2D hole systems (Hwang et al, 2003) and to the cases where one allows for certain tunneling processes between the layers (Oreg and Halperin, 1999;Oreg and Kamenev, 1998), interlayer disorder correlations (Gornyi et al, 1999;Hu, 2000a), in-plane potential modulation (Alkauskas et al, 2002), and disorder inhomogeneities (Apalkov and Raikh, 2005;Spivak and Kivelson, 2005;Zou et al, 2009Zou et al, , 2010. Theory of Coulomb drag between composite fermions was generalized to include phonon-mediated coupling (Bønsager et al, 2000;Khveshchenko, 2000).…”

Exchange energy enhancedg-factors obtained from Landau fan diagrams at low magnetic fields

“…In lower magnetic field and in lower electron density, the ratios of the electron-electron and electron-hole energies to the cyclotron energy increase, and phenomena due to the electron-electron and electron-hole interactions are expected to be more prominent. In fact, it has been found in GaAs/AlGaAs heterostructures and in Si inversion layers that the electron effective mass (m * e ) and spin susceptibility of electrons χ = m * e g * increase with a decrease in electron density, [5][6][7][8] where g * is the electron effective g factor.…”

Overlapping-Gate Architecture for Silicon Hall Bar MOSFET Devices in the Low Electron Density and High Magnetic Field Regime

“…In that case a voltage bias applied across the source and drain contact of a Hall bar MOSFET will mostly fall across the contacts (and not across the channel) and therefore magneto-transport measurements become challenging. However, from a physical point of view, the study of MOSFET nanostructures in the low electron density regime is very interesting (impurity limited mobility [1], carrier interactions [2,3] and spin-dependent transport [4]) and it is therefore important to come up with solutions [5,6] that work around the problem of a high contact resistance in such devices (c.f. Fig.…”