Recent Developments in the Field of the Metal-Insulator Transition in Two Dimensions

Abstract

We review the latest developments in the field of the metal-insulator transition in strongly-correlated two-dimensional electron systems. Particular attention is given to recent discoveries of a sliding quantum electron solid and interaction-induced spectrum flattening at the Fermi level in high-quality silicon-based structures.

Fermion Condensation, T-Linear Resistivity, and Planckian Limit

“…The flat bands are formed by interaction (while a geometric frustration can help the process), and have a special T − dependence: At rising temperatures, a nonzero slope appears in the ε(k) dispersion law, while the quasiparticle width γ ∝ T [5,6]. This observation is in accordance with experimental data, see e. g. [7][8][9]. Moreover, the FC theory allows one to describe adequately (both qualitatively and quantitatively) the above NFL behavior of strongly correlated Fermi systems [1,2,6,[10][11][12][13].…”

Competing correlated states around the zero-field Wigner crystallization transition of electrons in two dimensions

“…In spite of decades of research efforts, [8][9][10][11][12] many aspects of the phase diagram of a strongly interacting 2DES in the limit of zero temperature and zero magnetic field remain clouded in the range of 25 < r s < 40, where QMC calculations predict a breakdown of the Fermi liquid (FL) state. One of the main obstacles has been the tradeoff of interaction and disorder strengths in these platforms; namely, the cleanest systems, such as electrondoped GaAs, are also typically the ones that are relatively weakly interacting, while those with stronger interactions tend to be more disordered.…”

“…B c can be interpreted as the critical field required to reach full spin polarization. [8][9][10][11][12] Figure 3b plots the ratio ρ B /ρ B=sat in the (B x ,n)-plane, with orange regions associated with a fully spin polarized 2DES. The data in Fig.…”

Spin effect on the low-temperature resistivity maximum in a strongly interacting 2D electron system

“…The zero-magnetic-field metal-insulator transition has been reported in a number of strongly-correlated twodimensional (2D) electron systems in semiconductors [1][2][3][4][5][6][7][8][9] (for a recent review, see Ref. [10]), in quasi-2D organic charge-transfer salts (Mott organics) [11], as well as in 2D transition metal dichalcogenides [12][13][14]. The hallmark of the low-temperature resistivity ρ on the metallic side near the metal-insulator transition is a nonmonotonic ρ(T ): when the temperature is decreased, the resistivity first increases, reaching a maximum at a temperature T max , and then drops at lower temperatures.…”