Electron localization properties in graphene

We study localization properties of the Dirac-like electronic states in monolayers of graphite. In the framework of a general disorder model, we discuss the conditions under which such standard localization effects as the logarithmic temperature-dependent conductivity correction appear to be strongly suppressed, as compared to the case of a two-dimensional electron gas with parabolic dispersion, in agreement with recent experimental observations

Quantum impurity models of noisy qubits

We demonstrate that the problem of coupled two-level systems ("qubits") which are also subject to a generic (sub-)Ohmic dissipative environment belongs to the same class of models as those describing (non)magnetic impurities embedded in strongly correlated systems. A further insight into the generalized single- and two-impurity Bose/Fermi Kondo models enables one to make specific recommendations towards a systematic engineering of highly coherent multiqubit assemblies for potential applications in quantum information processing

One syk single electron transistor

We study the behaviour of a single electron transistor (SET) represented by a dissipative tunnel junction between a pair of quantum dots described by two (possibly, different) Sachdev–Ye–Kitaev (SYK) models. A combined influence of the soft collective charge and energy modes on charge transport is discussed, alongside the competing effects of the Coulomb blockade and emergent Kondo resonances which might all conspire to result in a non-monotonic behaviour of the system’s conductance

Phonon-mediated transresistivity in a double-layer composite Fermion system

We consider the frictional drag in a double-layer system of two-dimensional electrons in the half-filled lowest Landau level. At sufficiently large interlayer separations the drag is dominated by the exchange of acoustic phonons and exhibits a variety of dependencies on temperature and distance between the layers. In all of the regimes, the phonon-mediated drag is found to be strongly enhanced compared to that in zero magnetic field

On a (Pseudo)holographic nature of the syk-like models

Some generalizations of the Sachdev–Ye–Kitaev (SYK) model and different patterns of their reparametrization symmetry breaking are discussed. The analysis of such (pseudo)holographic systems relates their generalized onedimensional Schwarzian dynamics to (quasi) two-dimensional Liouvillian quantum mechanics. As compared to the original SYK case, the latter might be dissipative or have discrete states in its spectrum, either of which properties alters thermodynamics and correlations while preserving the underlying SL(2, R) symmetry

Article seeking to develop global syk-ness

Inspired by the recent interest in the Sachdev–Ye–Kitaev (SYK) model, we study a class of multi-flavored one-and two-band fermion systems with no bare dispersion. In contrast to the previous work on the SYK model that would routinely assume spatial locality, thus unequivocally arriving at the so-called ‘locally-critical’ scenario, we seek to attain a spatially-dispersing ‘globally-SYK’ behavior. To that end, a variety of the Lorentz-(non)invariant space-and/or-time dependent algebraically decaying interaction functions is considered and some of the thermodynamic and transport properties of such systems are discussed

Elusive physical electron propagator in QED-like effective theories

We study the previously conjectured form of the physical electron propagator and its allegedly Luttinger type of behavior in the theory of the pseudogap phase of high-temperature copper-oxide superconductors and other effective QED-like models. We demonstrate that, among a whole family of seemingly gauge-invariant functions, the conjectured "stringy ansatz" for the electron propagator is the only one that is truly invariant. However, contrary to the results of the earlier works, it appears to have a negative anomalous dimension, which makes it a rather poor candidate to the role of the physical electron propagator. Instead, we argue that the latter may, in fact, feature a "super-Luttinger" behavior characterized by a faster than any power-law decay: G(x) ~ exp(-const ln^2|x|).Comment: Latex, 10 pages, no figure

Effect of fermi surface curvature on low-energy properties of fermions with singular interactions

We discuss the effect of Fermi surface curvature on long-distance or time asymptotic behaviors of two-dimensional fermions interacting via a gapless mode described by an effective gauge-field-like propagator. By comparing the predictions based on the idea of multidimensional bosonization with those of the strong-coupling Eliashberg approach, we demonstrate that an agreement between the two requires a further extension of the former technique

Excitonic instability in layered degenerate semimetals

We study excitonic pairing in quasi-two-dimensional degenerate semimetals such as graphite, where the electron density of states nearly vanishes at the Fermi level and, therefore, the Coulomb interactions remain unscreened. By focusing on the Dirac-like low-energy electronic excitations and numerically solving a non-linear gap equation for the excitonic order parameter, we obtain a critical value of the Coulomb coupling and establish the Kosterlitz-Thouless-like nature of the putative semimetal-to-excitonic insulator transition which can also be identified as a formal analog of chiral symmetry breaking in relativistic fermion theories

Piezoelectric electron-phonon interaction in impure semiconductors: Two-dimensional electrons versus composite fermions

We study the effects of piezoelectric coupling between two-dimensional electrons and bulk phonons in cases of both zero and strong perpendicular magnetic fields, the latter corresponding to even-denominator filling fractions. In contrast to the case of coupling via the deformation potential, the leading contributions due to impurity-renormalized electron-phonon vertices are not exactly canceled by processes of inelastic electronimpurity scattering. Electron energy relaxation time, diffusion correction to the conductivity, and the phononemission rate by hot electrons are computed for realistic GaAs/AlxGa12xAs heterostructures