S. V. Syzranov

Effect of radiation on transport in graphene

We study transport properties of graphene-based

Critical transport in weakly disordered semiconductors and semimetals.

p\text{\ensuremath{-}}n

Unconventional localization transition in high dimensions

junctions irradiated by electromagnetic field (EF). The resonant interaction of propagating quasiparticles with an external monochromatic radiation opens dynamical gaps in their spectrum, resulting in a strong modification of current-voltage characteristics of the junctions. The values of the gaps are proportional to the amplitude of EF. We find that the transmission of the quasiparticles in the junctions is determined by the tunneling through the gaps and can be fully suppressed when applying a sufficiently large radiation power. However, EF can not only suppress the current but also generate it. We demonstrate that if the height of the potential barrier exceeds a half of the photon energy, the directed current (photocurrent) flows through the junction without any dc bias voltage applied. Such a photocurrent arises as a result of inelastic quasiparticle tunneling assisted by one- or two-photon absorption. We calculate current-voltage characteristics of diverse graphene-based junctions and estimate their parameters necessary for the experimental observation of the photocurrent and transmission suppression.

Spin–orbital dynamics in a system of polar molecules

Motivated by Weyl semimetals and weakly doped semiconductors, we study transport in a weakly disordered semiconductor with a power-law quasiparticle dispersion ξ_{k}∝k^{α}. We show, that in 2α dimensions short-correlated disorder experiences logarithmic renormalization from all energies in the band. We study the case of a general dimension d using a renormalization group, controlled by an ϵ=2α-d expansion. Above the critical dimensions, conduction exhibits a localization-delocalization phase transition or a sharp crossover (depending on the symmetries of the Hamiltonian) as a function of disorder strength. We utilize this analysis to compute the low-temperature conductivity in Weyl semimetals and weakly doped semiconductors near and below the critical disorder point.

Photocurrent in a visible-light graphene photodiode

We study non-interacting systems with a power-law quasiparticle dispersion

Emergent Weyl excitations in systems of polar particles

\xi_{\bf k}\propto k^\alpha

Conductivity of a Weyl semimetal with donor and acceptor impurities

and a random short-range-correlated potential. We show that, unlike the case of lower dimensions, for

Strongly anisotropic Dirac quasiparticles in irradiated graphene

d>2\alpha

Pair-breaking due to orbital magnetism in iron-based superconductors

there exists a critical disorder strength (set by the band width), at which the system exhibits a disorder-driven quantum phase transition at the bottom of the band, that lies in a universality class distinct from the Anderson transition. In contrast to the conventional wisdom, it manifests itself in, e.g., the disorder-averaged density of states. For systems in symmetry classes that permit localisation, the striking signature of this transition is a non-analytic behaviour of the mobility edge, that is pinned to the bottom of the band for subcritical disorder and grows for disorder exceeding a critical strength. Focussing on the density of states, we calculate the critical behaviour (exponents and scaling functions) at this novel transition, using a renormalisation group, controlled by an

dc conductivity of an array of Josephson junctions in the insulating state.

\varepsilon=2\alpha-d