Strain-Induced Quasi-1D Channels in Twisted Moiré Lattices.

We study the effects of strain in moiré systems composed of honeycomb lattices. We elucidate the formation of almost perfect one-dimensional moiré patterns in twisted bilayer systems. The formation of such patterns is a consequence of an interplay between twist and strain which gives rise to a collapse of the reciprocal space unit cell.

Quantum Diffusion in the Lowest Landau Level of Disordered Graphene.

Electronic transport in the lowest Landau level of disordered graphene sheets placed in a homogeneous perpendicular magnetic field is a long-standing and cumbersome problem which defies a conclusive solution for several years. Because the modeled system lacks an intrinsic small parameter, the theoretical picture is infested with singularities and anomalies. We propose an analytical approach to the conductivity based on the analysis of the diffusive processes, and we calculate the density of states, the diffusion coefficient and the static conductivity.

Anomalous Josephson Effect of s-Wave Pairing States in Chiral Double Layers.

We consider s-wave pairing in a double layer of two chiral metals due to interlayer Coulomb interaction and study the Josephson effect near a domain wall, where the sign of the order parameter jumps. The domain wall creates two evanescent modes at the exceptional zero-energy point, whose superposition is associated with currents flowing in different directions in the two layers. Assuming a toroidal geometry, the effective Josephson current winds around the domain walls, whose direction is determined by the phase difference of the complex coefficients of the superimposed zero-energy modes.

Finite-size scaling in a 2D disordered electron gas with spectral nodes.

We study the DC conductivity of a weakly disordered 2D electron gas with two bands and spectral nodes, employing the field theoretical version of the Kubo-Greenwood conductivity formula. Disorder scattering is treated within the standard perturbation theory by summing up ladder and maximally crossed diagrams. The emergent gapless (diffusion) modes determine the behavior of the conductivity on large scales.

Spectral function and quasiparticle damping of interacting Bosons in two dimensions.

We employ the functional renormalization group to study dynamical properties of the two-dimensional Bose gas. Our approach is free of infrared divergences, which plague the usual diagrammatic approaches, and is consistent with the exact Nepomnyashchy identity, which states that the anomalous self-energy vanishes at zero frequency and momentum. We recover the correct infrared behavior of the propagators and present explicit results for the spectral line shape, from which we extract the quasiparticle dispersion and damping.

Two-parameter scaling of correlation functions near continuous phase transitions.

We discuss the order parameter correlation function in the vicinity of continuous phase transitions using a two-parameter scaling form G(k)=kc(-2)g(kxi,k/kc), where k is the wave vector and xi is the correlation length, and the interaction-dependent nonuniversal momentum scale kc remains finite at the critical fixed point. The correlation function describes the entire critical regime and captures the classical to critical crossover. One-parameter scaling is recovered only in the limit k/kc-->0.