D. A. Bagrets

Sachdev–Ye–Kitaev model as Liouville quantum mechanics

Abstract We show that the proper inclusion of soft reparameterization modes in the Sachdev–Ye–Kitaev model of N randomly interacting Majorana fermions reduces its long-time behavior to that of Liouville quantum mechanics. As a result, all zero temperature correlation functions decay with the universal exponent ∝ τ − 3 / 2 for times larger than the inverse single particle level spacing τ ≫ N ln ⁡ N . In the particular case of the single particle Green function this behavior is manifestation of the zero-bias anomaly, or scaling in energy as ϵ 1 / 2 . We also present exact diagonalization study supporting our conclusions.

Enhanced Shot Noise in Resonant Tunneling via Interacting Localized States

In a variety of mesoscopic systems shot noise is seen to be suppressed in comparison with its Poisson value. In this work we observe a considerable enhancement of shot noise in the case of resonant tunneling via localized states. We present a model of correlated transport through two localized states which provides both a qualitative and a quantitative description of this effect.

Power-law out of time order correlation functions in the SYK model

We evaluate the finite temperature partition sum and correlation functions of the Sachdev–Ye–Kitaev (SYK) model. Starting from a recently proposed mapping of the SYK model onto Liouville quantum mechanics, we obtain our results by exact integration over conformal Goldstone modes reparameterizing physical time. Perhaps, the least expected result of our analysis is that at time scales proportional to the number of particles the out of time order correlation function crosses over from a regime of exponential decay to a universal t−6 power-law behavior.

Resonant spin-dependent tunneling in spin-valve junctions in the presence of paramagnetic impurities

The tunnel magnetoresistance (TMR) of F/O/F magnetic junctions, (Fs are ferromagnetic layers and O is an oxide spacer) in the presence of magnetic impurities within the barrier, is investigated. We assume that magnetic couplings exist both between the spin of impurity and the bulk magnetization of the neighboring magnetic electrode, and between the spin of impurity and the spin of tunneling electron. Consequently, the resonance levels of the system formed by a tunneling electron and a paramagnetic impurity with spin S=1, are a sextet. As a result the resonant tunneling depends on the direction of the tunneling electron spin. At low temperatures and zero bias voltage the TMR of the considered system may be larger than TMR of the same structure without paramagnetic impurities. It is calculated that an increase in temperature leads to a decrease in the TMR amplitude due to excitation of spin-flip processes resulting in mixing of spin up and down channels. It is also shown that asymmetry in the location of the impurities within the barrier can lead to asymmetry in

Circuit theory for full counting statistics in multiterminal circuits

I(V)

Nonintegrability of two problems in vortex dynamics

characteristics of impurity assisted current and two mechanisms responsible for the origin of this effect are established. The first one is due to the excitation of spin-flip processes at low voltages and the second one arises from the shift of resonant levels inside the insulator layer under high applied voltages.

Full current statistics in the regime of weak coulomb interaction

We propose a theory that treats the current, noise, and, generally, the full current statistics of electron transfer in a mesoscopic system in a unified, simple, and efficient way. The theory appears to be a circuit theory of 2 x 2 matrices associated with Keldysh Green functions. We illustrate the theory by considering the big fluctuations of currents in various three-terminal circuits.

Full counting statistics of interacting electrons

An analysis is presented of two problems in vortex dynamics whose equations can be written in the Hamiltonian form. They are: the interaction of three coaxial vortex rings and the motion of four point vortices on a sphere. The nonintegrability of these problems in the restricted formulation is demonstrated analytically by the method of split separatrices, using a small parameter. (c) 1997 American Institute of Physics.

Full counting statistics in the self-dual interacting resonant level model

We evaluate the full statistics of the current via a Coulomb island that is strongly coupled to the leads. This strong coupling weakens Coulomb interaction. We show that in this case the effects of the interaction can be incorporated into the renormalization of transmission eigenvalues of the scatterers that connect the island and the leads. We evaluate the Coulomb blockade gap in the current-voltage characteristics, the value of the gap being exponentially suppressed as compared to the classical charging energy of the island.

Effective Field Theory of the Disordered Weyl Semimetal.

In order to fully characterize the noise associated with electron transport, with its severe consequences for solid-state quantum information systems, the theory of full counting statistics has been developed. It accounts for correlation effects associated with the statistics and effects of entanglement, but it remains a non-trivial task to account for interaction effects. In this article we present two examples: we describe electron transport through quantum dots with strong charging effects beyond perturbation theory in the tunneling, and we analyze current fluctuations in a diffusive interacting conductor.