Zaur Z. Alisultanov | Searcharxiv

arXiv2023

Phase Shift in AC Magnetocaloric Effect Measurements as an Indicator of the Order of Magnetic Phase Transitions

It is shown that the phase shift between an applied weak alternating magnetic field and the magnetocaloric response signal of the magnetic material is drastically sensitive to the order of phase transition. Namely, at the second-order phase transition, the phase shift does not depend on the magnetic field magnitude, while in the first-order phase transition this one depends significantly on the field strength. We have shown that this effect follows from the general critical dynamics theory.

cond-mat.str-el↗

arXiv2021

Towards the theory of types III and IV non-Hermitian Weyl fermions

We develop the non-Hermitian Hamiltonian formalism to describe Weyl fermions of type III and IV. The spectrum of Hamiltonian has an unusual type of anisotropy. Namely, the hermiticity of Hamiltonian strongly depends on the direction in momentum space: for some directions the spectrum is real, in contrast for other directions it becomes complex. This fact leads to non-trivial adiabatic evolution and fractional Chern number. Additionally, we demonstrate that the non-Hermitian Hamiltonian can be regarded as a one-particle problem in context of topological band theory.

cond-mat.str-el↗

arXiv2019

Relativistic Mechanism of Chiral Magnetic Current in Weyl Semimetals with Tilted Dispersion

The chiral magnetic effect is a one of the exotic bulk transport properties of the Weyl semimetals. Because of the Nielsen-Ninomiya "no-go theorem", the total chiral magnetic current is absent in the equilibrium state. One of the mechanisms for generating this current is the chiral anomaly. This phenomenon is the anomalous nonconservation of chiral charge for massless relativistic particles. It can be realized by parallel magnetic and electric fields, and it leads to such new transport phenomenon as the negative longitudinal magnetoresistance. Using a simple theory (we consider both linearized and lattice model), we have shown, that in Weyl metals with tilted dispersion another mechanism of the chiral magnetic current is possible. It is not associated with the chiral anomaly. The new transport mechanism is based on the relativistic effect of electric field on Landau levels. This effect is that an electric field changes the distance between the Landau levels, and also changes the effective velocity along magnetic field. At presence of a tilt in the spectrum, this velocity renormalization is differ for different Weyl points. This leads to a non-zero resulting drift velocity. As a consequence, an electrical current arises along the magnetic field. The induced by this mechanism the electric current is proportional to the pseudoscalar product of the fields and directed along the magnetic field, that differs it from the Hall current. At the same time, the conductivity corresponding to this transport mechanism does not depend on the scattering time like the Hall conductivity. Thus, we have proposed a new anomalous transport mechanism in the Weyl semimetal, which is not associated with the chiral anomaly.

cond-mat.str-el↗