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M. A. Zubkov

Publications and source records attributed to M. A. Zubkov.

At least 37 records · Page 2Linked to original sources
arXiv2023

Precise Wigner-Weyl calculus for the honeycomb lattice

In this paper we propose the precise Wigner-Weyl calculus for the lattice models defined on the honeycomb lattice. We construct two symbols of operators: the $\mathscr{B}$-symbol, which is similar to the symbol introduced by F. Buot, and the $W$ (or, Weyl) symbol. The latter possesses the set of useful properties. These identities allow us to use it in physical applications. In particular, we derive topological expression for the Hall conductivity through the Wigner transformed Green function. This expression may be used for the description of quantum Hall effect in the systems with artificial honeycomb lattice, when magnetic flux through the lattice cell is of the order of elementary quantum of magnetic flux.

cond-mat.mes-hall↗
arXiv2022

Quark mass generation due to scalar fields with zero dimension

We propose a model of dynamical symmetry breaking, in which a new type of fundamental scalar fields of zero mass-dimension mediate the couplings of fermions to the gravitational field, represented here as a tetrad field in the same manner as Riemann-Cartan gravity. In our model, the tetrad couples to the standard model fermions non-minimally, and the very coupling coefficients are the fundamental scalar fields. There are exactly 36 scalar fields in the model, which are distinguishable by flavor indices on the fields. This is the precise number of zero dimension scalar fields that leads to a vanishing Weyl anomaly and a vanishing vacuum energy. Precisely the same number of these very same scalar fields is required for the coupling of all of the different standard model fermions to the vielbein field. At the same time their interaction with fermions gives rise to fermion mass terms, without the need to introduce a fundamental Higgs field. Within the proposed theory we construct a toy model that deals solely with the top and bottom quarks, and we demonstrate that their observable masses can appear in the action dynamically. Moreover, this mechanism allows for the top and bottom quarks to acquire distinctly different masses, as opposed to our previous, even simpler toy model that contained only the top quark.

hep-th↗
arXiv2022

Chiral Magnetic Effect out of equilibrium

We consider relativistic fermionic systems in lattice regularization out of equilibrium. The chiral magnetic conductivity $σ_{CME}$ is calculated in spatially infinite system for the case when the chiral chemical potential depends on time while the system initially was in thermal equilibrium at small but nonzero temperature. We find that the frequency dependent $σ_{CME}(ω)$ for any nonzero $ω$ both in the limits $ω\ll T$ and $ω\gg T$ is equal to its conventional value $1$ when the lattice model approaches continuum limit. Notice that $σ_{CME} = 0$ for the case when the chiral chemical potential does not depend on time at all. We therefore confirm that the limit of vanishing $ω$ is not regular for the spatially infinite systems of massless fermions.

hep-ph↗
arXiv2022

Topological quantization of Fractional Quantum Hall conductivity

We consider the quantum Hall effect (QHE) in a system of interacting electrons. Our formalism is valid for systems in the presence of an external magnetic field, as well as for systems with a nontrivial band topology. That is, the expressions for the conductivity derived are valid for both the ordinary QHE and for the intrinsic anomalous QHE. The expression for the conductivity applies to external fields that may vary in an arbitrary way, and takes into account disorder. It is assumed that the ground state of the system is degenerate. We represent the QHE conductivity as $\frac{e^2}{h} \times \frac{\cal N}{K}$, where $K$ is the degeneracy of the ground state, while $\cal N$ is the topological invariant composed of the Wigner - transformed multi - leg Green functions. $\cal N$ takes discrete values, which gives rise to quantization of the fractional QHE conductivity.

cond-mat.mes-hall↗
arXiv2022

Influence of interactions on Integer Quantum Hall Effect

Conductivity of Integer Quantum Hall Effect (IQHE) may be expressed as the topological invariant composed of the two - point Green function. Such a topological invariant is known both for the case of homogeneous systems with intrinsic Anomalous Quantum Hall Effect (AQHE) and for the case of IQHE in the inhomogeneous systems. In the latter case we may speak, for example, of the AQHE in the presence of elastic deformations and of the IQHE in presence of magnetic field. The topological invariant for the general case of inhomogeneous systems is expressed through the Wigner transformed Green functions and contains Moyal product. When it is reduced to the expression for the IQHE in the homogeneous systems the Moyal product is reduced to the ordinary one while the Wigner transformed Green function (defined in phase space) is reduced to the Green function in momentum space. Originally the mentioned above topological representation has been derived for the non - interacting systems. We demonstrate that in a wide range of different cases in the presence of interactions the Hall conductivity is given by the same expression, in which the noninteracting two - point Green function is substituted by the complete two - point Green function with the interactions taken into account. Several types of interactions are considered including the contact four - fermion interactions, Yukawa and Coulomb interactions. We present the complete proof of this statement up to the two loops, and argue that the similar result remains to all orders of perturbation theory. It is based on the incorporation of Wigner - Weyl calculus to the perturbation theory. We, therefore, formulate Feynmann rules of diagram technique in terms of the Wigner transformed propagators.

cond-mat.mes-hall↗
arXiv2022

Fundamental scalar field with zero dimension from anomaly cancelations

In this article a novel mechanism for dynamical electroweak symmetry breaking and the ensuing appearance of fermion mass terms in the action is proposed. The action contains massless fermions of the SM coupled to gravity through a new type of non-minimal coupling to the vielbein field. The corresponding coupling constants in our approach become zero-dimension scalar fields. Such scalar fields provide the cancellation of the Weyl anomaly \cite{Boyle:2021jaz}.

hep-th↗
arXiv2022

Riemann-Cartan gravity with dynamical signature

Model of Riemann-Cartan gravity with varying signature of metric is considered. The basic dynamical variables of the formalism are vierbein, spin connection, and an internal metric in the tangent space. The corresponding action contains new terms, which depend on these fields. In general case the signature of the metric is determined dynamically. The Minkowski signature is preferred dynamically because the configurations with the other signatures are dynamically suppressed. We also discuss briefly the motion of particles in the background of the modified black hole configuration, in which inside the horizon the signature is that of Euclidean space - time.

gr-qc↗
arXiv2022

Multilayer Haldane model

We propose the model of layered materials, in which each layer is described by the conventional Haldane model, while the inter - layer hopping parameter corresponds to the ABC stacking. We calculate the topological invariant $N_3$ for the resulting model, which is responsible for the conductivity of intrinsic quantum Hall effect. It has been shown that in a certain range of the values of interlayer hopping parameter, the value of $N_3$ is equal to the number of layers multiplied by the topological invariant of each layer. At the same time this value may be calculated using the low energy effective theory.

cond-mat.mes-hall↗
arXiv2022

Wigner-Weyl calculus in description of non-dissipative transport phenomena

Application of Wigner-Weyl calculus to the investigation of non-dissipative transport phenomena is reviewed. We focus on the quantum Hall effect, Chiral Magnetic effect, and Chiral separation effect, and discuss the role of interactions, inhomogeneity, and deviations from equilibrium.

cond-mat.mes-hall↗
arXiv2021

Hall conductivity as the topological invariant in magnetic Brillouin zone

Hall conductivity for the intrinsic quantum Hall effect in homogeneous systems is given by the topological invariant composed of the Green function depending on momentum of quasiparticle. This expression reveals correspondence with the mathematical notion of the degree of mapping. A more involved situation takes place for the Hall effect in the presence of external magnetic field. In this case the mentioned expression remains valid if the Green function is replaced by its Wigner transformation while ordinary products are replaced by the Moyal products. Such an expression, unfortunately, is much more complicated and might be useless for the practical calculations. Here we represent the alternative representation for the Hall conductivity of a uniform system in the presence of constant magnetic field. The Hall conductivity is expressed through the Green function taken in Harper representation, when its nonhomogeneity is attributed to the matrix structure while functional dependence is on one momentum that belongs to magnetic Brillouin zone. Our results were obtained for the non - interacting systems. But we expect that they remain valid for the interacting systems as well. We, therefore, propose the hypothesis that the obtained expression may be used for the topological description of fractional quantum Hall effect.

cond-mat.mes-hall↗
arXiv2021

Anomalous fractional quantum Hall effect and multi-valued Hamiltonians

We discuss anomalous fractional quantum Hall effect that exists without external magnetic field. We propose that excitations in such systems may be described effectively by non-interacting particles with the Hamiltonians defined on the Brillouin zone with a branch cut. Hall conductivity of such a system is expressed through the one-particle Green function. We demonstrate that for the Hamiltonians of the proposed type this expression takes fractional values times Klitzing constant. Possible relation of the proposed construction with degeneracy of ground state is discussed as well.

cond-mat.mes-hall↗
arXiv2021

Chiral Separation Effect in lattice regularization

We consider Chiral Separation Effect (CSE) in the lattice regularized quantum field theory. We discuss two types of regularization - with and without exact chiral symmetry. In the latter case this effect is described by its conventional expression for the massless fermions. This is illustrated by the two particular cases - of Wilson fermions and of the conventional overlap fermions. At the same time in the presence of the exact chiral symmetry the CSE disappears. This is illustrated by the naive lattice fermions, when the contributions of the fermion doublers cancel each other. Another example is the modified version of the overlap regularization proposed recently, where there is the exact chiral symmetry, but as a price for this the fermion doublers become zeros of the Green function. In this case the contribution to the CSE of zeros and poles of the Green function cancel each other.

hep-lat↗
arXiv2021

Classification of emergent Weyl spinors in multi-fermion systems

In the fermionic systems with topologically stable Fermi points the emergent two - component Weyl fermions appear. We propose the topological classification of these fermions based on the two invariants composed of the two - component Green function. We define these invariants using Wigner - Weyl formalism also in case of essentially non - homogeneous systems. In the case when values of these invariants are minimal ($\pm 1$) we deal with emergent relativistic symmetry. The emergent gravity appears, and our classification of Weyl fermions gives rise to the classification of vierbein. Transformations between emergent relativistic Weyl fermions of different types correspond to parity conjugation, time reversal, and charge conjugation.

cond-mat.mes-hall↗
arXiv2021

Anomalous transport phenomena and momentum space topology

Using the derivative expansion applied to the Wigner transform of the two - point Green function this is possible to derive the response of various nondissipative currents to the external gauge fields. The corresponding currents are proportional to the momentum space topological invariants. This allows to analyse systematically various anomalous transport phenomena including the anomalous quantum Hall effect and the chiral separation effect. We discuss the application of this methodology both to the solid state physics and to the high energy physics.

hep-ph↗
arXiv2021

Momentum Space Topology and Non-Dissipative Currents

Relativistic heavy ion collisions represent an arena for the probe of various anomalous transport effects. Those effects, in turn, reveal the correspondence between the solid state physics and the high energy physics, which share the common formalism of quantum field theory. It may be shown that for the wide range of {field-theoretic} models, the response of various nondissipative currents to the external gauge fields is determined by the momentum space topological invariants. Thus, the anomalous transport appears to be related to the investigation of momentum space topology -- the approach developed earlier mainly in the condensed matter theory. Within this methodology we analyse systematically the anomalous transport phenomena, which include, in particular, the anomalous quantum Hall effect, the chiral separation effect, the chiral magnetic effect, the chiral vortical effect and the rotational Hall effect.

hep-ph↗
arXiv2021

Hall conductivity as topological invariant in phase space

It is well known that the quantum Hall conductivity in the presence of constant magnetic field is expressed through the topological TKNN invariant. The same invariant is responsible for the intrinsic anomalous quantum Hall effect (AQHE), which, in addition, may be represented as one in momentum space composed of the two point Green's functions. We propose the generalization of this expression to the QHE in the presence of non-uniform magnetic field. The proposed expression is the topological invariant in phase space composed of the Weyl symbols of the two-point Green's function. It is applicable to a wide range of non-uniform tight-binding models, including the interacting ones.

cond-mat.mes-hall↗
arXiv2021

Absence of equilibrium chiral magnetic effect

We analyse the $3+1$ D equilibrium chiral magnetic effect (CME). We apply derivative expansion to the Wigner transform of the two - point Green function. This technique allows us to express the response of electric current to external electromagnetic field strength through the momentum space topological invariant. We consider the wide class of the lattice regularizations of quantum field theory (that includes, in particular, the regularization with Wilson fermions) and also certain lattice models of solid state physics (including those of Dirac semimetals). It appears, that in these models the mentioned topological invariant vanishes identically at nonzero chiral chemical potential. That means, that the bulk equilibrium CME is absent in those systems.

hep-ph↗