# Pavlo O. SukhachovNorwegian University of Science and Technology | NTNU · Department of Physics

Pavlo O. Sukhachov

Ph. D.

## About

85

Publications

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Introduction

The main scientific interests of Pavlo Sukhachov include the study of various properties of novel topological materials. In particular, he has been investigating a wide range of electronic properties in Weyl and Dirac semimetals such as transport phenomena, electron hydrodynamics, disorder effects, collective excitations, quantum oscillations, interaction effects, topologically protected surface states, i.e., the Fermi arcs, the strain-induced pseudoelectromagnetic fields, etc.

Additional affiliations

August 2023 - February 2024

September 2020 - August 2023

April 2019 - June 2020

Education

December 2014 - February 2016

September 2008 - June 2014

## Publications

Publications (85)

We propose altermagnet-superconductor junctions as a way to achieve a thermoelectric response in metals free of external or stray magnetic fields. We combine qualitative analysis in a simplified model with a more rigorous approach based on the inverse proximity effect in the functional-integral formulation. We show that coupling an altermagnet to a...

Altermagnets are a class of antiferromagnetic materials which have electron bands with lifted spin degeneracy in momentum space but vanishing net magnetization and no stray magnetic fields. Because of these properties, altermagnets have attracted much attention for potential use in spintronics. We here show that despite the absence of bulk magnetiz...

We investigate the Friedel oscillations of the local density of states (LDOS) induced by a single impurity with both a spin-independent potential and an exchange coupling to the electrons in altermagnets and unconventional $p$-wave magnets. We identify features that make the Friedel oscillations and magnetization distinct from other materials with...

We study viscoelastic response in Weyl semimetals with broken time-reversal symmetry. The principal finding is that topology and anisotropy of the Fermi surface are manifested in the viscoelasticity tensor of the electron fluid. In the dynamic (interband) part of this tensor, the anisotropy leads to a qualitatively different, compared with isotropi...

Altermagnets is a class of antiferromagnetic materials which has electron bands with lifted spin degeneracy in momentum space but vanishing net magnetization and no stray magnetic fields. Because of these properties, altermagnets have attracted much attention for potential use in spintronics. We here show that despite the absence of bulk magnetizat...

New unconventional compensated magnets have been discovered in the wake of altermagnets. We introduce a minimal tight-binding model with a spin-split $p$-wave band structure, clarifying the relation between unconventional $p$-wave magnets and helimagnets. Motivated by the tight-binding model, we construct an effective model suitable for analytical...

We propose altermagnet-superconductor junctions as a way to achieve a thermoelectric response in metals free of external or stray magnetic fields. We combine qualitative analysis in a simplified model with a more rigorous approach based on the inverse proximity effect in the functional-integral formulation. We show that coupling an altermagnet to a...

We introduce and classify nonequivalent commensurate stackings for bilayer dice or T3 lattices. For each of the four stackings with vertical alignment of sites in two layers, a tight-binding model and an effective model describing the properties in the vicinity of the threefold band-crossing points are derived. Focusing on these band-crossing point...

We calculate optical conductivity for bilayer dice lattices in commensurate vertically aligned stackings. The interband optical conductivity reveals a rich activation behavior unique for each of the four stackings. We found that the intermediate energy band, which corresponds to the flat band of a single-layer dice lattice, plays a different role f...

We investigate the role of the Bloch functions and superconducting gap symmetries on the formation and properties of impurity-induced resonances in a two-dimensional superconductor, and elucidate their manifestation in scanning tunneling spectra. We use and extend a recently developed scattering approach, conveniently formulating the results in ter...

We evaluate the differential conductance measured in an STM setting at arbitrary electron transmission between STM tip and a 2D superconductor with arbitrary gap structure. Our analytical scattering theory accounts for Andreev reflections, which become prominent at larger transmissions. We show that this provides complementary information about the...

We investigate the role of the Bloch functions and superconducting gap symmetries on the formation and properties of impurity-induced resonances in a 2D superconductor, and elucidate their manifestation in scanning tunneling spectra. We use and extend a recently developed scattering approach, conveniently formulating the results in terms of the pha...

We calculate optical conductivity for bilayer dice lattices whose commensurate stackings and effective models in the vicinity of band-crossing points were considered in our previous work (arXiv:2303.01452). The inter-band optical conductivity reveals a rich activation behavior unique for each of the four stackings. We found that the intermediate en...

We introduce and classify nonequivalent commensurate stackings for bilayer dice or $\mathcal{T}_3$ lattice. For each of the four possible stackings, an effective low-energy model is derived. Although the energy spectrum remains always gapless with three bands interesting at the same point, depending on the stacking, different types of quasiparticle...

We evaluate the differential conductance measured in a scanning tunneling microscopy (STM) setting at arbitrary electron transmission between STM tip and a two-dimensional superconductor with arbitrary gap structure. Our analytical scattering theory accounts for Andreev reflections, which become prominent at larger transmissions. We show that this...

The electric and chiral current response to the time- and coordinate-dependent pseudoelectric field E5 in Weyl semimetals is studied. It is found that E5 leads to an electric current in the direction perpendicular to the field and the wave vector of the field-inducing perturbation. We dubbed this phenomenon the anomalous pseudo-Hall effect. The res...

The electric and chiral current response to the time and coordinate dependent pseudoelectric field $\mathbf{E}_5$ in Weyl semimetals is studied. It is found that $\mathbf{E}_5$ leads to an electric current in the direction perpendicular to the field and the wave vector of the perturbation. We dubbed this effect the anomalous pseudo-Hall effect. The...

The current response to an electromagnetic field in a Weyl or Dirac semimetal becomes nonlocal due to the chiral anomaly activated by an applied static magnetic field. The nonlocality develops under the conditions of the normal skin effect and is related to the valley charge imbalance generated by the joint effect of the electric field of the impin...

We investigate the role of the chiral anomaly in hydrodynamic and crossover regimes of transport in a Weyl or Dirac semimetal film. We show that the magnetic-field-dependent part of the electric conductivity in the direction of the magnetic field develops an unusual nonmonotonic dependence on temperature dubbed the anomalous Gurzhi effect. This eff...

Superfluidity and superconductivity are macroscopic manifestations of quantum mechanics, which have fascinated scientists since their discoveries roughly a century ago. Ever since the initial theories of such quantum fluids were formulated, there has been speculation as to the possibility of multi-component quantum order. A particularly simple mult...

We investigate the role of the chiral anomaly in hydrodynamic and crossover regimes of transport in a Weyl or Dirac semimetal film. We show that the magnetic-field-dependent part of the electric conductivity in the direction of the magnetic field develops an unusual nonmonotonic dependence on temperature dubbed anomalous Gurzhi effect. This effect...

A hydrodynamic flow of electrons driven by an oscillating electric field in Dirac and Weyl semimetals is investigated. It is found that a double-peak profile of the electric current appears and is manifested in a stray magnetic field with peaks in one of the field components. The nontrivial current profile originates from the interplay of viscous a...

Hydrodynamic instabilities driven by a direct current are analyzed in 2D and 3D relativisticlike systems with the Dyakonov-Shur boundary conditions supplemented by a boundary condition for temperature. Besides the conventional Dyakonov-Shur instability for plasmons, we find an entropy wave instability in both 2D and 3D systems. The entropy wave ins...

The current response to an electromagnetic field in a Weyl or Dirac semimetal becomes nonlocal due to the chiral anomaly activated by an applied static magnetic field. The nonlocality develops under the conditions of the normal skin effect and is related to the valley charge imbalance generated by the joint effect of the electric field of the impin...

It is shown that the convective instability in electron fluids in three- and two-dimensional (3D and 2D) Dirac and Weyl semimetals is strongly inhibited. The major obstacles for electron convection are the effects of the Coulomb forces and the momentum relaxation related to the interaction with impurities and phonons. The effect of the Coulomb forc...

A hydrodynamic flow of electrons driven by an oscillating electric field is investigated. It is found that a double-peak profile of the electric current can appear. Such a profile originates from the interplay of viscous and inertial properties of the electron fluid as well as the boundary conditions. The nontrivial profile of the current results i...

We evaluate the sound attenuation in a Weyl semimetal subject to a magnetic field or a pseudomagnetic field associated with a strain. Due to the interplay of intra- and internode scattering processes as well as screening, the fields generically reduce the sound absorption. A nontrivial dependence on the relative direction of the magnetic field and...

Hydrodynamic instabilities driven by a direct current are analyzed in 2D and 3D relativisticlike systems with the Dyakonov-Shur boundary conditions supplemented by a boundary condition for the temperature. Besides the conventional Dyakonov-Shur instability for plasmons, we find an entropy wave instability in both 2D and 3D systems. The entropy wave...

We propose a mechanism to generate a static magnetization via the “axial magnetoelectric effect” (AMEE). Magnetization M∼E5(ω)×E5*(ω) appears as a result of the transfer of the angular momentum of the axial electric field E5(t) into the magnetic moment in Dirac and Weyl semimetals. We point out similarities and differences between the proposed AMEE...

It is shown that the convective instability in electron fluids in three- and two-dimensional (3D and 2D) Dirac and Weyl semimetals is strongly inhibited. The major obstacles for electron convection are the effects of the Coulomb forces and the momentum relaxation related to the interaction with impurities and phonons. The effect of the Coulomb forc...

We evaluate the sound attenuation in a Weyl semimetal subject to a magnetic field or a pseudomagnetic field associated with a strain. Due to the interplay of intra- and inter-node scattering processes as well as screening, the fields generically reduce the sound absorption. A nontrivial dependence on the relative direction of the magnetic field and...

We explore the formation and collective modes of Bose-Einstein condensate of Dirac magnons (Dirac BEC). While we focus on two-dimensional Dirac magnons, an employed approach is general and could be used to describe Bose-Einstein condensates with linear quasiparticle spectrum in various systems. By using a phenomenological multicomponent model of pu...

We propose a mechanism to generate a static magnetization via the axial electromagnetic fields in Dirac and Weyl semimetals via $axial$ $magnetoelectric$ $effect$ (AME). Magnetization ${\bf M} \sim {\bf E}_5(\omega) \times {\bf E}_5^{*}(\omega)$ appears as a result of transfer of the angular momentum of the axial electric field ${\bf E}_5(t)$ into...

The monograph reviews various aspects of electronic properties of Dirac and Weyl semimetals. After a brief discussion of 2D Dirac semimetals, a comprehensive review of 3D materials is given. The description starts from an overview of the topological properties and symmetries of Dirac and Weyl semimetals. In addition, several low-energy models of Di...

Surface plasmon polaritons in a strained slab of a Weyl semimetal with broken time-reversal symmetry are investigated. It is found that the strain-induced axial gauge field reduces frequencies of these collective modes for intermediate values of the wave vector. Depending on the relative orientation of the separation of Weyl nodes in momentum space...

We explore the formation and collective modes of Bose-Einstein condensate of Dirac magnons (Dirac BEC). While we focus on two-dimensional Dirac magnons, an employed approach is general and could be used to describe Bose-Einstein condensates with linear quasiparticle spectrum in various systems. By using a phenomenological multicomponent model of pu...

The superconducting s-wave state in Weyl semimetals in a strong strain-induced pseudomagnetic field is investigated in a model with local four-fermion interaction. It is found that only the internode pairing is possible in the lowest pseudo-Landau level approximation. Unlike the case of the lowest Landau level in a conventional magnetic field, the...

Surface plasmon-polaritons in a strained slab of a Weyl semimetal with broken time-reversal symmetry are investigated. It is found that the strain-induced axial gauge field reduces frequencies of these collective modes for intermediate values of the wave vector. Depending on the relative orientation of the separation of Weyl nodes in momentum space...

The superconducting s-wave state in Weyl semimetals in a strong strain-induced pseudomagnetic field is investigated in a model with local four-fermion interaction. It is found that only the inter-node pairing is possible in the lowest pseudo-Landau level approximation. The analysis of the corresponding gap equation shows that it has only trivial so...

The acoustogalvanic effect is proposed as a nonlinear mechanism to generate a direct electric current by passing acoustic waves in Dirac and Weyl semimetals. Unlike the standard acoustoelectric effect, which relies on the sound-induced deformation potential and the corresponding electric field, the acoustogalvanic one originates from the pseudoelec...

Quasiparticle states in Dirac systems with complex impurity potentials are investigated. It is shown that an impurity site with loss leads to a nontrivial distribution of the local density of states (LDOS). While the real part of defect potential induces a well-pronounced peak in the density of states (DOS), the DOS is either weakly enhanced at sma...

The transport properties and electron states in cylinder nanowires of Dirac and Weyl semimetals are studied paying special attention to the structure and properties of the surface Fermi arcs. The latter make the electric charge and current density distributions in nanowires strongly nonuniform as the majority of the charge density is accumulated at...

Quasiparticle states in Dirac systems with complex impurity potentials are investigated. It is shown that an impurity site with loss leads to a nontrivial distribution of the local density of states (LDOS). While the real part of defect potential induces a well-pronounced peak in the density of states (DOS), the DOS is either weakly enhanced at sma...

We propose the concept of the time-independent correlators for the even- and odd-frequency pairing states that can be defined for both bosonic and fermionic quasiparticles. These correlators explicitly capture the existence of two distinct classes of pairing states and provide a direct probe of the hidden Berezinskii order. This concept is illustra...

We formulate a general framework for addressing both odd- and even-frequency superconductivity in Dirac semimetals and demonstrate that the odd-frequency or the Berezinskii pairing can naturally appear in these materials because of the chirality degree of freedom. We show that repulsive frequency-dependent interactions favor the Berezinskii pairing...

A nonlinear mechanism to generate a direct electric current by passing acoustic wave in inversion-symmetric Dirac and Weyl semimetals is proposed. It relies on pseudo-electromagnetic fields originating from dynamical sound-induced strains. Drawing on the similarity with the photogalvanic rectification, where a direct current is produced in a second...

The optical response of superconductors with odd-frequency Berezinskii pairing is studied. By using a simple model with a parabolic dispersion law and a nonmagnetic disorder, the spectral function, the electron density of states, and the optical conductivity are calculated for a few gap Ansätze. The spectral function and the electron density of sta...

The transport properties and electron states in cylinder nanowires of Dirac and Weyl semimetals are studied paying special attention to the structure and properties of the surface Fermi arcs. The latter make the electric charge and current density distributions in nanowires strongly nonuniform as the majority of the charge density is accumulated at...

We formulate a general framework for addressing both odd- and even-frequency superconductivity in Dirac semimetals and demonstrate that the odd-frequency or the Berezinskii pairing can naturally appear in these materials because of the chirality degree of freedom. We show that repulsive frequency-dependent interactions favor the Berezinskii pairing...

The optical response of superconductors with odd-frequency Berezinskii pairing is studied. By using a simple model with a parabolic dispersion law and a non-magnetic disorder, the spectral function, the electron density of states, and the optical conductivity are calculated for a few gap ansatzes. The spectral function and the electron density of s...

The hydrodynamic description of the Fermi arc surface states is proposed. In view of the strong suppression of scattering on impurities, the hydrodynamic regime for Fermi arc states should be, in principle, plausible. By using the kinetic theory, the Fermi arc hydrodynamics is derived and the corresponding effects on the bulk flow and surface colle...

The hydrodynamic description of the Fermi arc surface states is proposed. In view of the strong suppression of scattering on impurities, the hydrodynamic regime for Fermi arc states should be, in principle, plausible. By using the kinetic theory, the Fermi arc hydrodynamics is derived and the corresponding effects on the bulk flow and surface colle...

The effects of a strain-induced pseudomagnetic field on inter-node spin-triplet superconducting states in Weyl semimetals are studied by using the quasiclassical Eilenberger formalism. It is found that the Cooper pairing with spins parallel to the pseudomagnetic field has the lowest energy among the spin-triplet states and its gap does not depend o...

The effects of a strain-induced pseudomagnetic field on inter-node superconducting states in Weyl semimetals are studied by using the quasiclassical Eilenberger formalism. It is found that the spin-triplet superconducting state in which the spins of Cooper pairs are parallel to the pseudomagnetic field has the lowest energy and its gap does not dep...

The effects of strains on the low‐energy electronic properties of double‐Weyl phases are studied in solids and cold‐atom optical lattices. The principal finding is that deformations do not couple, in general, to the low‐energy effective Hamiltonian as a pseudoelectromagnetic gauge potential. The response of an optical lattice to strains is simpler,...

The motion of electron wave packets in the Dirac semimetals A3Bi (A= Na,K,Rb) is studied in a semiclassical approximation. Because of the twofold degeneracy of the Dirac points and a momentum-dependent gap term in the low-energy Hamiltonian, the associated Berry curvature is non-Abelian. In the presence of background electromagnetic fields, such a...

The spectrum of collective excitations in Weyl materials is studied by using a consistent hydrodynamics. The corresponding framework includes the vortical and chiral anomaly effects, as well as the dependence on the separation between the Weyl nodes in energy $b_0$ and momentum $\mathbf{b}$. The latter are introduced via the Chern--Simons contribut...

The effects of strains on the low-energy electronic properties of double-Weyl semimetal phases are studied in solids and cold-atom optical lattices. Our principal finding is that deformations do not couple, in general, to the low-energy effective Hamiltonian as a pseudoelectromagnetic gauge potential. The response of an optical lattice to strains i...

In this review we discuss a wide range of topological properties of electron quasiparticles in Dirac and Weyl semimetals. Their nontrivial topology is quantified by a monopole-like Berry curvature in the vicinity of Weyl nodes, as well as by the energy and momentum space separations between the nodes. The momentum separation, which is also known as...

The motion of electron wavepackets in the Dirac semimetals A$_3$Bi (A=Na,K,Rb) is studied in a semiclassical approximation. Because of the two-fold degeneracy of the Dirac points and a momentum-dependent gap term in the low-energy Hamiltonian, the associated Berry curvature is non-Abelian. In the presence of background electromagnetic fields, the l...

The nonlocal response of the chiral electron fluid in a semi-infinite Weyl semimetal slab with the electric current source and drain attached to its surface is studied by using the consistent hydrodynamic framework. It is found that the topological Chern-Simons terms lead to a spatial asymmetry of the electron flow and the electric field. Most rema...

The hydrodynamic flow of the chiral electron fluid in a Weyl semimetal slab of finite thickness is studied by using the consistent hydrodynamic theory. The latter includes viscous, anomalous, and vortical effects, as well as accounts for dynamical electromagnetism. The energy and momentum separations between the Weyl nodes are taken into account vi...

In this review we discuss a wide range of topological properties of electron quasiparticles in Dirac and Weyl semimetals. Their nontrivial topology is quantified by a monopole-like Berry curvature in the vicinity of Weyl nodes, as well as by the energy and momentum space separations between the nodes. The momentum separation, which is also known as...

The complete set of the Maxwell's and hydrodynamic equations for the chiral electrons in Weyl semimetals is presented. The formulation of the Euler equation takes into account the explicit breaking of the Galilean invariance by the ion lattice. The Chern-Simons (or Bardeen-Zumino) contributions to the electric current and charge densities are also...

The thermoelectric transport coefficients are calculated in a generic lattice model of multi-Weyl semimetals by using the Kubo's linear response theory. The contributions connected with the Berry curvature-induced electromagnetic orbital and heat magnetizations are systematically taken into account. It is shown that the thermoelectric transport is...

By using the exact solutions of the Weyl equation in a constant magnetic field, the equal-time Wigner function for magnetized chiral plasma is derived. It is found that the dependence of the Wigner function on the component of momentum along the magnetic field is asymmetric and is correlated with the fermion chirality. Such a dependence is principa...

It is proposed that strain-induced pseudomagnetic fields in Dirac and Weyl materials could be used as valley and chirality sensitive lenses for beams of Weyl quasiparticles. The study of the (pseudo)magnetic lenses is performed by using the eikonal approximation for describing the Weyl quasiparticles propagation in magnetic and strain-induced pseud...

For a generic lattice Hamiltonian of the electron states in Weyl materials, we calculate analytically the chiral charge and current (valley polarization) densities in the first order in background electromagnetic and strain-induced pseudoelectromagnetic fields. We find that the chiral response induced by the fields is not topologically protected. W...

For a generic lattice Hamiltonian of the electron states in Weyl semimetals, we calculate the electric charge and current densities in the first order in background electromagnetic and strain-induced pseudoelectromagnetic fields. We show that the resulting expressions for the densities contain contributions of two types. The contributions of the fi...

It is proposed that strain-induced pseudomagnetic fields in Weyl materials could be used as chirality sensitive lenses for beams of Weyl quasiparticles. The study of the (pseudo-)magnetic lenses is performed by using the eikonal approximation for describing the Weyl quasiparticles propagation in magnetic and strain-induced pseudomagnetic fields. An...

The consistent chiral kinetic theory accurate to the second order in electromagnetic and pseudoelectromagnetic fields is derived for a relativistic matter with two Weyl fermions. By making use of such a framework, the properties of longitudinal collective excitations, which include both chiral magnetic and chiral pseudomagnetic waves, are studied....

The existence of pseudomagnetic helicons is predicted for strained Weyl materials. The corresponding collective modes are similar to the usual helicons in metals in strong magnetic fields but can exist even without a magnetic field due to a strain-induced background pseudomagnetic field. The properties of both pseudomagnetic as well as magnetic hel...

The chiral plasmon modes of relativistic matter in background magnetic and strain-induced pseudomagnetic fields are studied in detail using the consistent chiral kinetic theory. The results reveal a number of anomalous features of these chiral magnetic and pseudomagnetic plasmons that could be used to identify them in experiment. In a system with n...

We argue that the correct definition of the electric current in the chiral kinetic theory for Weyl materials should include the Chern--Simons contribution that makes the theory consistent with the local conservation of the electric charge in electromagnetic and strain-induced pseudoelectromagnetic fields. By making use of such a kinetic theory, we...

The gap equations for the surface quasiparticle propagators in a slab of three-dimensional topological insulator in external electric and magnetic fields perpendicular to the slab surfaces are analyzed and solved. A different type of magnetic catalysis is revealed with the dynamical generation of both Haldane and Dirac gaps. Its characteristic feat...

The gap equations for the surface quasiparticle propagators in a slab of three-dimensional topological insulator in external electric and magnetic fields perpendicular to the slab surfaces are analyzed and solved. A new type of magnetic catalysis is revealed with the dynamical generation of both Haldane and Dirac gaps. Its characteristic feature ma...

By making use of a low-energy effective model of Weyl semimetals, we show that the Fermi arc transport is dissipative. The origin of the dissipation is the scattering of the surface Fermi arc states into the bulk of the semimetal. It is noticeable that corresponding scattering rate is nonzero and can be estimated even in a perturbative theory, alth...

We study the chiral separation and chiral magnetic effects in a slab of Dirac
semimetal of finite thickness, placed in a constant magnetic field
perpendicular to its surfaces. We utilize the Bogolyubov boundary conditions
with a large Dirac mass outside the slab. We find that a finite thickness of
the slab leads to a quantization of the axial curre...

The surface Fermi arc states in $Z_2$ Weyl semimetals $A_3 Bi$ (A=Na, K, Rb)
are studied by employing a continuum low-energy effective model. It is shown
that the surface Fermi arc states can be classified with respect to the
ud-parity symmetry. Because of the symmetry, the arcs come in mirror symmetric
pairs. The effects of symmetry breaking terms...

We demonstrate that the physical reason for the nontrivial topological properties of Dirac semimetals ${A}_{3}\mathrm{Bi}$ $(A=\mathrm{Na},\mathrm{K},\mathrm{Rb})$ is connected with a discrete symmetry of the low-energy effective Hamiltonian. By making use of this discrete symmetry, we argue that all electron states can be split into two separate s...

We demonstrate that the physical reason for nontrivial topological properties
of Dirac semimetals $\mathrm{A_3Bi}$
($\mathrm{A}=\mathrm{Na},\mathrm{K},\mathrm{Rb}$) is connected with a discrete
symmetry of the low-energy effective Hamiltonian. By making use of this
discrete symmetry, we argue that all electron states can be split into two
separate...