arXiv subjects

Karol I. Wysokinski

Publications and source records attributed to Karol I. Wysokinski.

At least 19 recordsLinked to original sources

arXiv2026

Conformal anomaly transport induced by dark photon

We have considered the problem of the influence of inhomogeneity of gravitational field on transport effects predicted by the field theory describing massless Dirac fermions in the Maxwell and dark matter background. As a model of dark sector one takes into account dark photon model, where the hidden sector is described by the auxiliary U(1)-gauge field coupled to the visible sector. Elaborating the model we restrict our considerations to the case when Weyl type conformal transformation slightly differs from the Minkowski spacetime. This assumption simplifies the calculations and enables us not to use complicated methods of the quantum field theory in the curved background. The resulting currents stemming both from visible and dark sectors are proportional to the adequate beta functions appearing in the elaborated systems. For charge-less dark sector we predict corrections to the scale conductivities in both sectors: linear in α in the dark sector and quadratic in the visible one.

gr-qc↗

arXiv2023

Charge transport in chiral solids as a possible tool in search of dark matter signals

As the existing techniques to directly detect dark matter particles in laboratory experiments continue to produce negative signals, the research community considers novel approaches including those relying on condensed matter systems with non-trivial quantum properties. For example, finding signatures of dark matter in transport characteristics of solids would be an important step on the road to detect this illusive component of the mass of our Universe. As a first step in this direction we have recently derived the modified kinetic equation taking into account two coupled $U(1)$-gauge fields, one being the standard Maxwell electromagnetic field and other corresponding to the dark sector. The resulting Boltzmann kinetic equation is modified by the Berry curvature which couples to both visible and dark sector gauge fields. The linear and nonlinear longitudinal and/or Hall currents in topological matter may signal the existence of dark particle induced electromagnetic fields. The usage of appropriately designed resonant cavity to enhance the electric field may help to reach the goal. The conservative estimates show that the technique should have the sensitivity of the order of $10^{-9}$ or better and may help to partially fill the gap between XENON1T and haloscope experiments.

hep-th↗

arXiv2023

Chiral kinetic theory in the presence of dark photon

Finding signatures of dark matter in transport characteristics of solids would be an important step on the road to detect this illusive component of the mass of our Universe. This is especially important and timely as the experiments designed to directly detect dark matter particles continue to provide negative results. As a first step in this direction we consider topologically non-trivial Weyl or Dirac semimetals and derive the modified kinetic equation taking into account two coupled $U(1)$-gauge fields, one being the standard Maxwell electromagnetic field and other corresponding to the dark sector. The resulting Boltzmann kinetic equation is modified by the Berry curvature which couples to both visible and dark sector gauge fields. It was revealed that the dark sector induces modifications of transport coefficients due to the appearance of coupling constant between gauge fields and dark sector magnetic field.

hep-th↗

arXiv2020

Conductivity bound of the strongly interacting and disordered graphene from gauge/gravity duality

The carriers in graphene tuned close to the Dirac point envisage signatures of the strongly interacting fluid and are subject to hydrodynamic description. The important question is whether strong disorder induces the metal-insulator transition in this two-dimensional material. The bound on the conductivity tensor found earlier within the single current description, implies that the system does not feature metal-insulator transition. The linear spectrum of the graphene imposes the phase-space constraints and calls for the two-current description of interacting electron and hole liquids. Based on the gauge/gravity correspondence, using the linear response of the black brane with broken translation symmetry in Einstein-Maxwell gravity with the auxiliary U(1)-gauge field, responsible for the second current, we have calculated the lower bound of the DC-conductivity in holographic model of graphene. The calculations show that the bound on the conductivity depends on the coupling between both U(1) fields and for a physically justified range of parameters it departs only weakly from the value found for a model with the single U(1) field.

hep-th↗

arXiv2019

Magnetotransport of Weyl semimetals with $\mathbb{Z}_2$ topological charge and chiral anomaly

We calculate the magnetoconductivity of the Weyl semimetal with $\mathbb{Z}_2$ symmetry and chiral anomaly utilizing the recently developed hydrodynamic theory. The system in question will be influenced by magnetic fields connected with ordinary Maxwell and the second $U(1)$-gauge field, which is responsible for anomalous topological charge. The presence of chiral anomaly and $\mathbb{Z}_2$ anomalous charge endow the system with new transport coefficients. We start with the linear perturbations of the hydrodynamic equations and calculate the magnetoconductivity of this system. The holographic approach in the probe limit is implemented to obtain the explicit dependence of the longitudinal magnetoconductivities on the magnetic fields.

hep-th↗

arXiv2018

Hydrodynamics of topological Dirac semi-metals with chiral and $\mathbb{Z}_2$ anomalies

We consider the hydrodynamical model of topological Dirac semi-metal possessing two Dirac nodes separated in momentum space along a rotation axis. It has been argued that the system in question, except the chiral anomaly, is endowed with the other one $\mathbb{Z}_2$. In order to model such a system we introduce two $U(1)$-gauge fields. The presence of the additional $\mathbb{Z}_2$ anomaly leads to the non-trivial modifications of hydrodynamical equations and to the appearance of new kinetic coefficients bounded with the vorticity and the magnetic parts of Maxwell and auxiliary $U(1)$-gauge fields.

hep-th↗

arXiv2017

Viscosity bound for anisotropic superfluids with dark matter sector

The shear viscosity to the entropy density ratio $η/s$ of the anisotropic superfluid has been calculated by means of the gauge/gravity duality in the presence of the {\it dark matter} sector. The {\it dark matter} has been described by the Yang-Mills field analogous to the one describing visible matter sector and it is assumed to interact with the visible field with coupling constant $α$. Close to the superfluid transition temperature ($T_c$) the analytical solution has been given up to the leading order in a symmetry breaking parameter and the ratio of the gravitational constant and Yang-Mils coupling. The tensor element of ratio $η/s$ remains unaffected by the {\it dark matter} for the viscosity tensor in the plane perpendicular to the symmetry breaking direction (here $yz$). The temperature dependence and the linear correction in $(1-α)$ in the plane containing this direction (here $xy$) was also revealed. The correction linearly vanishes for temperature tending to the critical one $T\rightarrow T_c$.

hep-th↗

arXiv2016

Condensate flow in holographic models in the presence of dark matter

Holographic model of a three-dimensional current carrying superconductor or superfluid with {\it dark matter} sector described by the additional $U(1)$-gauge field coupled to the ordinary Maxwell one, has been studied in the probe limit. We investigated analytically by the Sturm-Liouville variational method, the holographic s-wave and p-wave models in the background of the AdS soliton as well as five-dimensional AdS black hole spacetimes. The two models of p-wave superfluids were considered, the so called $SU(2)$ and the Maxwell-vector. Special attention has been paid to the dependence of the critical chemical potential and critical transition temperature on the velocity of the condensate and {\it dark matter} parameters. The current $J$ in holographic three-dimensional superconductor studied here, shows the linear dependence on $T_c-T$ for both s and p-wave symmetry. This is in a significant contrast with the previously obtained results for two-dimensional superconductors, which reveal the $(T-T_c)^{3/2}$ temperature dependence. The coupling constant $α$, as well as, chemical potential $μ_D$ and the velocity $S_D$ of the {\it dark matter}, affect the critical chemical potential of the p-wave holographic $SU(2)$ system. On the other hand, $α$, {\it dark matter} velocity $S_D$ and density $ρ_D$ determine the actual value of the transition temperature of the same superconductor/superfluid set up. However, the {\it dark matter} does not affect the value of the current.

hep-th↗

arXiv2016

P-wave holographic superconductor/insulator phase transitions affected by dark matter sector

The holographic approach to building the p-wave superconductors results in three different models: the Maxwell-vector, the SU(2) Yang-Mills and the helical. In the probe limit approximation, we analytically examine the properties of the first two models in the theory with {\it dark matter} sector. It turns out that the effect of {\it dark matter} on the Maxwell-vector p-wave model is the same as on the s-wave superconductor studied earlier. For the non-Abelian model we study the phase transitions between p-wave holographic insulator/superconductor and metal/superconductor. Studies of marginally stable modes in the theory under consideration allow us to determine features of p-wave holographic droplet in a constant magnetic field. The dependence of the superconducting transition temperature on the coupling constant $α$ to the {\it dark matter} sector is affected by the {\it dark matter} density $ρ_D$. For $ρ_D>ρ$ the transition temperature is a decreasing function of $α$. The critical chemical potential $μ_c$ for the quantum phase transition between insulator and metal depends on the chemical potential of dark matter $μ_D$ and for $μ_D=0$ is a decreasing function of $α$.

hep-th↗

arXiv2016

Local and non-local thermopowers in three-terminal nanostructures

The thermoelectric effects in three-terminal structures with a quantum dot are considered. We propose the experimentally consistent protocol for determination of the transport coefficients in terms of the local and non-local conductances and thermopowers that can be measured in two steps, applying the `four probe technique'. This proposal is compared with other approaches discussed so far in the literature. As an example we study in detail the thermopower induced by the superconducting electrode in a subgap regime which might be useful for analysis of novel hybrid devices.

cond-mat.mes-hall↗

arXiv2016

Holographic superconductivity in the presence of dark matter: basic issues

The holographic approach to study strongly coupled superconductors in the presence of dark matter is reviewed. We discuss the influence of dark matter on the superconducting transition temperature of both s-wave and p-wave holographic superconductors. The upper critical field, coherence length, penetration depth of holographic superconductors as well as the metal-insulator transitions have also been analysed. Issues related to the validity of AdS/CFT correspondence for the description of superconductors studied in the laboratory and possible experiments directed towards the detection of dark matter are discussed. In doing so we shall compare our assumptions and assertions with those generally accepted in the elementary particle experiments aimed at the detection of dark matter particles.

physics.gen-ph↗

arXiv2016

Optimization of a three-terminal non-linear heat nano-engine

Charge and heat transport in nano-structures is dominated by non-equilibrium effects which strongly influence their behaviour. These effects are studied in a setup consisting of three external leads, one of which is considered as a heat reservoir and is tunnel-coupled to two cold electrodes via two independently controlled quantum dots. The energy flow from the hot electrode together with energy filtering provided by quantum dots leads to a voltage bias between the cold electrodes. The heat and charge currents in the device effectively flow in mutually perpendicular directions, allowing for their independent control. The non-equilibrium screening changes the values of the system parameters needed for its optimal performance but leaves the maximal output power and efficiency unchanged. Our results are important from the theoretical point of view as well as for the practical implementation and the control of the proposed heat engine.

cond-mat.mes-hall↗

arXiv2015

Holographic vortices in the presence of dark matter sector

The {\it dark matter} seem to be an inevitable ingredient of the total matter configuration in the Universe and the knowledge how the {\it dark matter} affects the properties of superconductors is of vital importance for the experiments aimed at its direct detection. The homogeneous magnetic field acting perpendicularly to the surface of (2+1) dimensional s-wave holographic superconductor in the theory with {\it dark matter} sector has been modeled by the additional $U(1)$-gauge field representing dark matter and coupled to the Maxwell one. As expected the free energy for the vortex configuration turns out to be negative. Importantly its value is lower in the presence of {\it dark matter} sector. This feature can explain why in the Early Universe first the web of {\it dark matter} appeared and next on these gratings the ordinary matter forming cluster of galaxies has formed.

hep-th↗

arXiv2013

Interplay between direct and crossed Andreev reflections in hybrid nano-structures

The interplay between various many body effects in a quantum dot attached to two normal and one superconducting lead is considered in the limit of large superconducting gap. By the proximity effect the superconducting lead induces pairing correlations on the quantum dot. In the subgap region one observes the anomalous tunneling via direct and crossed Andreev scattering, whereas the usual single particle electronic transfer is suppressed. The interactions of electrons on the dot leading to such phenomena as the Coulomb blockade and the Kondo effect severely modify the currents flowing in the system. In particular: (i) they prevent the existence of the negative differential conductance observed for non-interacting quantum dot over the whole range of voltages, (ii) affect the distribution of the currents as function of the applied voltage and (iii) lead to the appearance of additional low bias feature due to the formation of the Abrikosov-Suhl resonance. The non-local correlations in the Coulomb blockade regime are most pronounced for the particle-hole symmetric dot and thus can be easily tuned by means of gate voltage. They are observed even in the Kondo regime and dominate the behavior close to the Abrikosov-Suhl resonance showing convincingly that Kondo correlations do not destroy subtle entanglement between electrons.

cond-mat.mes-hall↗

arXiv2013

The Kerr rotation in the unconventional superconductor Sr$_2$RuO$_4$

The interpretation of Kerr rotation measurements in the superconducting phase of Sr$_2$RuO$_4$ is a controversial topic. Both intrinsic and extrinsic mechanisms have been proposed, and it has been argued that the intrinsic response vanishes by symmetry. We focus on the intrinsic contribution and clarify several conflicting results in the literature. On the basis of symmetry considerations and detailed calculations we show that the intrinsic Kerr signal is not forbidden in a general multi- band system but has a rich structure in the near infrared regime. We distinguish different optical transitions determined by the superconducting gap (far infrared) and the inter orbital coupling of the normal state (near infrared). We argue that the low frequency transitions do not contribute to the Hall conductivity while only the inter-orbital transitions in the near infrared regime contribute. Finally, we discuss the difficulties to connect the calculations for the optical Hall conductivity to the experimental measurement of the Kerr angle. We will compare different approximations which might lead to conflicting results.

cond-mat.supr-con↗

arXiv2012

Intrinsic optical dichroism in the chiral superconducting state of Sr$_{2}$RuO$_{4}$

We present an analysis of the Hall conductivity $σ_{xy}(ω, T)$ in time reversal symmetry breaking states of exotic superconductors. We find that the dichroic signal is non-zero in systems with inter-band order parameters. This new intrinsic mechanism may explain the Kerr effect observed in strontium ruthenate and possibly other superconductors. We predict coherence factor effects in the temperature dependence of the imaginary part of the ac Hall conductivity $ Imσ_{xy}(ω, T)$, which can be tested experimentally.

cond-mat.supr-con↗

arXiv2011

Remarks on the first hundred years of superconductivity

On the occasion of centenary of superconductivity discovery I recall some facts from the first period and attempts to understand the phenomenon. It turns out that most famous physicists of the first half of XX century have tried to solve the puzzle. Bardeen, Cooper and Schrieffer succeeded in 1957. The BCS theory successfully described all known facts and offered new predictions, which soon have been confirmed experimentally contributing to the widespread acceptance of the theory. It have found applications in nuclear physics, theory of neutron stars and cold atomic gases. The discoveries of new superconductors in the last thirty years show that simple BCS model is not enough to understand new unconventional superconductors. The studies of superconductors develop vividly and still fascinate new generations of physicists working in such diverse fields as material science and string theory.

physics.hist-ph↗

arXiv2009

Interorbital pair scattering in clean and impure superconductors

The calculations of the local and global properties of two band superconductors have been presented with particular attention to the role of the inter-orbital scattering of pairs. The properties of such superconductors are very different from a single band or typical two band systems with dominant intra-band pairing interactions. The role of Van Hove singularity in one of the bands on the properties of intra-band clean superconductor has been discussed. It leads to marked increase of superconducting transition temperature in the weak coupling limit. We study the inhomogeneous systems in which the characteristics change from place to place by solving the Bogolubov-de Gennes equations for small clusters. The suppression of the superconducting order parameter by the single impurity scattering the fermions between bands is contrasted with that due to intra-band impurity scattering. The results obtained for impure systems have been shown as a maps of local density of states, the order parameter and gap function. They can be directly compared with STM spectra of the real material.

cond-mat.supr-con↗