arXiv subjects

Marcin Matusiak

Publications and source records attributed to Marcin Matusiak.

At least 19 recordsLinked to original sources

arXiv2026

Observation of thermal Hall effect in diamond

Numerous insulators, including non-magnetic ones, have been unexpectedly found to display a finite thermal Hall signal, which has stimulated debate about its origin. Here, we report on a study of the thermal Hall effect in two diamond single crystals. The transverse thermal conductivity (kappa_xy) was found to peak at a temperature close to that at which the longitudinal thermal conductivity (kappa_xx) reaches its maximum. The measured kappa_xy, with an amplitude of 340 W/(m K) at B = 10 T, is the largest ever observed, while the kappa_xy/kappa_xx ratio follows the phenomenological trend identified in other insulators. Our observation implies the existence of an intrinsic thermal Hall effect in a generic phonon gas. We argue that the rough amplitude of both the thermal Hall angle and the thermal Hall resistivity can be accounted for by simple arguments invoking fundamental constants and quantum-mechanical constraints on solid state cohesion.

cond-mat.mtrl-sci↗

arXiv2026

Transverse and Longitudinal Magnetothermopower Promoted by Ambipolar Effect in Half-Heusler Topological Materials

Topologically trivial and non-trivial semimetals with a high degree of carrier compensation are well known for demonstrating large transverse magnetothermopower ($S_{yx}$). However, in such systems, the longitudinal magnetothermopower ($S_{xx}$) is typically suppressed due to nearly perfect electron-hole compensation. Here, we show that the half-Heusler topological semimetal DyPtBi exhibits simultaneously large $S_{xx}$ and $S_{yx}$ magnetothermopowers, defying this conventional trade-off. In $B=14$\,T, thermopower of DyPtBi reaches peak values of $S_{xx}=131\,\mu\rm{V/K}$ at $T=149$\,K and $S_{yx}=-297\,\mu\rm{V/K}$ at $T=200$\,K, and transverse component remains significantly large even at $290$\,K ($S_{yx}=-213\,\mu\rm{V/K}$). Remarkably, at $T=290$\,K and in relatively weak magnetic field of $1$\,T, both relevant for practical applications, DyPtBi shows $S_{yx}=-18\,\mu\rm{V/K}$, which is one of the largest values reported under such conditions. The large transverse thermopower originates from an ambipolar effect associated with thermal excitation occurring in zero-gap semiconductors. Due to the imperfect electron-hole compensation, an intrinsic asymmetry between hole- and electron-type carriers enables pronounced values of both $S_{xx}$ and $S_{yx}$, resulting in high effective thermopower ($S_{xx}+|S_{yx}|=379\,\mu\rm{V/K}$) in DyPtBi at 200\,K. A comparative analysis with DyPdBi, another half-Heusler material that demonstrates large $S_{xx}=123\,\mu\rm{V/K}$ but small $S_{yx}=-16\,\mu\rm{V/K}$ (both values obtained at $T=293$\,K and $B=14$\,T), highlights the critical role of band structure and compensation tuning. These findings underscore the potential of chemical doping and band engineering in rare-earth-based half-Heusler materials for optimizing both transverse and longitudinal thermoelectric properties.

cond-mat.mtrl-sci↗

arXiv2025

Anisotropic suppression of the phononic thermal conductivity by magnetic field in SmAlSi

We report the thermal and electrical conductivity data for the magnetic Weyl semimetal SmAlSi measured in a magnetic field (B) with two different orientations. In one case, B was applied perpendicular to the heat or charge current, in the other they were parallel. For both configurations, the magnetic field affects the magnetic structure identically as B is always parallel to the equivalent tetragonal axis. Our results indicate that phonon heat transport in response to the magnetic field exhibits strong anisotropy at low temperature: it appears to be independent of B in the perpendicular configuration but is strongly suppressed in the parallel configuration. Understanding this unusual behaviour can lead to designing better materials for thermoelectricity or directional heat switches.

cond-mat.str-el↗

arXiv2024

Quantum transport properties of the topological Dirac Semimetal $α$-Sn

We report measurements of the electrical resistivity ($ρ$) and thermoelectric power (S) in a thin film of strained single-crystalline $α$-Sn grown by molecular beam epitaxy on an insulating substrate. The temperature (T) dependence of the resistivity of $α$-Sn can be divided into two regions:below T* $\approx$ 135 K $ρ$(T) shows a metallic-like behaviour, while above this temperature an increasing contribution from thermally excited holes to electrical transport is observed. However, it is still dominated by highly mobile electrons, resulting in a negative sign of the Seebeck coefficient above T = 47 K. In the presence of the magnetic field (B) applied along an electric field or thermal gradient, we note a negative magnetoresistance or a negative slope of S(B), respectively. The theoretical prediction for the former (calculated using density functional theory) agrees well with the experiment. However, these characteristics quickly disappear when the magnetic field is deviated from an orientation parallel to the electrical field or the thermal gradient. We indicate that the behaviour of the electrical resistivity and thermoelectric power can be explained in terms of the chiral current arising from the topologically non-trivial electronic structure of $α$-Sn. Its decay at high temperature is a consequence of the decreasing ratio between the intervalley Weyl relaxation time to the Drude scattering time.

cond-mat.str-el↗

arXiv2023

Gravitational anomaly in the ferrimagnetic topological Weyl semimetal NdAlSi

Quantum anomalies are the breakdowns of classical conservation laws that occur in quantum-field theory description of a physical system. They appear in relativistic field theories of chiral fermions and are expected to lead to anomalous transport properties in Weyl semimetals. This includes a chiral anomaly, which is a violation of the chiral current conservation that takes place when a Weyl semimetal is subjected to parallel electric and magnetic fields. A charge pumping between Weyl points of opposite chirality causes the chiral magnetic effect that has been extensively studied with electrical transport. On the other hand, if the thermal gradient, instead of the electrical field, is applied along the magnetic field, then as a consequence of the gravitational (also called the thermal chiral) anomaly an energy pumping occurs within a pair of Weyl cones. As a result, this is expected to generate anomalous heat current contributing to the thermal conductivity. We report an increase of both the magneto-electric and magneto-thermal conductivities in quasi-classical regime of the magnetic Weyl semimetal NdAlSi. Our work also shows that the anomalous electric and heat currents, which occur due to the chiral magnetic effect and gravitational anomalies respectively, are still linked by a 170 years old relation called the Wiedemann-Franz law.

cond-mat.mes-hall↗

arXiv2023

Sign change of the anomalous Hall effect and the anomalous Nernst effect in Weyl semimetal CeAlSi

We report the anomalous Hall effect (AHE) and the anomalous Nernst effect (ANE) data for the non-collinear Weyl semimetal CeAlSi. The anomalous Hall conductivity (σ_ij^A) was measured for two different orientations of the magnetic field (B), namely σ_yz^A for B II a and σ_xy^A for B II c, where a and c denote the crystallographic axes. We find that σ_xy^A and σ_yz^A are of opposite sign and both are large below the Curie temperature (T_C). In the paramagnetic phase, σ_xy^A raises even more and goes through a maximum at T ~ 170 K, whereas the absolute value of σ_yz^A decreases with increasing temperature. The origin of the sign difference between σ_xy^A and σ_yz^A was attributed to the reconstruction of the band structure under the variation of the spin orientation. Further, in a system where humps in the AHE are present and scalar spin chirality is zero, we show that the k-space topology plays an important role to determine the transport properties at both low and high temperatures. We also observed the anomalous contribution in the Nernst conductivity (α_xy^A) measured for B II c. α_xy^A/T turns out to be sizeable in the magnetic phase and above T_C slowly decreases with temperature. We were able to recreate the temperature dependences of σ_xy^A and α_xy^A/T in the paramagnetic phase using a single band toy-model assuming a non-zero Berry curvature in the vicinity of the Weyl node. A decisive factor appears to be a small energy distance between the Fermi level and a Weyl point.

cond-mat.str-el↗

arXiv2022

Temperature driven spin-zero effect in TaAs$_2$

The electrical and thermo-electrical transport effects of the TaAs$_2$ semimetal were measured in a magnetic field applied along [-2 0 1] direction. The resulting field dependences of the resistivity as well as the Hall, Seebeck and Nernst coefficient below T ~ 100 K can be satisfactory described within the two-band model consisting of the electron and hole pockets. At low temperature all the measured effects exhibit significant contribution from quantum oscillations. The fast Fourier transform (FFT) of the oscillatory Nernst signal shows two fundamental frequencies, Fa = 105 T and Fb = 221 T, and the second harmonic of the latter (F2b = 442 T). The ratio between FFT amplitudes of Fb and F2b changes with temperature in an unusual way, indicating that we observe the spin-zero effect caused by temperature change. This is likely related to substantial temperature dependence of the Lande g-factor, which in turn can result from non-parabolic energy dispersion or temperature evolution of the spin-orbit coupling.

cond-mat.mtrl-sci↗

arXiv2022

Severe violation of the Wiedemann-Franz law in quantum oscillations of NbP

The thermal conductivity (k) of the Weyl semimetal NbP was studied with the thermal gradient and magnetic field applied parallel to [0 0 1] direction. At low temperatures k(B) exhibits large quantum oscillations with frequencies matching two of several determined from the Shubnikov - de Haas effect measured on the same sample with analogous electrical current and magnetic field orientation. Both frequencies found in k(B) originate from the electron pocket enclosing a pair of Weyl nodes. The amplitude of the oscillatory component of the thermal conductivity turns out to be two orders of magnitude larger than the corresponding value calculated from the electrical conductivity using the Wiedemann - Franz law. Analysis of possible sources of this discrepancy indicates the chiral zero sound effect as a potential cause of its appearance.

cond-mat.str-el↗

arXiv2019

Thermoelectric signature of the nematic phase in iron-based superconductor

Studies of the copper-based superconductors demonstrate how their phase diagram becomes more complex as experimental probes improve, able to distinguish among subtly different electronic phases. One of those phases, nematicity, has become the matter of great interest also in the iron-based superconductors, where it is detected deep in the tetragonal state. Here we present the evolution of the in-plane Nernst effect anisotropy in the strain detwinned Ca(Fe1-xCox)2As2 single crystals, whose behaviour can be explained within the approach developed to describe the nematic order parameter in liquid crystals [1,2]. Furthermore, the employed method turns out to be universally applicable to data from other superconductors: Ba(Fe1-xCox)2As2 [3] as well as YBa2Cu3Oy [4]. We conclude the observed broken rotational symmetry of the electronic system is a consequence of the emerging thermodynamic electronic nematic order at a temperature much higher than onset of the magnetic and structural transitions.

cond-mat.supr-con↗

arXiv2018

Thermoelectric anisotropy in Ba(Fe1-xCox)2As2 iron-based superconductor

We report the in-plane anisotropy of the Seebeck and Nernst coefficients as well as of the electrical resistivity determined for the series of the strain-detwinned single crystals of Ba(Fe1-xCox)2As2. Two underdoped samples (x = 0.024, 0.045) exhibiting the transition from the tetragonal paramagnetic phase to the orthorhombic spin density wave (SDW) phase (at Ttr = 100 and 60 K, respectively) show an onset of the Nernst anisotropy at temperatures above 200 K, which is significantly higher than Ttr. In the optimally doped sample (x = 0.06) the transport properties also appear to be in-plane anisotropic below T = 120 K, despite the fact that this particular composition does not show any evidence of long-range magnetic order. However, the anisotropy observed in the optimally doped crystal is rather small and for the Seebeck and Nernst coefficients the difference between values measured along and across the uniaxial strain has opposite sign to those observed for underdoped crystals with x = 0.024 and 0.045. For these two samples, insensitivity of the Nernst anisotropy to the SDW transition suggests that the nematicity might be of other than magnetic origin.

cond-mat.supr-con↗

arXiv2018

Anisotropy of the Seebeck and Nernst coefficients in parent compounds of the iron-based superconductors

In-plane longitudinal and transverse thermoelectric phenomena in two parent compounds of iron-based superconductors are studied. Namely, the Seebeck (S) and Nernst (n) coefficients were measured in the temperature range 10 - 300 K for BaFe2As2 and CaFe2As2 single crystals that were detwinned in-situ. The thermoelectric response shows sizeable anisotropy in the spin density wave state (SDW) for both compounds, while some dissimilarities in the vicinity of the SDW transition can be attributed to the different nature of the phase change in BaFe2As2 and CaFe2As2. Temperature dependences of S and n can be described within a two-band model that contains a contribution from highly mobile, probably Dirac, electrons. The Dirac band seems to be rather isotropic, whereas most of the anisotropy in the transport phenomena could be attributed to "regular" hole-like charge carriers. We also observe that the off-diagonal element of the Peltier tensor axy is not the same for the a and b orthorhombic axes, which indicates that the widely used Mott formula is not applicable to the SDW state of iron-based superconductors.

cond-mat.supr-con↗

arXiv2017

Thermoelectric quantum oscillations in ZrSiS

Topological semimetals are systems in which the conduction and the valence bands cross each other and this crossing is protected by topological constraints. These materials provide an intriguing test of fundamental theory and their exceptional physical properties promise a wide range of possible applications. Here we report a study of the thermoelectric power (S) for a single crystal of ZrSiS that is believed to be a topological nodal-line semimetal. We detect multiple quantum oscillations in the magnetic field dependence of S that are still visible at temperature as high as T = 100 K. Two of these oscillation frequencies are shown to arise from 3D and 2D bands, each with linear dispersion and the additional Berry phase expected theoretically.

cond-mat.str-el↗

arXiv2016

Multiband thermal transport in the iron-based superconductor Ba1 xKxFe2As2

We present results of precise measurements of the thermal and electrical transport in the optimally- and over-doped Ba1-xKxFe2As2 single crystals (x = 0.35, 0.55, 0.88) and compare them to the previously reported data on Ba(Fe1-yCoy)2As2. A contraction of the electron pocket is observed upon substitution potassium for barium, but even at the extreme doping (x = 0.88) there is still a noticeable contribution from negative charge carriers to the electronic transport. The size of the electron pocket in all K-doped samples is small enough to cause a significant enhancement of the respective Hall-Lorenz number. Another observed characteristic is the emergence of a maximum in the transverse thermal conductivity below the superconducting critical temperature of the optimally- (x = 0.35) and slightly over-doped (x = 0.55) samples. The evolution of this anomaly from the optimally electron-doped Ba(Fe0.94Co0.06)2As2 to hole-overdoped Ba0.45K0.55Fe2As2 suggests formation of a uniform superconducting gap on the electron pocket in the former and regions of a depressed gap on the hole-pocket in the latter.

cond-mat.supr-con↗

arXiv2015

Violation of the Wiedemann-Franz law as an evidence of the pseudogap in the iron-based superconductor Ba(Fe1-xCox)2As2

Longitudinal and transverse transport coefficients of the Ba(Fe1-xCox)2As2 single crystals with x = 0, 0.045, 0.06 and 0.244 were measured in the temperature range 1.4 - 300 K and in magnetic fields up to 12.5 T. The resulting data were used to determine the temperature dependence of the Hall Lorenz number (Lxy) and its evolution with doping. Lxy is defined by the electronic contributions to the thermal and electrical conductivities and it is found to differ from its canonical behavior. This shows the emergence of a pseudogap in samples at intermediate doping.

cond-mat.supr-con↗

arXiv2012

Magnetothermoelectric effects in Fe{1+d}Te{1-x}Se{x}

We report resistivity as well as the Hall, Seebeck and Nernst coefficients data for Fe{1+d}Te{1-x}Se{x} single crystals with x = 0, 0.38, and 0.40. In the parent compound Fe{1.04}Te we observe at Tn = 61 K a sudden change of all quantities studied, which can be ascribed to the Fermi surface reconstruction due to onset of the antiferromagnetic order. Two very closely doped samples: Fe{1.01}Te{0.62}Se{0.38} (Se38) and Fe{1.01}Te{0.60}Se{0.40} (Se40) are superconductors with Tc = 13.4 K and 13.9 K, respectively. There are no evident magnetic transitions in either Se38 or Se40. Properties of these two single crystals are almost identical at high temperatures, but start to diverge below T ~ 80 K. Perhaps we see the onset of scattering that might be a related to changes in short range magnetic correlations caused by selenium doping.

cond-mat.supr-con↗

arXiv2012

Quantum criticality in Ce2PdIn8: thermoelectric study

We report the Nernst effect (v) and thermoelectric power (S) data for the Ce2PdIn8 heavy-fermion compound. Both S and v behave anomalously at low temperatures: the thermopower shows a Kondo-like maximum at T = 37 K, while the Nernst coefficient becomes greatly enhanced and field dependent below T ~ 30 K. In the zero-T limit S/T and v/T diverge logarithmically, what is related to occurrence of the quantum critical point (QCP). Presented results suggest that the antiferromagnetic spin-density-wave scenario may be applicable to QCP in Ce2PdIn8.

cond-mat.str-el↗

arXiv2012

Anomalous magnetotransport in the heavy-fermion superconductor Ce2PdIn8

The normal state behavior in the heavy-fermion superconductor Ce2PdIn8 has been probed by means of Hall coefficient (RH) and transverse magnetoresistivity (MR) measurements. The results indicate the predominance of contributions from antiferromagnetic spin fluctuations at low temperatures. Anomalous non-Fermi-liquid-like features, observed below 8 K in both RH(T) and MR(T), are related to underlying quantum critical point, evidenced before in the specific heat and the electrical resistivity data. The magnetotransport in Ce2PdIn8 is shown to exhibit specific types of scaling that may appear universal for similar systems at the verge of magnetic instability.

cond-mat.str-el↗

arXiv2011

Isothermal magnetocaloric effect in the vicinity of the Lifshitz point in Mn_{0.9}Co_{0.1}P

The magnetic field - temperature (B - T) phase diagram of the Mn0.9Co0.1P single crystal is studied in the vicinity of the Lifshitz point by means of isothermal magnetocaloric coefficient (Mt) and AC susceptibility measurements. Results confirm previously reported shape of the B - T phase diagram and locations of characteristic temperatures and fields. At the Curie temperature (Tc) the critical exponent w, which describes a singularity of Mt as a function of magnetic field (Mt \propto B^-w), is estimated for B parallel to the easy axis to be equal to w \approx 0.35. Below Tc an evidence of a new enigmatic phase, reported already for pure MnP, is found in susceptibility data also for Mn0.9Co0.1P. However, the range of existence of this phase is significantly larger here, than in MnP. At the Lifshitz point there is observed a sharp peak in the imaginary part of the magnetic susceptibility. A phenomenological theory is introduced to describe the field dependence of the critical lines from the disordered phase (paramagnetic) to ordered phases (ferromagnetic and modulated). The temperature and field dependences of the magnetocaloric coefficient and susceptibility are also calculated within the same framework.

cond-mat.stat-mech↗