arXiv subjects

Gabriel Kuderowicz

Publications and source records attributed to Gabriel Kuderowicz.

6 recordsLinked to original sources

arXiv2026

Multiband superconductivity in the kagome-lattice superconductor Re2Zr

We present a first-principles investigation of the electronic structure, lattice dynamics, electron-phonon coupling, and superconducting properties of the hexagonal kagome-lattice compound Re$_2$Zr, in which time-reversal symmetry breaking and unconventional pairing have recently been proposed. We examine whether superconductivity in Re$_2$Zr can be explained within a conventional phonon-mediated framework by performing fully ab initio calculations within the density functional theory for superconductors. The electronic structure is characterized by a mixture of seven two- and three-dimensional Fermi surface sheets, giving rise to multiband superconductivity with many overlapping superconducting gaps. A spin-orbit-induced van Hove singularity is identified in the density of states near $E_F$. The electron-phonon interaction is moderately strong, with a coupling constant $\lambda \simeq 0.88$. Superconducting gap calculations reveal significant anisotropy and a broad distribution of gap values across different Fermi surface sheets. Spin fluctuations introduce additional depairing effects and reduce the critical temperature from 7.7 K to 6.4 K, in excellent agreement with the experimental value of 6.65 K. Taken together, our results show that the superconducting energy scale in Re$_2$Zr can be quantitatively reproduced within a conventional phonon-mediated framework, while the resulting state exhibits pronounced multiband and anisotropic gap structure. The origin of the experimentally suggested time-reversal symmetry breaking, however, remains an open question.

cond-mat.supr-con↗

arXiv2023

Strong-coupling superconductivity of the Heusler-type compound ScAu2Al: Ab-initio studies

The ScAu$_2$Al superconducting Heusler-type compound was recently characterized to have the highest critical temperature of $T_c = 5.12$ K and the strongest electron-phonon coupling among the Heusler family. In this work, the electronic structure, phonons, electron-phonon coupling, and superconductivity of ScAu$_2$Al are studied using \textit{ab initio} calculations. The spin-orbit coupling significantly changes the electronic structure removing the van Hove singularity from the vicinity of the Fermi level. In the phonon spectrum, low frequency acoustic modes, additionally softened by the spin-orbit interaction, strongly couple with electrons, leading to the electron-phonon coupling constant $λ=1.25$, a record high among Heuslers. The density functional theory for superconductors is then used to analyze superconducting {state in this two-band superconductor}. The effect of spin fluctuations (SF) on superconductivity is also analyzed. The calculated critical temperatures of $T_c = 5.16$ K (4.79 K with SF) agree very well with the experiment, confirming the electron-phonon mechanism of superconductivity and showing a weak spin-fluctuations effect. The superconducting gaps formed on two Fermi surface sheets exhibit moderate anisotropy. Their magnitudes confirm the strong coupling regime, as the reduced average values are $2Δ_1/k_BT_c \simeq 4.1$ and $2Δ_2/k_BT_c \simeq 4.3$. Anisotropy of the gaps and large spread in their values significantly affect the calculated quasiparticle density of states.

cond-mat.supr-con↗

arXiv2022

Pressure effects on the electronic structure, phonons, and superconductivity of noncentrosymmetric ThCoC2

The electronic structure, phonons, electron-phonon coupling, and superconductivity are theoretically studied in noncentrosymmetric superconductor ThCoC$_2$ as a function of pressure, in the pressure range 0 - 20 GPa. We found that the electronic band splitting induced by the spin-orbit coupling is enhanced under pressure. In spite of the overall stiffening of the crystal lattice, the electron-phonon coupling constant $λ$ increases with pressure, from 0.583 at 0 GPa to 0.652 at 20 GPa. If the isotropic Eliashberg electron-phonon coupling theory is used to simulate the effect on the critical temperature $T_c$, such an increase in $λ$ results in a substantial increase of $T_c$ from 2.5~K at 0 GPa to 4~K at 20 GPa. This shows that examining the effect of pressure offers a chance to resolve the pairing mechanism in ThCoC$_2$.

cond-mat.supr-con↗

arXiv2021

The effect of Ni doping on the electronic structure and superconductivity in the noncentrosymmetric ThCoC2

ThCoC$_2$ is a non-BCS, noncentrosymmetric superconductor with $T_c \simeq 2.5$~K, in which pairing mechanism was suggested to be either spin fluctuations or the electron-phonon coupling. Earlier experimental work revealed that $T_c$ can be greatly enhanced upon Ni doping in ThCo$_{1-x}$Ni$_x$C$_2$, up to 12~K for $x = 0.4$. In this work, using the Korringa-Kohn-Rostoker method with the coherent potential approximation (KKR-CPA), the evolution of the electronic structure upon Ni doping was studied and the increase of the density of states at the Fermi level was found. The electron-phonon coupling constant $λ$ was calculated using the rigid muffin tin approximation (RMTA) and the increase in $λ(x)$ was found. This indirectly confirms the electron-phonon coupling scenario as the trend in $λ(x)$ is in qualitative agreement with the experiment when the electron-phonon pairing is assumed.

cond-mat.supr-con↗

arXiv2021

Electronic structure, electron-phonon coupling and superconductivity in noncentrosymmetric ThCoC2 from ab initio calculations

Superconductors without inversion symmetry in their crystal structure are known to exhibit unconventional properties. Recently, based on the measured temperature dependence of the magnetic field penetration depth, superconductivity in noncentrosymmetric $\mathrm{ThCoC_2}$ was proposed to be a nodal $d$-wave and mediated by the spin fluctuations. Moreover, a non-BCS behavior of the temperature dependence of the electronic specific heat and the magnetic upper critical field were reported. In this work, the electronic structure, phonons and electron-phonon coupling are studied in $\mathrm{ThCoC_2}$ on the basis of \textit{ab initio} computations. The effect of the spin-orbit coupling on the electronic structure and electron-phonon interaction is analyzed, and a large splitting of the electronic band structure is found. The calculated electron-phonon coupling constant $λ= 0.59$ remains in decent agreement with the experimental estimates, suggesting that the electron-phonon interaction is strong enough to explain superconductivity with $T_c \simeq 2.5$~K. Nevertheless, we show that the conventional isotropic Eliashberg formalism is unable to describe the thermodynamic properties of the superconducting state, as calculated temperature dependence of the electronic specific heat and magnetic penetration depth deviate from experiments, which is likely driven by the strong spin-orbit coupling and inversion symmetry breaking. In addition, to shed more light on the pairing mechanism, we propose to measure the carbon isotope effect, as our calculations based on the electron-phonon coupling predict the observation of the isotope effect with an exponent $α\simeq 0.15$.

cond-mat.supr-con↗

arXiv2021

MgPd$_2$Sb -- the first Mg-based Heusler-type superconductor

We report the synthesis and physical properties of a full Heusler compound, MgPd$_2$Sb, which we found to show superconductivity below $T_c$ = 2.2 K. MgPd$_2$Sb was obtained by a two-step solid-state reaction method and its purity and cubic crystal structure (Fm-3m, a=6.4523(1) Å) were confirmed by powder x-ray diffraction. Normal and superconducting states were studied by electrical resistivity, magnetic susceptibility, and heat capacity measurements. The results show that MgPd$_2$Sb is a type-II, weak coupling superconductor ($λ_{e-p}$ = 0.53). The observed pressure dependence of $T_c$ ($ΔT_c / p \approx $ -0.23 K/GPa) is one of the strongest reported for a superconducting Heusler compound. The electronic structure, phonons, and electron-phonon coupling in MgPd$_2$Sb were theoretically investigated. The obtained results are in agreement with the experiment, confirming the electron-phonon coupling mechanism of superconductivity. We compare the superconducting parameters tothose of all reported Heusler-type superconductors.

cond-mat.supr-con↗