arXiv subjects

P. Král

Publications and source records attributed to P. Král.

5 recordsLinked to original sources

arXiv2026

Uniaxial stress enhanced anisotropic magnetoresistance and superconductivity in the kagome superconductor LaRu$_{3}$Si$_{2}$

Elucidating the role of the kagome electronic structure in determining the various quantum ground states is of fundamental importance. In this work, we employ in-plane uniaxial stress as a tuning parameter to probe the electronic structure and its impact on the superconducting and normal-state properties of the kagome superconductor LaRu$_{3}$Si$_{2}$, combining magnetotransport measurements with first-principles calculations. We identify a pronounced anisotropy in both the upper critical field and the normal-state magnetoresistance, indicating strong electronic anisotropy despite the three-dimensional crystal structure. Furthermore, we find that the superconducting transition temperature $T_{\rm c}$ increases under in-plane stress applied within the kagome plane, although the enhancement is modest, reaching approximately 0.3 K at 0.6 GPa. Furthermore, the absolute magnetoresistance exhibits a pronounced increase from about 22${\%}$ at zero stress to 35${\%}$ at 0.6 GPa, indicating a substantial modification of the normal state above $T_{\rm c}$. Previous studies have reported time-reversal-symmetry (TRS) breaking below a temperature scale that coincides with the onset of magnetoresistance. The simultaneous enhancement of both $T_{\rm c}$ and magnetoresistance under stress therefore suggests a positive correlation between superconductivity and normal-state electronic and magnetic properties in LaRu$_{3}$Si$_{2}$. Detailed calculations demonstrate that stress-induced changes in $T_{\rm c}$ arise from the joint evolution of the total density of states and the flat band, whereas the large magnetoresistance enhancement is dominated by the stress-driven downward shift of the Ru $dz^{2}$ kagome flat band.

cond-mat.supr-con↗

arXiv2026

Divergent Pressure Response of Superconductivity in Sc$_{6}$MTe$_{2}$ ($M$ = Fe, Ru and Ir)

Identifying and understanding non-BCS superconductivity remains a central challenge in condensed-matter physics. Here we focus on the Sc$_{6}$MTe$_{2}$ family (M =d-electron metal), which provides a unique platform of isostructural compounds exhibiting superconductivity across 3d, 4d, and 5d systems. Using hydrostatic pressure as an additional tuning parameter, muon-spin rotation ($μ$SR) and AC susceptibility measurements uncover strongly contrasting pressure responses of superconductivity across the Sc$_{6}$MTe$_{2}$ series. The superconducting transition temperature, $T_{\rm C}$ decreases under pressure in the 3d Fe-based compound but increases for the 4d Ru- and 5d Ir-based systems, with the Ru compound showing the largest enhancement of nearly 50% within 2 GPa. The superfluid density exhibits similarly distinct pressure dependences, remaining nearly pressure independent for Fe while decreasing with increasing pressure for Ru and Ir. This suggests fundamentally different correlations between $T_{\rm C}$ and the superfluid density. Together, these results indicate that superconductivity emerging from strongly correlated and spin-orbit-dominated regimes in Sc$_{6}$MTe$_{2}$ is likely governed by different microscopic mechanisms and offer a useful experimental basis for future microscopic theoretical studies.

cond-mat.supr-con↗

arXiv2025

Contrasting $c$-axis and in-plane uniaxial stress effects on superconductivity and stripe order in La$_{1.885}$Ba$_{0.115}$CuO$_4$

The cuprate superconductor La$_{2-x}$Ba$_x$CuO$_4$ (LBCO) near $x=0.125$ is a striking example of intertwined electronic orders, where 3D superconductivity is anomalously suppressed, allowing spin and charge stripe order to develop, in a manner consistent with the emergence of a pair-density-wave (PDW) state. Understanding this interplay remains a key challenge in cuprates, highlighting the necessity of external tuning for deeper insight. While in-plane (within the CuO plane) uniaxial stress enhances superconductivity and suppresses stripe order, the effects of $c$-axis compression (perpendicular to the CuO plane) remains largely unexplored. Here, we use muon spin rotation ($μ$SR) and AC susceptibility with an in situ piezoelectric stress device to investigate the spin-stripe order and superconductivity in LBCO-0.115 under $c$-axis compression. The measurements reveal a gradual suppression of the superconducting transition temperature ($T_{\rm c}$) with increasing $c$-axis stress, in stark contrast to the strong enhancement observed under in-plane stress. We further show that while in-plane stress rapidly reduces both the magnetic volume fraction ($V_{\rm m}$) and the spin-stripe ordering temperature ($T_{\rm so}$), $c$-axis compression has no effect, with $V_{\rm m}$ and $T_{\rm so}$ exhibiting an almost unchanged behavior up to the highest applied stress of 0.21 GPa. These findings demonstrate a strong anisotropy in stress response, underscoring the critical role of crystallographic anisotropy in governing competing electronic phases in LBCO.

cond-mat.supr-con↗

arXiv2024

Pressure-Induced Enhancement of Superfluid Density in Transition Metal Dichalcogenides with and without Charge Density Wave

Gaining a deeper understanding of the interplay between charge density wave (CDW) order and superconductivity in transition metal dichalcogenides (TMDs), particularly within the (4H/2H)-NbX$_{2}$ (X=Se,S) family, remains an open and intriguing challenge. A systematic microscopic study across various compounds in this family is therefore required to unravel this complex interplay. Here, we report on muon spin rotation and magnetotransport experiments investigating the effects of hydrostatic pressure on the superconducting transition temperature ($T_{\rm c}$), the temperature-dependent magnetic penetration depth ($λ_\mathrm{eff}$), and the charge density wave order (CDW) in two layered chalcogenide superconductors: 4H-NbSe$_{2}$, which exhibits CDW order, and 2H-NbS$_{2}$, which lacks such order. Our observations reveal a substantial 75$\%$ enhancement of the superfluid density ($n_{s}/m^{*}$) in 4H-NbSe$_{2}$ upon maximum applied pressure of 2 GPa, surpassing that of 2H-NbSe$_{2}$. Despite the absence of CDW order, a sizeable 20$\%$ growth in superfluid density is also observed for 2H-NbS$_{2}$ under an applied pressure of 1.8 GPa. Notably, the evaluated superconducting gaps in all these TMDs remain largely unaffected by changes in applied pressure, irrespective of pressure-induced partial suppression of CDW order in (4H/2H)-NbSe$_{2}$ or its general absence in 2H-NbS$_{2}$. These results underscore the complex nature of pressure-induced behaviors in these TMDs, challenging a simplistic view of competition solely between CDW order and superconductivity. Remarkably, the relationship between $n_{s}/m^{*}$ and $T_{\rm c}$ exhibits an unconventional correlation, indicating a noteworthy similarity with the behavior observed in cuprate, kagome, and iron-based superconductors.

cond-mat.supr-con↗

arXiv2023

Ambient and high-pressure electrical transport and structural investigations of magnetic Weyl semimetal PrAlGe

We present ambient and high-pressure electrical transport and structural properties of recently discovered magnetic Weyl semimetal PrAlGe. Electrical resistivity at ambient pressure shows an anomaly at $T_C$ = 15.1 K related to the ferromagnetic transition. Anomalous Hall effect (AHE) is observed below $T_C$. We observe a 1.4 K/GPa increase of $T_C$ with pressure, resulting in $T_C$ $\approx$ 47 K at 23.0 GPa. Strong competition between Lorentz force and spin-scattering mechanisms suppressed by magnetic field is deduced from the magnetoresistance measurements under pressure. As in the ambient pressure case, the AHE is found to be present below $T_C$ up to the highest applied pressure. We observe a clear anomaly in the pressure dependence of $T_C$, magnetoresistance and Hall effect at 12.5 GPa suggesting the occurrence of a pressure-induced electronic transition at this pressure. X-ray diffraction (XRD) experiment under pressure revealed the lattice structure to be stable up to $\sim$19.6 GPa with the absence of any symmetry changing structural phase transition from the initial $I4_1md$ structure. Careful analysis of the pressure dependent XRD data reveal an isostructural transition near 11 GPa. Observed isostructural transition may be related to the pressure-induced electronic transition deduced from the magnetoresistance and Hall effect data.

cond-mat.mtrl-sci↗