arXiv subjects

Rafał Kurleto

Publications and source records attributed to Rafał Kurleto.

5 recordsLinked to original sources

arXiv2026

Probing bulk superconductivity in centrosymmetric Te-doped PtBi$_2$ single crystals

The Weyl semimetal $γ$-PtBi$_2$ has been shown to be one of the most promising novel materials, recently proposed as a topological i-wave superconductor. A crucial requirement for observing this physics is the absence of inversion symmetry in its trigonal $P31m$ crystal structure. Centrosymmetry has been reported to be readily restored in the $P\overline{3}m1$ structure upon electron doping, partially substituting Bi with as little as 2% Te. In this work, we synthesized Te-doped PtBi$_{2-x}$Te$_{x}$ samples and thoroughly investigated the bulk superconductivity of selected single crystals with nominal composition PtBi$_{1.96}$Te$_{0.04}$, exhibiting the highest superconducting volume fraction of $\sim100$%. Single crystal XRD measurements confirm the centrosymmetric $P\overline{3}m1$ structure in our samples, whereas bulk superconductivity with a critical temperature of $T_\mathrm{c} \approx 2.4\,$K was observed in magnetization and specific heat measurements. The upper critical fields for two different orientations were determined as $H^{\parallel}_{\mathrm{c2}}(0)\approx 6.3\,$kOe for in-plane and $H^{\perp}_{\mathrm{c2}}(0)\approx 4.7\,$kOe for out-of-plane magnetic fields. Robust superconductivity was also found in resistance and point contact measurements, where the latter showed a slight enhancement of the critical temperature up to $T_\mathrm{c} \sim 3\,$K. Finally, ARPES measurements corroborate the centrosymmetric structure of our samples, showing a single surface termination and the absence of Fermi arcs.

cond-mat.supr-con↗

arXiv2026

Magnetically tunable symmetry-enforced nodal lines producing huge anomalous Hall conductivity in altermagnetic $α$-MnTe

Altermagnetic $α$-MnTe exhibits huge anomalous Hall conductivity (AHC) up to room-temperature together with weak ferromagnetism arising from spin and orbital polarizations. We clarify the origin of the large value of the AHC by identifying two sets of distinct symmetry-enforced nodal lines in the valence bands with Mn character, located at $k_z=0$ and $k_z=\fracπ{c}$, protected by mirror symmetry $M_z$ and glide symmetry $G_z = \{M_z\,|\,0,0,\tfrac{c}{2}\}$, respectively. Both nodal lines are energy-dependent with an approximate C$_6$ symmetry, which is reduced to an exact C$_2$ symmetry due to the presence of the Néel vector. The highest valence band exhibits a Mexican-hat dispersion, whereas the second-highest valence band exhibits an inverted Mexican-hat dispersion, with nodal lines at the crossing between the two bands. Within first-principles accuracy, we demonstrate that these nodal lines give rise to the large AHC observed experimentally and exhibit a strong interplay with the weak ferromagnetism. We further show that even a small spin canting strongly modifies the nodal lines and the AHC, making them both magnetically tunable. By disentangling the altermagnetic and ferromagnetic contributions to the AHC, the altermagnetic contribution dominates at small canting angles, while the ferromagnetic contribution becomes sizeable for larger values. Using linear dichroism in angle-resolved photoemission spectroscopy, we show a signature of the nodal line at the border of the Brillouin zone.

cond-mat.mtrl-sci↗

arXiv2025

Non-altermagnetic spin texture in MnTe

Recently, altermagnets have emerged as promising candidates in spintronics, uniquely combining large spin-polarized electronic states with zero net magnetization. A prominent example is $α$-MnTe, whose altermagnetic spin splitting, i.e., the degeneracy lift in momentum space induced by collinear magnetic order, has been experimentally observed. However, the direct evidence of its $g$-wave spin polarization, the key property for altermagnetic spintronics, is thus far lacking. By combining high-resolution spin- and angle-resolved photoemission spectroscopy (SARPES) with first-principles calculations, we reveal a $k_z$-independent, Rashba-like spin texture in $α$-MnTe. Our results indicate that the observed spin polarization is primarily governed by spin-orbit coupling, whereas the magnetic order contributes to the splitting of energy bands but plays a much less dominant role in spin polarization due to the multi-domain nature. From this result, we further establish a way to prescreen altermagnet candidates that favor the formation of large antiferromagnetic domains based on symmetry analysis. Our work elucidates the interplay between magnetic order and spin-orbit coupling in governing spin polarization in altermagnet candidates, and thereby advances the materials design paradigm for spin-functional devices.

cond-mat.mtrl-sci↗

arXiv2023

Potential Lifshitz transition at optimal substitution in nematic pnictide Ba$_{1-x}$Sr$_x$Ni$_2$As$_2$

BaNi$_2$As$_2$ is a structural analog of the pnictide superconductor BaFe$_2$As$_2$, which, like the iron-based superconductors, hosts a variety of ordered phases including charge density waves (CDWs), electronic nematicity, and superconductivity. Upon isovalent Sr substitution on the Ba site, the charge and nematic orders are suppressed, followed by a sixfold enhancement of the superconducting transition temperature ($T_c$). To understand the mechanisms responsible for enhancement of $T_c$, we present high-resolution angle-resolved photoemission spectroscopy (ARPES) measurements of the Ba$_{1-x}$Sr$_{x}$Ni$_2$As$_2$ series, which agree well with our density functional theory (DFT) calculations throughout the substitution range. Analysis of our ARPES-validated DFT results indicates a Lifshitz transition and reasonably nested electron and hole Fermi pockets near optimal substitution where $T_c$ is maximum. These nested pockets host Ni $d_{xz}$/$d_{yz}$ orbital compositions, which we associate with the enhancement of nematic fluctuations, revealing unexpected connections to the iron-pnictide superconductors. This gives credence to a scenario in which nematic fluctuations drive an enhanced $T_c$.

cond-mat.supr-con↗

arXiv2021

Growth, characterization and Chern insulator state in MnBi$_2$Te$_4$ via the chemical vapor transport method

As the first intrinsic antiferromagnetic topological insulator, MnBi$_2$Te$_4$ has provided a platform to investigate the interplay of band topology and magnetism as well as the emergent phenomena arising from such an interplay. Here we report the chemical-vapor-transport (CVT) growth and characterization of MnBi$_2$Te$_4$, as well as the observation of the field-induced quantized Hall conductance in 6-layer devices. Through comparative studies between our CVT-grown and flux-grown MnBi$_2$Te$_4$ via magnetic, transport, scanning tunneling microscopy, and angle-resolved photoemission spectroscopy measurements, we find that CVT-grown MnBi$_2$Te$_4$ is marked with higher Mn occupancy on the Mn site, slightly higher Mn$_{\rm{Bi}}$ antisites, smaller carrier concentration and a Fermi level closer to the Dirac point. Furthermore, a 6-layer device made from the CVT-grown sample shows by far the highest mobility of 2500 cm$^2$V$\cdot$s in MnBi$_2$Te$_4$ devices with the quantized Hall conductance appearing at 1.8 K and 8 T. Our study provides a new route to obtain high-quality single crystals of MnBi$_2$Te$_4$ that are promising to make superior devices and realize emergent phenomena, such as the layer Hall effect and quantized anomalous hall effect, etc.

cond-mat.mtrl-sci↗