arXiv subjects

I. Kovalchuk

Publications and source records attributed to I. Kovalchuk.

3 recordsLinked to original sources

arXiv2025

Point-contact enhanced superconductivity in trigonal PtBi2: quest for the origin of high-Tc

We studied enhanced superconductivity in point contacts (PCs) based on a type-I Weyl semimetal trigonal t-PtBi2 using both normal metal (Ag, Cu, Pt) and ferromagnetic (Fe, Co, Ni) tips by measuring the differential resistance dV/dI(V) curves. In most cases, the value of the superconducting critical temperature Tc ranges between 3 and 5 K, which is several times higher than the maximum bulk Tc. Notably, among the various PCs we examined, a few achieved Tc values as high as 8 K, including those with both normal and ferromagnetic tips. Additionally, the critical magnetic field is also highly enhanced in these PCs and reaches up to several Tesla. The common reason for the Tc increase may be related to pressure/strain caused during the PC's formation. It is worth noting that a greater increase in Tc is observed in PCs formed at the edge of the sample flake, compared to those formed on the plane of the platelet. The results also reveal that the enhancement of Tc in PCs based on t-PtBi2 is compatible with ferromagnetic tip, which may suggest a potentially complex nature of enhanced superconductivity. Our findings besides suggest that t-PtBi2 is a promising candidate for realizing topological superconductivity at more accessible temperatures.

cond-mat.supr-con↗

arXiv2025

Fermi surface evolution in Weyl semimetal t-PtBi$_2$ probed by transverse transport properties

The combination of non-trivial topology and superconductivity opens to novel quantum devices. The discovery of intrinsic materials where such properties appear together represents a frontier in modern condensed matter physics. Trigonal PtBi$_2$ has recently emerged as a possible candidate, being the first example of superconducting type-I Weyl semimetal. However, several aspects of this promising compound still need to be unveiled, concerning its complicated band structure, the actual role of Weyl points in determining its electronic properties and the nature of the superconducting transition. In this work, we experimentally investigated a t-PtBi$_2$ single crystal by means of the Hall and Nernst effects. In particular, we revealed a change of regime in its electronic properties, which is compatible with a temperature and magnetic field evolution of hole-like pockets in the Fermi Surface.

cond-mat.supr-con↗

arXiv2020

Polymorphic PtBi2: Growth, structure and superconducting properties

PtBi$_2$ is a polymorphic system with interesting electronic properties. Here we report optimized crystal growth and structural characterization of pyrite-type and trigonal modification of PtBi$_2$. Selected area electron diffraction, X-ray powder diffraction and further Rietveld refinement confirms that trigonal PtBi$_2$ crystallizes in non-centrosymmetric $P31m$ space group, pyrite-type PtBi$_2$ in $Pa\bar{3}$ space group. Series of Pt$_{1-x}$Rh$_x$Bi$_2$ samples was obtained for $x=0, 0.03, 0.35$ in the trigonal PtBi$_2$ structure. These Pt$_{1-x}$Rh$_x$Bi$_2$ compounds become superconducting where critical temperature increases from $T_c=600$ mK for $x=0$ up to $T_c=2.7$ K for $x=0.35$. Furthermore we calculate the electronic band structure, using the structure parameters obtained. The calculated density of states (DOS) shows a minimum for the stochiometric compound at the Fermi level. These findings warrant further research by broader array of experimental techniques, as well as the effect of the substitution on the non-trivial band structure.

cond-mat.mtrl-sci↗