arXiv subjects

V. V. Chistyakov

Publications and source records attributed to V. V. Chistyakov.

5 recordsLinked to original sources

arXiv2024

Debye temperature, electron-phonon coupling constant, and three-dome shape of crystalline strain as a function of pressure in highly compressed La$_3$Ni$_2$O$_{7-δ}$

Besides ongoing studies of phase structural transitions, pairing mechanism, and physical properties of recently discovered highly compressed high-temperature superconductor La$_3$Ni$_2$O$_{7-δ}$, here we explored a possibility for the electron-phonon pairing mechanism as an origin of the superconducting state and determined the microcrystalline strain, $ε(P)$, in high pressure $Fmmm$-phase, and low-pressure $Ammm$-phase of this nickelate. To do this, we analyzed temperature dependent resistance and extracted pressure dependent Debye temperature, $Θ_D(P)$, in La$_3$Ni$_2$O$_{7-δ}$ with an approximate value of $Θ_D(P = 25 GPa) = 550$ $K$. From this we established that the La$_3$Ni$_2$O$_{7-δ}$ is strong-coupled superconductor with the electron-phonon coupling constant $λ_{e-ph}(P=22.4 GPa) = 1.75$. This value is close to $λ_{e-ph} = 1.70$ of ambient pressure superconductors $Nb_3R (R = Sn, Al)$. To address ongoing discussion that the lattice strain can be the origin for the emergence of high-temperature superconductivity in the La$_3$Ni$_2$O$_{7-δ}$, we determined the microcrystalline strain, $0.011 < ε(P)$, in the high-pressure $Fmmm$-phase, and $ε(P) < 0.011$ of low-pressure $Fmmm$-phase. Our analysis showed that $ε(P)$ has three-dome shape in the pressure range of $1.6 GPa < P < 41.2 GPa$. One of these two $ε(P)$ deeps at $P \approx 15 GPa$ coincides with the pressure at which the $Ammm$-phase into the $Fmmm$-phase phase transition occurs. Based on our analysis, we proposed probable condition to observe the zero-resistance state in La$_3$Ni$_2$O$_{7-δ}$.

cond-mat.supr-con↗

arXiv2024

A-15 type superconducting hydride $La_4H_{23}$: Nanograined structure with low strain, strong electron-phonon interaction, and moderate level of nonadiabaticity

For seven decades by A-15 superconductors we meant metallic $A_3B$ alloys (where A is a transition metal, and B is groups IIIB and IVB element) discovered by Hardy and Hulm (Phys. Rev. 89, 884 (1953)). Nb3Ge exhibited the highest superconducting transition temperature, $T_c = 23 K$, among these alloys. One of these alloys, $Nb_3Sn$, is primary material in modern applied superconductivity. Recently Guo et al (arXiv:2307.13067) extended the family of superconductors where the metallic ions arranged in the beta tungsten (A-15) sublattice by observation of $T_{c,zero} = 81 K$ in $La_4H_{23}$ phase compressed at $P = 118 GPa$. Despite the $La_4H_{23}$ has much lower $T_c$ in comparison with near-room-temperature superconducting $LaH_{10}$ phase ($T_{c,zero} = 250 K$ at $P = 200 GPa$) discovered by Drozdov et al (Nature 569, 531 (2019)), the $La_4H_{23}$ holds the record high $T_c$ within A-15 family. Cross et al (Phys. Rev. B 109, L020503 (2024)) confirmed the high-temperature superconductivity in the compressed $La_4H_{23}$. In this paper, we analyzed available experimental data measured in $La_4H_{23}$ and found that this superconductor exhibits nanograined structure, 5.5 nm < D < 35 nm, low crystalline strain < 0.003, high electron-phonon coupling constant, 1.5 < $λ_{e-ph}$ < 2.55, and moderate level of the nonadiabaticity $Θ_{D}/T_{F}$. We found that derived $Θ_{D}/T_{F}$ and $T_c/T_F$ values for the $La_4H_{23}$ phase are similar to the ones in cuprates, pnictides, and near-room-temperature superconductors $H_3S$ and $LaH_{10}$, which implies that the $La_4H_{23}$ phase falls to unconventional superconductors band in the Uemura plot.

cond-mat.supr-con↗

arXiv2023

Magnetotransport in Weyl semimetal WTe2 single crystal

A WTe2 single crystal was grown by the chemical vapor transport method, and its electrical resistivity and galvanomagnetic properties were investigated. Single-band and two-band models were used to estimate the concentration and mobility of charge carriers in WTe2 at temperatures from 4.2 to 150 K.

cond-mat.mtrl-sci↗

arXiv2023

Electronic Transport in a Topological Semimetal WTe2 Single Crystal

Electrical resistivity, magnetoresistivity, and the Hall effect have been studied in a topological semimetal WTe2 single crystal in the temperature range from 12 to 200 K under magnetic fields up to 9 T. It has been found that quadratic temperature dependences of the electrical resistivity in the absence of a magnetic field and the conductivity in a magnetic field are observed at low temperatures, which is apparently associated with contributions from various scattering mechanisms. Single-band and two-band models were used to analyze data on the Hall effect and magnetoresistivity. These results indicate electron-hole compensation with a slight predominance of electron charge carriers.

cond-mat.str-el↗

arXiv2017

NMR studies of the topological insulator Bi2Te3

Te NMR studies were carried out for the bismuth telluride topological insulator in a wide range from room temperature down to 12.5 K. The measurements were made on a Bruker Avance 400 pulse spectrometer. The NMR spectra were collected for the mortar and pestle powder sample and for single crystalline stacks with orientations c parallel and perpendicular to field. The activation energy responsible for thermal activation. The spectra for the stack with c parallel to field showed some particular behavior below 91 K.

cond-mat.mes-hall↗