arXiv subjects

M. Bykov

Publications and source records attributed to M. Bykov.

7 recordsLinked to original sources

arXiv2026

Superconductivity of Tellurium Polyhydride with Tc above 90K

We report experimental diacovery of superconductivity (SC) in tellurium (Te) polyhydride. The compound was synthesized at high pressure and high temperature conditions using a diamond anvil cell combined with a laser heating system. Subsequent in situ transport measurements at high pressures, performed as a function of temperature and applied magnetic field, revealed a superconducting transition with a critical temperature Tc about 91 K at 263 GPa. The superconducting phase is assigned to TeH4 with characterized face shared TeH12 cage forming quasi molecular H2 units based on synchrotron x-ray diffraction experiments. Analysis of the SC behavior at magnetic fields yielded a Ginzburg Landau (GL) coherence length of approximately 54 angstroms. Tellurium polyhydride thus becomes another chalcogen polyhydride superconductor in addition to the landmark discovery of the first polyhydride high Tc SC SH3.

cond-mat.supr-con↗

arXiv2025

Isostructural phase transition and equation of state of type-I and type-VIII metallic sodium borosilicide clathrates

Electronic properties of silicon-based clathrates can be tuned by boron incorporation into the silicon cage network. Sodium borosilicides clathrate outstands with uncommon stoichiometry and expected metallic properties, in contrast to other alkali metal semiconductive Zintl borosilicides. In this study, we report an experimental investigation of the high-pressure behavior of type-I and type-VIII sodium borosilicide clathrates. An isostructural phase transition, marked by an abrupt volume collapse at 13 GPa, is observed exclusively in type-I sodium borosilicide clathrates. This transition is attributed to the pressure-induced diffusion of silicon atoms from the Si(6c) site. This mechanism provides the first experimental validation of a transition predicted theoretically for this class of materials. Isostructural phase transitions were only observed in type-I borosilicide. In contrast, the type-VIII borosilicide phase exhibits conventional elastic compression. The metallic character was established using reflectance spectroscopy over a wide energy range, in good agreement with crystallographic data on the boron content.

cond-mat.mtrl-sci↗

arXiv2023

Superconductivity with Tc 116K discovered in antimony polyhydrides

Superconductivity (SC) was experimentally observed for the first time in antimony polyhydride. The diamond anvil cell combined with laser heating system was used to synthesize the antimony polyhydride sample at high pressure and high temperature conditions. In-situ high pressure transport measurements as function of temperature with applied magnet are performed to study the SC properties. It was found that the antimony polyhydride samples show superconducting transition with critical temperature Tc 116 K at 184 GPa. The investigation of SC at magnetic field revealed that the superconducting coherent length ~40 angstroms based on Ginzburg Landau (GL) equation. Antimony polyhydride superconductor has the second highest Tc in addition to sulfur hydride among the polyhydrides of elements from main group IIIA to VIIA in periodic table.

cond-mat.supr-con↗

arXiv2019

FeOOH instability at the lower mantle conditions

Goethite, {\alpha}-FeOOH, is a major component among oxidized iron species, called rust, which formed as a product of metabolism of anoxygenic prokaryotes (1, 2) inhabiting the Earth from about 3.8 billion years (Gy) ago until the Great Oxidation Event (GOE) of about 2.5 Gy ago. The rust was buried on the ocean floor (1, 2) and had to submerge into the Earth mantle with subducting slabs due to the plate tectonics started about 2.8 Gy ago (3). The fate and the geological role of the rust at the lower mantle high-pressure and high-temperature(HPHT) conditions is unknown. We studied the behavior of goethite up to 82(2) GPa and 2300(100) K using in situ synchrotron single-crystal X-ray diffraction. At these conditions, corresponding to the coldest slabs at the depth of about 1000 km, {\alpha}-FeOOH decomposes to various iron oxides (Fe2O3, Fe5O7, Fe7O10, Fe6.32O9) and an oxygen-rich fluid. Our results suggest that recycling of the rust in the Earth mantle could contribute to oxygen release to the atmosphere and explain the sporadic increase of the oxygen level before the GOE linked to the formation of Large Igneous Provinces(4).

physics.geo-ph↗

arXiv2019

Revealing the complex nature of bonding in binary high-pressure compound FeO$_2$

Extreme pressures and temperatures are known to drastically affect the chemistry of iron oxides resulting in numerous compounds forming homologous series $n$FeO$\cdot m$Fe$_2$O$_3$ and the appearance of FeO$_2$. Here, based on the results of \emph{in situ} single-crystal X-ray diffraction, M\"ossbauer spectroscopy, X-ray absorption spectroscopy, and DFT+dynamical mean-field theory calculations we demonstrate that iron in high pressure cubic FeO$_2$ and isostructural FeO$_2$H$_{0.5}$ is ferric (Fe$^{3+}$), and oxygen has a formal valence less than two. Reduction of oxygen valence from 2, common for oxides, down to 1.5 can be explained by a formation of a localized hole at oxygen sites.

physics.geo-ph↗

arXiv2016

Phase-channel dynamics reveal the role of impurities and screening in a quasi-one-dimensional charge-density wave system

We investigate the low-energy phase excitations of the quasi-one-dimensional charge density wave (CDW) in $\mathrm{K}_{0.3}\mathrm{Mo}\mathrm{O}_3$, by direct probing of infrared-active CDW-lattice modes (phase-phonons) with ultrafast terahertz spectroscopy. Both the nonequilibrium response and temperature dependence of the bands are reconciled by generalizing the time-dependent Ginzburg-Landau theory, beyond that previously applied to the amplitude-phonons, to include impurity effects, while the photoinduced blue-shifts are attributed to a reduction of the electron-phonon coupling induced by a long-lived free-carrier population.

cond-mat.mes-hall↗

arXiv2015

Thermal expansion and compressibility of monogermanides of 3d-metals

Synchrotron diffraction as a function of temperature and pressure, specific heat, magnetic susceptibility and small-angle neutron scattering experiments have revealed an anomalous response of MnGe. Similar but less pronounced behavior has also been observed in Mn$_{1-x}$Co$_x$Ge and Mn$_{1-x}$Fe$_x$Ge solid solutions. Spin density fluctuations and Mn spin state instability are discussed as possible candidates for the observed effects.

cond-mat.mtrl-sci↗