D. A. Knyazev

Max Planck Institute of Microstructure Physics

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Vasily S. Minkov

Max Planck Institute for Chemistry

M. I. Eremets

Max Planck Institute for Chemistry

P. P. Kong

Max Planck Institute for Chemistry

Mikhail A. Kuzovnikov

University of Edinburgh

Shirin Mozaffari

University of Tennessee at Knoxville

S. P. Besedin

Burdenko Neurosurgery Institute

Fedor Balakirev

Los Alamos National Laboratory

Luis Balicas

National High Magnetic Field Laboratory

АП

А. П. Дроздов

Max Planck Institute for Chemistry

Eran Greenberg

University of Chicago

Cooperative Institutions

Max Planck Institute of Microstructure Physics

Max Planck Society

Max Planck Institute for Chemistry

National High Magnetic Field Laboratory

Martin Luther University Halle-Wittenberg

Florida State University

Chinese Academy of Sciences

Russian Academy of Sciences

Los Alamos National Laboratory

Institute of Physics

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Superconductivity up to 243 K in yttrium hydrides under high pressure

arXiv (Cornell University) (2019)

P. P. Kong Vasily S. Minkov Mikhail A. Kuzovnikov S. P. Besedin A. P. Drozdov

The discovery of high-temperature conventional superconductivity in H3S with a critical temperature of Tc=203 K was followed by the recent record of Tc ~250 K in the face-centered cubic (fcc) lanthanum hydride LaH10 compound. It was realized in a new class of hydrogen-dominated compounds having a clathrate-like crystal structure in which hydrogen atoms form a 3D framework and surround a host atom of rare earth elements. Yttrium hydrides are predicted to have even higher Tc exceeding room temperature. In this paper, we synthesized and refined the crystal structure of new hydrides: YH4, YH6, and YH9 at pressures up to 237 GPa finding that YH4 crystalizes in the I4/mmm lattice, YH6 in Im-3m lattice and YH9 in P63/mmc lattice in excellent agreement with the calculations. The observed very high-temperature superconductivity is comparable to that found in fcc-LaH10: the pressure dependence of Tc for YH9 also displays a "dome like shape" with the highest Tc of 243 K at 201 GPa. We also observed a Tc of 227 K at 237 GPa for the YH6 phase. However, the measured Tcs are notably lower by ~30 K than predicted. Evidence for superconductivity includes the observation of zero electrical resistance, a decrease of Tc under an external magnetic field and an isotope effect. The theoretically predicted fcc YH10 with the promising highest Tc>300 K was not stabilized in our experiments under pressures up to 237 GPa.

Lanthanum

Room-temperature superconductor

Lattice constant

Lattice (music)

10.48550/arxiv.1909.10482

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Citations (84)

Superconductivity at 250 K in lanthanum hydride under high pressures

Nature (2019)

А. П. Дроздов P. P. Kong Vasily S. Minkov S. P. Besedin Mikhail A. Kuzovnikov

Room-temperature superconductor

Critical field

Ambient pressure

Lanthanum

BCS theory

10.1038/s41586-019-1201-8

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Citations (602)

Incorporation of 14C and 15N amino acids and nucleic bases into humus and the turnover of atomic-molecular composition

Eurasian Soil Science (1993)

A. D. Fokin D. A. Knyazev Yakov Kuzyakov

Humus

Source

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Superconductivity at 215 K in lanthanum hydride at high pressures

arXiv (Cornell University) (2018)

A. P. Drozdov Vasily S. Minkov S. P. Besedin P. P. Kong Mikhail A. Kuzovnikov

We synthesized lanthanum hydride (LaHx) by laser heating of lanthanum in hydrogen atmosphere at pressure P = 170 GPa. The sample shows a superconducting step at 209 K and 170 GPa and temperature dependence of resistance. By releasing the pressure to 150 GPa, the superconducting transition temperature Tc increases to 215 K - the record Tc. This finding supports a way of achieving Tc higher than the one in H3S (203 K) in hydrides with sodalite-like structures, first proposed for CaH6 (Tc=245 K) and later for yttrium and lanthanum hydrides where higher, room temperature superconductivity is expected.

Lanthanum

Sodalite

Superconducting transition temperature

10.48550/arxiv.1808.07039

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Citations (37)

Superconductivity up to 243 K in the yttrium-hydrogen system under high pressure

Nature Communications (2021)

P. P. Kong Vasily S. Minkov Mikhail A. Kuzovnikov А. П. Дроздов S. P. Besedin

The discovery of superconducting H

10.1038/s41467-021-25372-2

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Citations (342)

Free-radical condensation as a natural mechanism of the formation of humic acids

Eurasian Soil Science (2009)

D. A. Knyazev A. D. Fokin А. В. Очкин

Humus

Primary (astronomy)

Decarboxylation

10.1134/s106422930909004x

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Citations (13)

Superconducting phase diagram of H3S under high magnetic fields

Nature Communications (2019)

Shirin Mozaffari Dan Sun Vasily S. Minkov А. П. Дроздов D. A. Knyazev

We report the temperature dependence of the upper critical fields $\mu_0H_{c2}(T)$ of the high temperature superconductor H$_3$S under applied pressures of 155 and 160 GPa through the electrical resistance transition observed under DC and pulsed magnetic fields up to 65 T, a record high combination of fields and pressures. We find that $H_{c2}(T)$ generally follows the Werthamer, Helfand and Hohenberg (WHH) formalism at low fields, albeit with noticeable deviations upon approaching our experimental limit of $\mu_0H = 65$ T. In fact, $H_{c2}(T)$ displays a remarkably linear dependence on temperature over an extended temperature range also found in multigap or in strongly-coupled superconductors. The best fit of $H_{c2}(T)$ to the WHH formula yields a negligible value for the Maki parameter $\alpha$ and for spin-orbit scattering constant $\lambda_{\text{SO}}$. However, its behavior is relatively well-described by a model based on strong coupling superconductivity with a coupling constant $\lambda \sim 2$. Therefore, we conclude that H$_3$S behaves as a strong-coupled orbital-limited superconductor over the entire range of temperatures and fields used for our measurements.

10.1038/s41467-019-10552-y

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Citations (52)

Nuclear quadrupole contribution to the equilibrium isotope effect

Polyhedron (1999)

D. A. Knyazev Г. К. Семин А. В. Бочкарев

Kinetic isotope effect

10.1016/s0277-5387(99)00156-4

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Citations (17)

Observation of Néel-type skyrmions in acentric self-intercalated Cr1+δTe2

Nature Communications (2022)

Rana Saha H. L. Meyerheim Börge Göbel Binoy Krishna Hazra Hakan Deniz

Transition-metal dichalcogenides intercalated with 3d-transition metals within the van der Waals (vdW) gaps have been the focus of intense investigations owing to their fascinating structural and magnetic properties. At certain concentrations the intercalated atoms form ordered superstructures that exhibit ferromagnetic or anti-ferromagnetic ordering. Here we show that the self-intercalated compound Cr1+δTe2 with δ ≈ 0.3 exhibits a new, so far unseen, three-dimensionally ordered (2×2×2) superstructure. Furthermore, high resolution X-ray diffraction reveals that there is an asymmetric occupation of the two inequivalent vdW gaps in the unit cell. The structure thus lacks inversion symmetry, which, thereby, allows for chiral non-collinear magnetic nanostructures. Indeed, Néel-type skyrmions are directly observed using Lorentz transmission electron microscopy. The skyrmions are stable within the accessible temperature range (100-200 K) as well as in zero magnetic field. The diameter of the Néel skyrmions increases with lamella thickness and varies with applied magnetic field, indicating the role of long-range dipole fields. Our studies show that self-intercalation in vdW materials is a novel route to the formation of synthetic non-collinear spin textures.

Skyrmion

Superstructure

Point reflection

10.1038/s41467-022-31319-y

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Citations (51)