Anomalous High‐Temperature Superconductivity in YH<sub>6</sub>

Troyan, I. A.; Semenok, Dmitrii V.; Kvashnin, Alexander G.; Sadakov, A. V.; Sobolevskiy, O. A.; Pudalov, V. M.; Иванова, А. Г.; Prakapenka, Vitali B.; Greenberg, Eran; Gavriliuk, Alexander; Lyubutin, I. S.; Struzhkin, Viktor V.; Bergara, Aitor; Errea, Ion; Bianco, Raffaello; Calandra, Matteo; Mauri, Francesco; Monacelli, Lorenzo; Akashi, Ryosuke; Oganov, Artem R.

doi:10.1002/adma.202006832

Cited by 256 publications

(273 citation statements)

References 78 publications

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“…2a ) and the c / a ratios of bct- YH 4 and hcp -YH 9 (Fig. 2b ) agree well with the theoretical predictions 22 – 24 , 26 , 31 , 32 , which justifies the assignment of compositions for the hydrides with H/Y > 3.…”

Section: Resultssupporting

confidence: 85%

“…Here, we also discuss the contradictions between different experimental data for the yttrium-hydrogen system. Our preliminary report 25 and the present more comprehensive data are in good agreement with the data from Troyan et al 26 but evidently contradict the claim of T c = 262 K at 182 GPa reported by Snider et al 27 .…”

Section: Introductionsupporting

confidence: 81%

“…Open black circles, stars, squares and triangles correspond to the theoretically predicted structures for YH 9 22 , YH 6 22 – 24 , 26 , YH 4 22 – 24 , 26 and YH 3 31 , 32 , respectively. Experimental data for pure Y 33 , 63 , YH 3 59 , YH 4 26 and YH 6 26 taken from the literature are depicted by the red symbols. Solid curves correspond to the Vinet 30 equation of state fitting.…”

Section: Resultsmentioning

confidence: 99%

“…Cyan, magenta and grey curves are the guides for the eye. Brown squares depict the data from Troyan et al 26 . Error bars are defined the same as in Drozdov et al 12 .…”

Section: Resultsmentioning

confidence: 99%

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

et al. 2021

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The discovery of superconducting H3S with a critical temperature Tc∼200 K opened a door to room temperature superconductivity and stimulated further extensive studies of hydrogen-rich compounds stabilized by high pressure. Here, we report a comprehensive study of the yttrium-hydrogen system with the highest predicted Tcs among binary compounds and discuss the contradictions between different theoretical calculations and experimental data. We synthesized yttrium hydrides with the compositions of YH3, YH4, YH6 and YH9 in a diamond anvil cell and studied their crystal structures, electrical and magnetic transport properties, and isotopic effects. We found superconductivity in the Im-3m YH6 and P63/mmc YH9 phases with maximal Tcs of ∼220 K at 183 GPa and ∼243 K at 201 GPa, respectively. Fm-3m YH10 with the highest predicted Tc > 300 K was not observed in our experiments, and instead, YH9 was found to be the hydrogen-richest yttrium hydride in the studied pressure and temperature range up to record 410 GPa and 2250 K.

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Section: Resultssupporting

confidence: 85%

Section: Introductionsupporting

confidence: 81%

Section: Resultsmentioning

confidence: 99%

“…Cyan, magenta and grey curves are the guides for the eye. Brown squares depict the data from Troyan et al 26 . Error bars are defined the same as in Drozdov et al 12 .…”

Section: Resultsmentioning

confidence: 99%

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

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“…Other current participants in the race are hydrogen-rich materials, such as H 3 S, LaH 10 , Li 2 MgH 16 , YH 6 , etc. [81][82][83][84][85]. In these systems, the large transition temperature results from the large vibrations of light hydrogens, which increase the electron-phonon coupling.…”

Section: Discussionmentioning

confidence: 99%

Topological polarization, dual invariants, and surface flat bands in crystalline insulators

2021

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We describe a crystalline topological insulator (TI) phase of matter that exhibits spontaneous polarization in arbitrary dimensions. The bulk polarization response is constructed by coupling the system to geometric deformations of the underlying crystalline order, represented by local lattice vectors-the elasticity tetrads. This polarization results from the presence of (approximately) flat bands on the surface of such TIs. These flat bands are a consequence of the bulk-boundary correspondence of polarized topological media, and contrary to related nodal line semimetal phases also containing surface flat bands, they span the entire surface Brillouin zone. We also present an example Hamiltonian exhibiting a Lifshitz transition from the nodal line phase to the TI phase with polarization. In addition, we discuss a general classification of three-dimensional (3D) crystalline TI phases and invariants in terms of the elasticity tetrads. The phase with polarization naturally arises from this classification as a dual to the previously better-known 3D TI phase exhibiting quantum (spin) Hall effect. Besides polarization, another implication of the large surface flat band is the susceptibility to interaction effects such as superconductivity: The mean-field critical temperature is proportional to the size of the flat bands, and this type of system may hence exhibit superconductivity with a very high critical temperature.

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Sr‐Doped Superionic Hydrogen Glass: Synthesis and Properties of SrH₂₂

et al. 2022

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experimental metallization limit moving step by step from 150 [4] to 430-500 GPa. [1,5] A consistent increase in pressure leads to a series of phase transitions in solid hydrogen (phases Ι-V [1,5] ), gradual quenching of the Raman signals, and darkening of the sample down to a complete loss of transparency. Despite a significant progress in achieving ultrahigh pressures in the last five years, detecting superconductivity of metallic hydrogen remains an unsolved problem. Studies of the electrical conductivity at pressures above 400 GPa remain very challenging.In 2004, N. Ashcroft suggested that the precompression effects caused by chemical bonding to other atoms may help to convert hydrogen to a metallic state. Fifteen years later, this idea was confirmed in the synthesis of many metallic and superconducting hydrides such as H 3 S, [6,7] LaH 10 , [8,9] YH 6 , [10,11] YH 9 , [11,12] ThH 10 , [13] CeH 9 , [14] PrH 9 , [15] NdH 9 , [16] and so forth. It is believed now that the superconducting properties of these compounds are due to the presence of a sublattice of metallic hydrogen, which is formed in pure hydrogen only at pressures of 500-700 GPa.There must be an intermediate link between these two forms of hydrogen, metallic and superconducting, and a molecular Recently, several research groups announced reaching the point of metallization of hydrogen above 400 GPa. Despite notable progress, detecting superconductivity in compressed hydrogen remains an unsolved problem. Following the mainstream of extensive investigations of compressed metal polyhydrides, here small doping of molecular hydrogen by strontium is demonstrated to lead to a dramatic reduction in the metallization pressure to ≈200 GPa. Studying the high-pressure chemistry of the Sr-H system, the formation of several new phases is observed: C2/m-Sr 3 H 13 , pseudocubic SrH 6 , SrH 9 with cubic F m 43 -Sr sublattice, and pseudo tetragonal superionic P1-SrH 22 , the metal hydride with the highest hydrogen content (96 at%) discovered so far. High diffusion coefficients of hydrogen in the latter phase D H = 0.2-2.1 × 10 −9 m 2 s −1 indicate an amorphous state of the H-sublattice, whereas the strontium sublattice remains solid. Unlike Ca and Y, strontium forms molecular semiconducting polyhydrides, whereas calcium and yttrium polyhydrides are high-T C superconductors with an atomic H sublattice. The discovered SrH 22 , a kind of hydrogen sponge, opens a new class of materials with ultrahigh content of hydrogen.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202200924.

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Anomalous High‐Temperature Superconductivity in YH₆

Cited by 256 publications

References 78 publications

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

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

Topological polarization, dual invariants, and surface flat bands in crystalline insulators

Sr‐Doped Superionic Hydrogen Glass: Synthesis and Properties of SrH₂₂

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Anomalous High‐Temperature Superconductivity in YH6

Cited by 256 publications

References 78 publications

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

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

Topological polarization, dual invariants, and surface flat bands in crystalline insulators

Sr‐Doped Superionic Hydrogen Glass: Synthesis and Properties of SrH22

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Anomalous High‐Temperature Superconductivity in YH₆

Sr‐Doped Superionic Hydrogen Glass: Synthesis and Properties of SrH₂₂