Superconducting phases of YH9 under pressure

Mingyang Du; Zonglun Li; Defang Duan; Tian Cui

doi:10.1103/PhysRevB.108.174507

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Superconducting phases of YH9 under pressure

Mingyang Du, Zonglun Li, Defang Duan, Tian Cui

DOI 10.1103/PhysRevB.108.174507 · Physical Review B

T1

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Abstract

Yttrium superhydrides have attracted much attention due to their multiple stoichiometries and excellent superconductivity under high pressure. Especially, YH9 have a superconducting critical temperature (Tc) of 243 K, which is only second to LaH10 among all superconductors. It exhibits a positive pressure dependence of Tc below 200 GPa, contrary to the results of theoretical prediction. In order to explore the origin of Tc at low pressure, we extensively investigated the crystal structures of YH9 at different pressure, and found a distorted cage structure with a symmetry of Pnma. This phase has the lowest enthalpy at pressure below 220 GPa, and its x-ray-diffraction patterns is consistent with experimental data. Most importantly, its pressure dependence of Tc is in line with the experimental results indicating that the low Tc at low pressure mainly comes from the low-symmetry Pnma phase. Further calculations show the structural distortion in the Pnma phase strongly affects the lattice vibration and electron-phonon coupling induced a positive pressure dependence of Tc. This work uncovers a remarkable correlation between superconductivity and structural distortion, and provides insight into clarifying the dome-shaped superconducting phase diagram (Tc-P) in yttrium hydrides.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
YH9 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	243	201 GPa	unknown
YH9 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	262	182 GPa	unknown
YH9 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	230	300 GPa	unknown
YH4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	88	155 GPa	unknown
YH6 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	224	166 GPa	unknown
YH3 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	40	17.7 GPa	unknown
YH7 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	43	165 GPa	unknown
YH10 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	326	250 GPa	unknown
LaH10 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	250	170 GPa	unknown
LaH10 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	260	180 GPa	unknown
YH9 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	205	160 GPa	unknown
YH9 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	250	210 GPa	unknown
YH9 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	266	250 GPa	unknown