固体氢在极端压强下的超导性能

Superconductivity of Solid Hydrogen under Extreme Pressure

氢元素在常压下具有最简单的晶体结构和物理性质。随着压强增加,氢单质发生相变,由绝缘体转变为金属,被称为金属氢。数值模拟表明,金属氢具有高温超导电性,因此,金属氢研究也被称为高压物理领域的“圣杯”课题。利用基于密度泛函理论的第一性原理计算方法,对固体氢在极端高压(0.5~5.0 TPa)下的结构和超导电性开展了系统研究。研究结果表明:固体氢的高压相变序列为I4_(1)/amd→oC12→cI16;对于同一种结构,随着压强增加,电声耦合系数减小,费米面处电子态密度减小,特征振动频率增加,超导转变温度发生小幅变化;在2.0 TPa压强下,固体氢的超导转变温度高达418 K(库伦赝势经验值μ^(*)=0.10)。研究工作将为金属氢及其超导电性的后续理论和实验研究提供参考。

Hydrogen has the simplest crystal structure and physical properties at ambient pressure.As the pressure increases,hydrogen undergoes phase transition from insulator to metal,which being called metallic hydrogen.The numerical calculations also indicate that metallic hydrogen has high-temperature superconductivity,thus the metal hydrogen is also known as the holy grail of physics subject.In this paper,the structural phase transition and superconducting transition temperature(Tc) of solid hydrogen under extreme high pressure 0.5–5.0 TPa were studied by first principles based on density functional theory,which may provide knowledge reserved for subsequent theoretical and experimental studies of metallic hydrogen and its superconductivity.The results show that the phase transition sequence of solid hydrogen under extreme high pressure is:I4_1/amd→oC12→cI16.For the same structure,with the increase of pressure,the electronphonon-induced interaction decreases,the density of electronic states at the Fermi surface decreases,the vibration frequency increases,and the superconducting transition temperature changes.When the pressure is 2.0 TPa,the oC12 structure of solid hydrogen can obtain the highest Tc of 418 K(coulomb pseudopotential parameter μ~*=0.10).This work provides a reference for further theoretical and experimental research on metallic hydrogen and its superconductivity.