HighPressure Hydrogen Sulfide from First Principles: A Strongly Anharmonic PhononMediated Superconductor
Abstract
We use firstprinciples calculations to study structural, vibrational, and superconducting properties of H_{2}S at pressures P ≥200 GPa . The inclusion of zeropoint energy leads to two different possible dissociations of H_{2}S , namely 3 H_{2}S →2 H_{3}S +S and 5 H_{2}S →3 H_{3}S +HS_{2} , where both H_{3}S and HS_{2} are metallic. For H_{3}S , we perform nonperturbative calculations of anharmonic effects within the selfconsistent harmonic approximation and show that the harmonic approximation strongly overestimates the electronphonon interaction (λ ≈2.64 at 200 GPa) and T_{c}. Anharmonicity hardens HS bondstretching modes and softens HS bondbending modes. As a result, the electronphonon coupling is suppressed by 30% (λ ≈1.84 at 200 GPa). Moreover, while at the harmonic level T_{c} decreases with increasing pressure, the inclusion of anharmonicity leads to a T_{c} that is almost independent of pressure. Highpressure hydrogen sulfide is a strongly anharmonic superconductor.
 Publication:

Physical Review Letters
 Pub Date:
 April 2015
 DOI:
 10.1103/PhysRevLett.114.157004
 arXiv:
 arXiv:1502.02832
 Bibcode:
 2015PhRvL.114o7004E
 Keywords:

 74.62.Fj;
 63.20.dk;
 71.15.Mb;
 74.25.Jb;
 Pressure effects;
 Firstprinciples theory;
 Density functional theory local density approximation gradient and other corrections;
 Electronic structure;
 Condensed Matter  Superconductivity;
 Condensed Matter  Materials Science
 EPrint:
 5 pages + supplemental material