Dr. Matteo Calandra, IMPMC-UPMC

Jeudi 15 Octobre 2015 14h
Amphi Holweck, Esc C, 1ème etage

Titre:High-Pressure Hydrogen Sulfide from First Principles:A Strongly Anharmonic Phonon-Mediated Superconductor

The recent discovery of superconductivity in high pressure HS2 with the
highest known Tc=205 K, opens new perspectives in the field by upturning
the conventional wisdom that an high Tc cannot be obtained via a phonon mediated pairing.

Here, we use first-principles calculations to study structural, vibrational,and superconducting properties of H2S at high pressures.

The inclusion of zero-point energy leads to two different possible dissociations of H2S,namely 3H2S in H3S+S and 5H2S in H3S+HS2, where both H3S and HS2 are metallic.

We show that HS2 is indeed superconductor, but with much lower Tc and cannot explain the measured Tc=205K at 200 GPa.
For H3S, we perform nonperturbative calculations of anharmonic effects within the self-consistent harmonic approximation and show that the harmonic approximation strongly overestimates the electron-phonon interaction (lambda=2.64 at 200 GPa) and Tc.
Anharmonicity hardens H-S bond-stretching modes and softens H-S bond-bending modes.
As a result, the electron-phonon coupling is suppressed by 30% (lambda=1.84 at 200 GPa).
Moreover, while at the harmonic level Tc decreases with increasing pressure, the inclusion of anharmonicity leads to a Tc that is almost independent of pressure.

High-pressure hydrogen sulfide is a strongly anharmonic superconductor.

[1] I. Errea et al. , Phys. Rev. Lett. 114, 157004 (2015)
[2] Li, et al. , arXiv:1508.03900
More information at

Haut de page

À lire aussi...

Pr. Guy Deutscher, School of Physics and Astronomy Tel Aviv University

Jeudi 22 Octobre 2015 14h Amphi Holweck, Esc C, 1ème etage Magnetic properties of granular aluminum L’aluminium granulaire, composé de (...) 

> Lire la suite...

Matthieu Delbecq, Center for Emergent Matter Science RIKEN

Jeudi 26 Novembre 2015 14h Amphi Holweck, Esc C, 1ème etage Multiple spin qubits in semiconductor quantum dots subject to nuclear spin bath (...) 

> Lire la suite...