Palladium hydrides display the largest isotope effect anomaly known in the literature. Replacement of hydrogen with the heavier isotopes leads to higher superconducting temperatures, a behavior inconsistent with harmonic theory. Solving the self-consistent harmonic approximation by a stochastic approach, we obtain the anharmonic free energy, the thermal expansion, and the superconducting properties fully ab initio. We find that the phonon spectra are strongly renormalized by anharmonicity far beyond the perturbative regime. Superconductivity is phonon mediated, but the harmonic approximation largely overestimates the superconducting critical temperatures. We explain the inverse isotope effect, obtaining a -0.38 value for the isotope coefficient in good agreement with experiments, hydrogen anharmonicity being mainly responsible for the isotope anomaly. © 2013 American Physical Society.

First-principles theory of anharmonicity and the inverse isotope effect in superconducting palladium-hydride compounds / Errea, I.; Calandra, M.; Mauri, F.. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 111:17(2013). [10.1103/PhysRevLett.111.177002]

First-principles theory of anharmonicity and the inverse isotope effect in superconducting palladium-hydride compounds

Calandra M.;
2013-01-01

Abstract

Palladium hydrides display the largest isotope effect anomaly known in the literature. Replacement of hydrogen with the heavier isotopes leads to higher superconducting temperatures, a behavior inconsistent with harmonic theory. Solving the self-consistent harmonic approximation by a stochastic approach, we obtain the anharmonic free energy, the thermal expansion, and the superconducting properties fully ab initio. We find that the phonon spectra are strongly renormalized by anharmonicity far beyond the perturbative regime. Superconductivity is phonon mediated, but the harmonic approximation largely overestimates the superconducting critical temperatures. We explain the inverse isotope effect, obtaining a -0.38 value for the isotope coefficient in good agreement with experiments, hydrogen anharmonicity being mainly responsible for the isotope anomaly. © 2013 American Physical Society.
2013
17
Errea, I.; Calandra, M.; Mauri, F.
First-principles theory of anharmonicity and the inverse isotope effect in superconducting palladium-hydride compounds / Errea, I.; Calandra, M.; Mauri, F.. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 111:17(2013). [10.1103/PhysRevLett.111.177002]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11572/260236
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