Abstract
The high value of the isotope shift in sulfur hydrides supports a phonon-mediated pairing scenario of superconductivity for these high-temperature superconductors which are consistent with the Bardeen–Cooper–Schrieffer (BCS) framework. Knowing that a large electronic density of states enhances the critical temperature (Tc), generalized Fermi surface topologies are used to increase it. A multicomponent model within the BCS framework is proposed in this work for sulfur hydride superconductors. This model is used to evaluate some properties of the H3S superconductor. Strong and intermediate coupling effects are taken into account with the effective McMillan approximation, and the isotope coefficient is evaluated as a function of the coupling parameter as well as other relevant parameters of the model.
Highlights
Research on the possibility of room temperature superconductivity has been invigorated by the discovery of superconducting sulfur hydrides at very high pressure, about 155 gigapascals (GPa) [1, 2]
E high value of the isotope exponent in this material shows evidence of a phonon-mediated pairing mechanism, consistent with the BCS framework. e fact that the critical temperature varies with the isotopic mass is the evidence of the interaction between the electrons and lattice vibrations [12,13,14]. ese results are proof that the electron-phonon interaction is an important pairing mechanism in the sulfur hydrides [15,16,17]. e observation that the superconductivity in these superconductors shows strong sensitivity to the crystal lattice suggests the possibility of unconventional electron-phonon coupling
Based on the electronic band structure obtained from this material and on the results mentioned in this paragraph, we propose to evaluate the properties of sulfur hydrides with the topology of generalized Fermi surfaces modeled with band overlapping
Summary
Research on the possibility of room temperature superconductivity has been invigorated by the discovery of superconducting sulfur hydrides at very high pressure, about 155 gigapascals (GPa) [1, 2]. Based on the electronic band structure obtained from this material and on the results mentioned in this paragraph, we propose to evaluate the properties of sulfur hydrides with the topology of generalized Fermi surfaces modeled with band overlapping. Is model, which can be taken as a minimal singularity in the density of states, together with the BCS framework, predicts higher Tc values given that the energy band overlapping increases the DOS near the Fermi level [40,41,42]. An important requirement introduced in our model is that the band overlapping parameter is not larger than the phonon energy, Eph. e model with generalized Fermi surface topologies is extended to intermediate and strong coupling with the use of the McMillan effective approach to the Eliashberg equations. We will evaluate some properties of the sulfur hydride superconductor, H3S, as the isotope mass exponent, α, in terms of the coupling constant and the parameters of the model. e multiband scenario of superconductivity had previously been used to describe the isotope coefficient in other superconductor materials such as cuprate superconductors [43], hydrides [36, 44], and organic materials [45]
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