Accelerated materials design approaches based on structural classification: application to low enthalpy high pressure phases of SH3 and SeH3

We propose a methodology that efficiently asseses major characteristics in the energy landscape for a given space of configurations (crystal structures) under pressure. In this work we study SH

Emergent Magnéli-type crystal phases and their mixture in pressurized sulfur hydride

The pressure-induced superconductivity in sulfur hydride has recently received tremendous amount of interest for its record-breaking transition temperature (T

Possible High-Temperature Superconductivity in Hygrogenated Fluorine

Recent computational studies confirmed by experiment have established the occurrence of superconducting temperatures, T

Superconductivity in Hydrides Doped with Main Group Elements Under Pressure

A priori crystal structure prediction techniques have been used to explore the phase diagrams of hydrides of main group elements under pressure. A number of novel phases with the chemical formulas MHn, n > 1 and M = Li, Na, K, Rb, Cs; MHn, n > 2 and M= Mg, Ca, Sr, Ba; H

Metal hydrogen sulfide superconducting temperature

AbstractÉliashberg theory is generalized to the electronphonon (EP) systems with the not constant density of electronic states. The phonon contribution to the anomalous electron Green’s function (GF) is considered. The generalized Éliashberg equations with the variable density of electronic states are resolved for the hydrogen sulphide SHThe results of the solution of the Eliashberg equations for the Im-3m (170 GPa), Im-3m (200 GPa) and R3m (120 GPa) phases are presented. A peak value T

Effect of Hydrostatic Pressure on BiS2-Based Layered Superconductors: A Review

We report impact of hydrostatic pressure on the newly discovered BiS2 based superconductors. In last couple of years the new BiS2 based superconductor attracted great attention of the condensed matter physics community. These new layered BiS2-based compounds are very sensitive to the concentration of carriers doping and pressure that cause profound changes in their physical properties with appearance of superconductivity in the vicinity of their insulating/semiconducting state. The BiS2-based new compounds are expected to provide us with the next stage of exploring new superconductors and to discuss their exotic superconductivity mechanisms. In current review, we present most of our findings related to impact of hydrostatic pressure on superconductivity of new BiS2 based superconductors at one place.

High temperature superconductivity in sulfur hydride under ultrahigh pressure: A complex superconducting phase beyond conventional BCS

The recent report of superconductivity under high pressure at the record transition temperature of Tc =203 K in pressurized H2S has been identified as conventional in view of the observation of an isotope effect upon deuteration. Here it is demonstrated that conventional theories of superconductivity in the sense of BCS or Eliashberg formalisms cannot account for the pressure dependence of the isotope coefficient. The only way out of the dilemma is a multi-band approach of superconductivity where already small interband coupling suffices to achieve the high values of Tc together with the anomalous pressure dependent isotope coefficient. In addition, it is shown that anharmonicity of the hydrogen bonds vanishes under pressure whereas anharmonic phonon modes related to sulfur are still active.

The response of an individual vortex to local mechanical contact

Recently we reported a new way to manipulate vortices in thin superconducting films by local mechanical contact without magnetic field, current or altering the pinning landscape [1]. We use scanning superconducting interference device (SQUID) microscopy to image the vortices, and a piezo element to push the tip of a silicon chip into contact with the sample. As a result of the stress applied at the contact point, vortices in the proximity of the contact point change their location. Here we study the characteristics of this vortex manipulation, by following the response of individual vortices to single contact events. Mechanical manipulation of vortices provides local view of the interaction between strain and nanomagnetic objects, as well as controllable, effective, localized, and reproducible manipulation technique.

Evolution of superconductivity and magnetism in BiS2-based layered compounds

BiS2-based compounds constitute a new family of layered superconductors. In this article, several experimental findings on the superconductivity and related properties of the BiS2 family are reviewed. In particular, the focus is on the conditions required for the emergence of superconductivity and higher superconducting transition temperature in the BiS2 family: it is shown that optimizing the electron doping and crystal structure are important. Further, a few notable characteristics such as the coexistence of superconductivity and magnetism as well as the relation between the superconductivity and chargedensity- wave instability are introduced in brief.

Effect of spacer layer on flux-pinning properties of iron-based superconductors

We investigated the magnetic flux-pinning in iron-based 1111-type (REFeAsO, RE= rare earth) and 11- type (FeSe1−xTex) superconductors by third harmonic acmagnetic susceptibility measurements, a technique sensitive to the dynamics of magnetization, probing non-linear processes in flux pinning transport. Despite the larger thermal fluctuations due to the high critical temperature and large anisotropy, flux dynamics of 1111-type pnictides points out a more efficient pinning mechanism than the one in the 11-type chalcogenides. We have associated the stronger pinning in the 1111-family to the presence of REO (RE=rare earth) spacer layers separating the active FeAslayers unlike the 11-chalcogenides in which no spacer layers are present. Therefore, the disorder in the FeAs layers induced by the misfit strain due to spacer layers has an important role in the enhanced flux pinning of 1111-type superconductors.