Symmetry and Higher Superconductivity in the Lower Elements

Abstract

Abstract:At one atmosphere 29 elements are classified as superconductors; at high pressures there are to date an additional 23, many of these being drawn from the lighter elements. The number of superconductors for the elements in combination appears to be illimitable. Observed symmetries in these systems generally include orderings in both nuclear and electronic degrees of freedom. The fluctuations impelling order in the electron sub-system include those originating with the nuclear degrees of freedom but also with the electrons themselves, both itinerant and localized. For the elements in combination coherent multipole fluctuations in localized states may arise, and the relative contributions of such excitations to electron-pairing is then of some especial interest. When the elements are placed in combination the effects of external pressure may be replicated in part by an equivalent internal pressure, this resulting from a form of chemical pre-compression.

Breakdown of the Migdal approximation at Lifshitz transitions with giant zero-point motion in the H3S superconductor

“…High temperature superconductivity has been found in other hydrides 5 like pressurized PH 3 with T c at about 100 K 6 , and it has been predicted in other hydrides like yttrium hydride 7 . Superconductivity in pressurized hydrides was proposed by Ashchroft and his collaborators 8 9 . The Universal Structure Predictor: Evolutionary Xtallography, USPEX, code 10 available today has allowed to predict the structure and high temperature superconductivity in pressurized sulfur hydride 11 12 13 .…”

Superconductivity above the lowest Earth temperature in pressurized sulfur hydride

“…Many years before high-temperature superconductivity in pressurized hydrides and hydrogen was proposed by Aschroft [45][46][47][48][49][50], Ginzburg [51,52] and Maksimov [53,54]. The theoretical predictions of high T c in solid hydrogen and hydrides at high pressure were based on the search of a system i) with a high-energy phonon mediating the pairing, because of the small mass of the hydrogen ion, ii) with a negative dielectric constant [52][53][54] and iii) at the verge of the superfluid-superconductor transition [49], where the transition temperature principally increases through the reduction in the associated Coulomb pseudopotential.…”

Lifshitz transitions and zero point lattice fluctuations in sulfur hydride showing near room temperature superconductivity

“…The Eremets's group research was motivated by the search for room temperature superconductivity predicted to emerge in metallic hydrogen and hydrides [21][22][23][24][25][26][27][28][29].…”

“…Therefore it was known that materials research for room temperate superconductivity cannot be driven simply by looking to increase the phonon energy and coupling strength in the cooper pairing. The theoretical predictions of high T c in solid hydrogen and hydrates at high pressure were based not only on the high frequency phonons mediating the pairing in solid hydrogen or hydrates but also on joint control of the electron electron interaction via the changes of the dielectric constant controlling the repulsive electron-electron interaction and the Coulomb energy [21][22][23][24][25][26][27][28][29] which can become negative [22,24,28] for an electronic system in the low density limit.…”