Non‐Fermi‐Liquid Behavior of Superconducting SnH₄

Abstract

The chemical interaction of Sn with H2 by X‐ray diffraction methods at pressures of 180–210 GPa is studied. A previously unknown tetrahydride SnH4 with a cubic structure (fcc) exhibiting superconducting properties below TC = 72 K is obtained; the formation of a high molecular C2/m‐SnH14 superhydride and several lower hydrides, fcc SnH2, and C2‐Sn12H18, is also detected. The temperature dependence of critical current density JC(T) in SnH4 yields the superconducting gap 2Δ(0) = 21.6 meV at 180 GPa. SnH4 has unusual behavior in strong magnetic fields: B,T‐linear dependences of magnetoresistance and the upper critical magnetic field BC2(T) ∝ (TC – T). The latter contradicts the Wertheimer–Helfand–Hohenberg model developed for conventional superconductors. Along with this, the temperature dependence of electrical resistance of fcc SnH4 in non‐superconducting state exhibits a deviation from what is expected for phonon‐mediated scattering described by the Bloch‐Grüneisen model and is beyond the framework of the Fermi liquid theory. Such anomalies occur for many superhydrides, making them much closer to cuprates than previously believed.

Quantifying the Nonadiabaticity Strength Constant in Recently Discovered Highly Compressed Superconductors

“…Thus, the experiment [1,3,25] remains the final criterion. Therefore, the confirmation of the predicted T c in order to determine the other fundamental ground-state parameters, including the upper critical field, B c2 (0); the lower critical field, B c1 (0) [12,22]; the self-field critical current density, J c (s f , T) [24,[82][83][84]; the London penetration depth, λ(0) [22,23,85,86]; the superconducting energy gap amplitude, ∆(0) [87][88][89]; and gap symmetry [90,91]; is the task of the experiment and the data analysis.…”

“…This research field represents one of the most fascinating scientific and technological explorations in modern condensed-matter physics. In this area of research, advanced first-principles calculations [2][3][4][5][6][7][8][9][10][11] are essential parts of the experimental quest for the discovery of new hydrides phases [12][13][14][15][16][17][18][19][20][21], and both of these directions drive the development of new experimental techniques with which to study highly pressurized materials [22][23][24][25][26][27][28][29][30][31].…”

“…From 2015 until now, several dozen high-temperature superconducting polyhydride phases have been discovered and studied [1,[12][13][14][15][16][17][18][19][20][21]24,[32][33][34][35][36][37][38][39][40][41][42][43][44][45]. At the same time, highpressure studies of superconductivity and high-pressure material synthesis [46][47][48] in nonhydrides (including cuprates [49][50][51][52]) have also progressed [53][54][55][56][57][58][59][60][61][62], including the observation of T c > 26 K in highly compressed elemental titanium [63,64] and scandium [65,66], and the discovery that T onset c ∼ = 78 K [67,68] and T zero c ∼ = 45 K [69]…”