Electron-phonon coupling constant and BCS ratios in (La,Nd)-H superhydride

Abstract

Stoichiometric near room-temperature superconductors (i.e., $H_{3}S$ and $La{H}_{10}$) exhibit so high ground state upper critical field, $B_{c2}(0)>100T$, that the magnetic phase diagram in these materials cannot be measured in non-destructive experiments. However, recently, Semenok et al (arXiv2203.06500) proposed the idea to explore full magnetic phase diagram in NRTS samples in which the superconducting order parameter is suppressed by the magnetic element doping. If the element is uniformly distributed in the material, then the theory of the electron-phonon mediated superconductivity predicts the suppression of the order parameter in three-dimensional s-wave superconductor. Semenok et al (arXiv2203.06500) experimentally proved this idea by substituting La with the magnetic rare earth Nd in the $L{a}_{1-x}N{d}_x{H}_{10-y}$. As a result, $T_c$ in the $L{a}_{1-x}N{d}_x{H}_{10-y}$ (x=0.09) decreases to Tc~120 K, and the upper critical field decreases to $B_{c2}(T=41K)=55T$. While the exact hydrogen content should be further established in the $L{a}_{1-x}N{d}_x{H}_{10-y}$ (because similar $T_c$ suppression was observed in hydrogen deficient $La{H}_{10-y}$ reported by Drozdov et al (2019 Nature 569 528)), a significant part of the full magnetic phase diagram for $L{a}_{1-x}N{d}_x{H}_{10-y}$ (x=0.09) was measured. Here we analyzed reported Semenok et al (arXiv2203.06500) data for $L{a}_{1-x}N{d}_x{H}_{10-y}$ (x=0.09) compressed at P=180 GPa and deduced: (a) Debye temperature, $T_{\theta }=1156K$; (b) the electron-phonon coupling constant, ${\lambda }_{e-ph}=1.65$; (c) the ground state superconducting energy gap, $\Delta (0)=20.2meV$; (d) the gap-to-transition temperature ratio, $2\Delta (0)/k_B{T}_c=4.0$; and (e) the relative jump in specific heat at $T_c$, $\Delta C/C=1.68$. The deduced values indicate that $L{a}_{1-x}N{d}_x{H}_{10-y}$ (x=0.09; P=180 GPa) is moderately strong coupled s-wave superconductor.

arXiv comment13 pages, 3 figures

References in corpus (24)

• Conventional superconductivity at 203 K at high pressures
• Superconductivity at 250 K in lanthanum hydride under high pressures
• Evidence for superconductivity above 260 K in lanthanum superhydride at megabar pressures
• Anomalous high-temperature superconductivity in YH${}_6$
• Superconductivity at 161 K in Thorium Hydride $Th{H}_{10}$: Synthesis and Properties
• Superconductivity at 253 K in lanthanum-yttrium ternary hydrides
• Towards high-throughput superconductor discovery via machine learning
• Bose-Einstein to BCS Crossover Picture for High-T_c Cuprates
• Superconducting Phase-Diagram of H3S under High Magnetic Fields
• High-temperature superconductivity on the verge of a structural instability in lanthanum superhydride
• Superconductivity up to 243 K in yttrium hydrides under high pressure
• Effect of paramagnetic impurities on superconductivity in polyhydrides: $\text{s}$-wave order parameter in Nd-doped LaH${}_{10}$
• Classifying superconductivity in compressed H3S
• Critical temperature of an anisotropic superconductor containing both nonmagnetic and magnetic impurities
• Classifying superconductivity in Moiré graphene superlattices
• Mott-driven BEC-BCS crossover in a doped spin liquid candidate, kappa-(BEDT-TTF)4Hg2.89Br8
• Dynamic Superconductivity Responses in Photo-excited Optical Conductivity and Nernst Effect
• Effect of nonmagnetic and magnetic impurities on the specific heat jump in anisotropic superconductors
• Resonant multigap superconductivity at room temperature near a Lifshitz topological transition in sulfur hydrides
• Comparison of highly-compressed C2/m-SnH12 superhydride with conventional superconductors
• High-temperature superconductors as ionic metals
• Dimensional interpolation for metallic hydrogen
• Superconducting $I$$\overline{4}$3$m$ CSH${}_7$ model applied to resistive transition temperature data for compressed C-S-H at high pressure
• Metallization of hydrogen

Cited by in corpus (6)

• Progress, problems and prospects of room-temperature superconductivity
• Quantifying nonadiabaticity in major families of superconductors
• A-15 type superconducting hydride $L{a}_4{H}_{23}$: Nanograined structure with low strain, strong electron-phonon interaction, and moderate level of nonadiabaticity
• Quantifying the nonadiabaticity strength constant in recently discovered highly-compressed superconductors
• $d$-wave superconductivity as a model for diborides apart MgB${}_2$
• Fermi-liquid nonadiabatic highly-compressed cesium iodide superconductor