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Abstract Recently, tremendous research interest has been aroused in clathrate superhydrides. However, their microscopic properties, especially the superconducting (SC) gap and electron-phonon coupling (EPC) strength, are largely unexplored experimentally. Here, we investigate the time-resolved ultrafast spectroscopy of a superconductor LaH10±δ under an ultrahigh pressure of 165 GPa. By analyzing the ultrafast dynamics of the quasiparticles, we experimentally obtain the SC gap Δ(0) = 53 ± 5 meV, revealing a gap ratio 2Δ(0)/k B T c = 5.6 and a gap parameter ϑ = 1.95. Significantly, we experimentally estimate $$\lambda \langle {\Omega }^{2}\rangle$$ λ ⟨ Ω 2 ⟩ = (2.4 ± 0.1) × 104 (meV)2, which corresponds to an EPC strength λ = 2.58 ± 0.11. These results together provide direct experimental evidence that strong EPC is responsible for the near-room-temperature superconductivity in clathrate superhydrides. Our investigation significantly advances the experimental exploration of superhydrides, and contributes to the ultrafast dynamics investigations of quantum materials under high pressures.

We synthesized polycrystalline La_{3}Ni_{2}O_{7−δ} (δ≈0.07) samples by using the sol-gel method without postannealing under high oxygen pressure, and then measured temperature-dependent resistivity under various hydrostatic pressures up to 18 GPa by using the cubic anvil and two-stage multianvil apparatus. We find that the density-wave-like anomaly in resistivity is progressively suppressed with increasing pressure and the resistivity drop corresponding to the onset of superconductivity emerges at pressure as low as ∼6 GPa. Zero resistivity is achieved at 9 GPa below T_{c}^{zero}≈6.6 K, which increases quickly with pressure to 41 K at 18 GPa. However, the diamagnetic response was not detected in the ac magnetic susceptibility measurements up to 15 GPa, indicating a filamentary nature of the observed superconductivity in the studied pressure range. The constructed T-P phase diagram reveals an intimate relationship between superconductivity, density-wave-like order, and the strange-metal-like behaviors. The observation of zero-resistance state in the polycrystalline La_{3}Ni_{2}O_{7−δ} samples under high pressures not only corroborates the recent report of superconductivity in the pressurized La_{3}Ni_{2}O_{7} crystals but also facilitates further studies on this emerging family of nickelate high-T_{c} superconductors.

The nature of unconventional charge density wave in kagome metals is currently under intense debate. Here the authors report the coexistence of the 2 × 2 × 1 charge density wave in the kagome sublattice and the Sb 5p-electron assisted 2 × 2 × 2 charge density waves in CsV3Sb5.

Despite much recent effort, the highest reported T c of the infinite-layer nickelates remains lower than 15 K. Here, the authors apply pressure to Pr0.82Sr0.18NiO2 thin films and observe a monotonic increase of T c to 31 K at 12.1 GPa, an increase that does not level off with increasing pressure.

Here, the authors report pressure-induced superconductivity with concomitant enhancement of antiferromagnetic transition in layered EuTe2. The superconductivity is distinctly characterized by the high upper critical fields exceeding the Pauli limit among binary tellurides, a prerequisite of the coexistence of ferromagnetism with superconductivity.