Superconductivity of Lanthanum Superhydride Investigated Using the Standard Four-Probe Configuration under High Pressures*

Abstract

Recently, the theoretically predicted lanthanum superhydride, LaH 10 ± δ , with a clathrate-like structure was successfully synthesized and found to exhibit a record high superconducting transition temperature T c ≈ 250 K at ∼ 170 GPa, opening a new route for room-temperature superconductivity. However, since in situ experiments at megabar pressures are very challenging, few groups have reported the ∼ 250 K superconducting transition in LaH 10 ± δ . Here, we establish a simpler sample-loading procedure that allows a relatively large sample size for synthesis and a standard four-probe configuration for resistance measurements. Following this procedure, we successfully synthesized LaH 10 ± δ with dimensions up to 10 × 20 μ m 2 by laser heating a thin La flake and ammonia borane at ∼ 1700 K in a symmetric diamond anvil cell under the pressure of 165 GPa. The superconducting transition at T c ≈ 250 K was confirmed through resistance measurements under various magnetic fields. Our method will facilitate explorations of near-room-temperature superconductors among metal superhydrides.