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

Recently, the theoretically predicted lanthanum superhydride, LaH10 +/-delta, with a clathrate-like structure was successfully synthesized and found to exhibit a record high superconducting transition temperatureT(c)approximate to 250 K at similar to 170 GPa, opening a new route for room-temperature superconductivity. However, sincein situexperiments at megabar pressures are very challenging, few groups have reported the similar to 250 K superconducting transition in LaH10 +/-delta. 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 +/-delta)with dimensions up to 10 x 20 mu m(2)by laser heating a thin La flake and ammonia borane at similar to 1700 K in a symmetric diamond anvil cell under the pressure of 165 GPa. The superconducting transition atT(c)approximate to 250 K was confirmed through resistance measurements under various magnetic fields. Our method will facilitate explorations of near-room-temperature superconductors among metal superhydrides.