Large negative magnetoresistance and pseudogap phase in superconducting A15-type La${}_4$H${}_{23}$

Abstract

High pressure plays a crucial role in the field of superconductivity. Compressed hydride superconductors are leaders in the race for a material that can conduct electricity without resistance at high or even room temperature. In the present work, we have discovered new lanthanum superhydride, cubic A15-type La${}_4$H${}_{23}$, with lower stabilization pressure compared to the reported $\text{fcc}$ LaH${}_{10}$. Superconducting La${}_4$H${}_{23}$ was obtained by laser heating of LaH${}_3$ with ammonia borane at about 120 GPa. Transport measurements reveal the maximum critical temperature $\text{T}$${}_C$(onset) = 105 K and the critical field $\text{H}$${}_{C2}$(0) = 32 T at 118 GPa, as evidenced by the sharp drop of electrical resistance and the displacement of superconducting transitions in applied magnetic fields. Moreover, we provide evidence for unconventional transport associated with a pseudogap phase in La${}_4$H${}_{23}$ using pulsed magnetic fields up to 68 T. A large negative magnetoresistance in the non-superconducting state below 40 K, quasi $\text{T}$-linear electrical resistance, and a sign-change of its temperature dependence mark the emergence of pseudogap in this hydride. Discovered lanthanum hydride is a new member of the A15 family of superconductors with $\text{T}$${}_C$ exceeding the boiling point of liquid nitrogen.

A mistake in Figure 3(a) was fixed

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• Quasi Two-dimensional Vortex Matter in ThH${}_{10}$ Superhydride
• Ternary superhydrides under pressure of Anderson's theorem: Near-record superconductivity in (La,Sc)H${}_{12}$
• Reply to "Comment on `Nonstandard superconductivity or no superconductivity in hydrides under high pressure' "
• Observation of the Josephson effect in superhydrides: DC SQUID based on (La,Ce)H${}_{10+x}$ with operating temperature of 179 K
• Einstein and Debye temperatures, electron-phonon coupling constant and a probable mechanism for ambient-pressure room-temperature superconductivity in intercalated graphite