High-temperature superconductivity with zero resistance and strange-metal behaviour in La3Ni2O7−δ

Recent experimental observations have showed some signatures of superconductivity close to 80 K in La 3 Ni 2 O 7 under pressure and have raised the hope of achieving high-temperature superconductivity in bulk nickelates. However, a zero-resistance state—a key characteristic of a superconductor—was not observed. Here we show that the zero-resistance state does exist in single crystals of La 3 Ni 2 O 7− δ using a liquid pressure medium at up to 30 GPa. We also find that the system remains metallic under applied pressures, suggesting the absence of a metal–insulator transition proximate to the superconductivity. Moreover, analysis of the normal state T -linear resistance reveals a link between this strange-metal behaviour and superconductivity. The association between strange-metal behaviour and high-temperature superconductivity is very much in line with other classes of unconventional superconductors, including the cuprates and Fe-based superconductors. Further investigations exploring the interplay of strange-metal behaviour and superconductivity, as well as possible competing electronic or structural phases, are essential to understand the mechanism of superconductivity in this system. Some features resembling superconductivity at high temperature have been seen under pressure in La 3 Ni 2 O 7 , but a transition to a zero-resistance state has not been observed. Now transport studies demonstrate this transition, along with strange metallicity.