In 2023, signatures of pressure-induced high-temperature superconductivity with an onset transition at 80 K were observed in La₃Ni₂O₇. However, the absence of zero resistance cast doubts on its superconductivity. By using a recently developed quasi-hydrostatic pressure technique based on a diamond anvil cell, our group successfully observe a sharp superconducting transition with a zero resistance below 40 K, providing a crucial evidence for establishing the existence of high-temperature superconductivity in La₃Ni₂O₇. Furthermore, a pronounced linear-temperature dependent resistivity is observed above its superconducting transition, suggesting an unconventional nature of its superconducting pairing state.

In addition to the discovery of zero resistance, our transport study also revises the pressure-temperature phase diagram of La₃Ni₂O₇. It is found that La₃Ni₂O₇ remains metallic under pressure and there is no evidence for a metal-insulator transition if the samples are properly handled during preparations. Upon increasing pressure, the density wave transition, observed near 130 K at ambient pressure, is quickly suppressed. At approximately 13.7 GPa, evidence for a pressure-induced structural phase transition is observed near 250 K, followed by a superconducting transition with an onset temperature at T_\mathrmc^\textonset\approx 37.5 K. T_\mathrmc initially increases with the increase of pressure, reaching a maximum value of T_\mathrmc^\textonset\approx 66 K at 20.5 GPa. On the other hand, the slope A' of the T-linear resistivity above T_\mathrmc monotonically decreases with the increase of pressure, showing a relation of T_\mathrmc\propto \sqrtA' above 20.5 GPa, which is similar to those recently observed in the cuprate superconductors. Furthermore, the inverse Hall coefficient 1/R_H, derived from the Hall resistance measurements, reveals a notable increase at pressures above 15 GPa upon entering the high pressure phase, suggesting a substantial increase of the carrier concentration in the superconducting regime, which is further supported by band structure calculations.

In this work, we present a brief summary of our research advances, and compare them with those observed in other nickelate superconductors.