The recent report of pressure-induced structure transition and signature of
superconductivity with Tc = 80 K above 14 GPa in the La3Ni2O7 crystals has
garnered considerable attention. To further elaborate this discovery, we
carried out comprehensive resistance measurements on the La3Ni2O7 crystals
grown with the optical-image floating zone furnace under oxygen pressure (15
bar) by using the diamond anvil cell (DAC) and cubic anvil cell (CAC), which
employs the solid and liquid pressure transmitting medium, respectively. For
the sample #1 measured in DAC, it exhibits a semiconducting-like behavior with
large resistance at low pressures and becomes metallic gradually upon
compression. At the pressures P >= 13.7 GPa, we observed the appearance of
resistance drop as large as ~50% around 70 K, which evolves into a kink-like
anomaly at pressures above 40 GPa and shifts to lower temperatures gradually
with increasing magnetic field. These observations are consistent with the
recent report mentioned above. On the other hand, the sample #2 measured in CAC
retains the metallic behavior in the investigated pressure range up to 15 GPa.
The hump-like anomaly in resistance around ~130 K at ambient pressure
disappears at P >= 2 GPa. In the pressure range from 11 to 15 GPa, we observed
the gradual development of a shoulder-like anomaly in resistance at low
temperatures, which evolves into a pronounced drop of resistance by 98% below
62 K at 15 GPa, reaching a temperature-independent resistance of 20 uOhm below
20 K. Similarly, this resistance anomaly can be shifted to lower temperatures
progressively by applying external magnetic fields, resembling a typical
superconducting transition.Comment: 4 Figure