Metallization of Cu₃N semiconductor under high pressure

Using the four-probe method, we investigate the electrical conductivity of Cu₃N under high pressure with the diamond anvil cell. Cu ₃N is a semiconductor at ambient pressure showing a band gap about 1 eV. With the application of quasi-hydrostatic pressures, its resistance decreases dramatically over five orders of magnitude from ambient to 9 GPa. The compound became a metal at pressure about 5.5 GPa, which is in well agreement with the recent first principle calculation.