Pressure-Induced Color Change in the Lutetium Dihydride LuH₂

The lutetium dihydride LuH₂ is stable at ambient conditions. Here we show that its color undergoes sequential changes from dark blue at ambient pressure to pink at ∼ 2.2 GPa and then to bright red at ∼ 4 GPa upon compression in a diamond anvil cell. Such a pressure-induced color change in LuH₂ is reversible and it is very similar to that recently reported in the N-doped lutetium hydride Nature615, 244 (2023). However, our preliminary resistance measurements on LuH₂ under pressures up to ∼ 7 GPa evidenced no superconductivity down to 1.5 K.