Pressure-induced melting of magnetic order and emergence of a new quantum state in alpha-RuCl3

Here we report the observation of pressure-induced melting of antiferromagnetic (AFM) order and the emergence of a new state in the honeycomb-lattice halide alpha-RuCl3, a candidate compound in the proximity of quantum spin liquid state. Our high-pressure heat capacity measurements demonstrate that the AFM order smoothly melts away at a critical pressure (Pc) below 1 GPa. Intriguingly, the AFM transition temperature displays an increase upon applying pressure below the P(c,)in stark contrast to usual phase diagrams, for example, in pressurized parent compounds of unconventional superconductors. Furthermore,a stable magnetoresistance is observed in the high-pressure phase above P-c which is robust against pressure up to similar to 140 GPa.