Pressure-induced quantum critical and multicritical points in a frustrated spin liquid

Abstract

The quantum spin-liquid compound (C4H12N2)Cu2Cl6 is studied by muon spin relaxation under hydrostatic pressures up to 23.6 kbar. At low temperatures, pressure-induced incommensurate magnetic order is detected beyond a quantum critical point at Pc∼4.3 kbar. An additional phase transition to a different ordered phase is observed at P1∼13.4 kbar. The data indicate that the high-pressure phase may be a commensurate one. The established (P-T) phase diagram reveals the corresponding pressure-induced multicritical point at P1, T1=2.0 K. © 2014 American Physical Society.