Pressure-Induced Magnetic Quantum Phase Transition in Gapped Spin System KCuCl₃

Abstract

Magnetization and neutron elastic scattering measurements under a hydrostatic\npressure were performed on KCuCl3, which is a three-dimensionally coupled spin\ndimer system with a gapped ground state. It was found that an intradimer\ninteraction decreases with increasing pressure, while the sum of interdimer\ninteractions increases. This leads to the shrinkage of spin gap. A quantum\nphase transition from a gapped state to an antiferromagnetic state occurs at Pc\n? 8.2 kbar. For P > P c, magnetic Bragg reflections were observed at reciprocal\nlattice points equivalent to those for the lowest magnetic excitation at zero\npressure. This confirms that the spin gap decreases and closes under applied\npressure.\n