title: Inelastic light scattering measurements of a pressure-induced quantum liquid in KCuF3.
abstract: Pressure-dependent, low-temperature inelastic light (Raman) scattering measurements of KCuF(3) show that applied pressure above P* ~ 7 kbar suppresses a previously observed structural phase transition temperature to zero temperature in KCuF(3), resulting in the development of a fluctuational (quasielastic) response near T ~ 0 K. This pressure-induced fluctuational response--which we associate with slow fluctuations of the CuF(6) octahedral orientation--is temperature independent and exhibits a characteristic fluctuation rate that is much larger than the temperature, consistent with quantum fluctuations of the CuF(6) octahedra. A model of pseudospin-phonon coupling provides a qualitative description of both the temperature- and pressure-dependent evolution of the Raman spectra of KCuF(3).
authors.affiliation: Department of Physics and Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801, USA.
authors.forename: S
authors.initials: S
authors.lastname: Yuan
authors.forename: M
authors.initials: M
authors.lastname: Kim
authors.forename: J T
authors.initials: JT
authors.lastname: Seeley
authors.forename: J C T
authors.initials: JC
authors.lastname: Lee
authors.forename: S
authors.initials: S
authors.lastname: Lal
authors.forename: P
authors.initials: P
authors.lastname: Abbamonte
authors.forename: S L
authors.initials: SL
authors.lastname: Cooper