Download Magnetic Field and Pressure Induced Quantum Phase Transitions in the... Liquid TlCuCl

Magnetic Field and Pressure Induced Quantum Phase Transitions in the Spin
Liquid TlCuCl3
Ch. Rüegga , A. Furrerb , K. Krämerc, H.-U. Güdelc , and H. Tanakad
a
London Centre for Nanotechnology, University College London, London WC1E 6BT, UK
Laboratory for Neutron Scattering, ETH Zurich, 5232 Villigen PSI, Switzerland
c
Department of Chemistry and Biochemistry, University of Bern, 3000 Bern 9, Switzerland
d
Department of Physics, Tokyo Institute of Technology, 152-8551 Tokyo, Japan
b
The generic low-temperature phase diagram of gapped dimer spin liquids is investigated by neutron
scattering in high magnetic fields and under hydrostatic pressure. The model compound TlCuCl 3 with
a non–magnetic singlet ground state (S = 0) shows quantum phase transitions at H c = 5.7 T and
pc = 1.07 kbar. The ground states above these transitions are characterized by condensates of magnetic
quasi-particles and result from a softening of the elementary triplet excitations (S = 1) by Zeeman
splitting in a magnetic field or by a pressure induced increase of the triplet bandwidth. We have measured
the parameter dependence of the excitation spectrum at ”T=0” across the quantum phase transitions as
well as at finite temperatures in the quantum critical region1 . The results will be discussed in the context
of magnetization plateaus and BEC of magnons as recently discovered in the related dimer-based spin
systems BaCuSi6 O6 , SrCu2 (BO3 )2 , and NH4 CuCl3 .
1
Ch. Rüegg et al., Nature 423, 62 (2003); Phys. Rev. Lett. 93, 037207 (2004); Phys. Rev. Lett. 93,
257201 (2004).
Sorting category: Ce Magnetism and properties of solids
Keywords: quantum phase transitions, neutron scattering, dimer spin systems, magnetic excitations
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