Luttinger-Liquid Physics and Bose-Einstein Condensation in Quantum Magnets – Niels Bohr Institute - University of Copenhagen

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Luttinger-Liquid Physics and Bose-Einstein Condensation in Quantum Magnets

Luttinger-Liquid Physics and Bose-Einstein Condensation in Quantum Magnets

Dr Christian Rüegg
London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK

Quantum spins in magnets show a remarkable diversity of fascinating strongly correlated behaviour. Examples include clean realizations of magnetic quantum phase transitions (QPT) and generic quantum ground states as in Bose-Einstein Condensates (BEC), Luttinger-liquids, and spin supersolids [1]. Quantum fluctuations in such magnets are controlled efficiently by hydrostatic pressure, magnetic field, or chemical composition, leading to these complex novel states of matter. Magnetic insulators can therefore be used as model systems for spectroscopic investigations of quantum criticality and, in particular, the ground states of strongly interacting hardcore bosons, for which there are increasing parallels to ultra-cold atoms in optical lattices. I will present a number of fundamental pressure- and field-tuned QPTs [2-5] investigated by neutron scattering and bulk experimental techniques in a series of model materials, which cover both the effect of dimensionality and the degree of quasi-particle mobility. The results are discussed in the context of recent developments and future perspectives in neutron spectroscopy, quantum many-body theory, and crystal growth of novel custom-built metal-organic materials.

[1] T. Giamarchi, Ch. Rüegg, O. Tchernyshyov, Nature Physics 4, 198 (2008).
[2] Ch. Rüegg et al., Phys. Rev. Lett. 100, 205701 (2008).
[3] Ch. Rüegg et al., Phys. Rev. Lett. 101, 247202 (2008).
[4] B. Thielemann et al., Phys. Rev. B 79, 020408(R) (2009).
[5] B. Thielemann et al., Phys. Rev. Lett. 102, 107204 (2009).