Exotic Phases in Low-Dimensional Quantum Magnets

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• Dr Christian Ruegg, UCL
• Thursday 10 December 2009, 13:45-15:00
• Theory Library.

If you have a question about this talk, please contact Dr Dimitri M Gangardt.

Quantum spins in magnets show a remarkable diversity of 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 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. These 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® (2009). [5] B. Thielemann et al., Phys. Rev. Lett. 102, 107204 (2009).

This talk is part of the Theoretical Physics Seminars series.

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