Quantum magnetism and quantum phase transitions

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Quantum criticality in an Ising chain: experimental evidence for emergent E8 symmetry

(2011)

Authors:

R Coldea, DA Tennant, EM Wheeler, E Wawrzynska, D Prabhakaran, M Telling, K Habicht, P Smeibidl, K Kiefer
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Anomalous high-energy spin excitations in the high-Tc superconductor-parent antiferromagnet La₂CuO₄.

Phys Rev Lett 105:24 (2010) 247001

Authors:

NS Headings, SM Hayden, R Coldea, TG Perring

Abstract:

Inelastic neutron scattering is used to investigate the collective magnetic excitations of the high-temperature superconductor-parent antiferromagnet La2CuO4. We find that while the lower energy excitations are well described by spin-wave theory, including one- and two-magnon scattering processes, the high-energy spin waves are strongly damped near the (1/2, 0) position in reciprocal space and merge into a momentum dependent continuum. This anomalous damping indicates the decay of spin waves into other excitations, possibly unbound spinon pairs.
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Anomalous High-Energy Spin Excitations in La2CuO4

(2010)

Authors:

NS Headings, SM Hayden, R Coldea, TG Perring
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Direct observation of charge order in triangular metallic AgNiO2 by single-crystal resonant X-ray scattering

(2010)

Authors:

GL Pascut, R Coldea, PG Radaelli, A Bombardi, G Beutier, II Mazin, MD Johannes, M Jansen
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Magnetoacoustics of the low-dimensional quantum antiferromagnet Cs 2CuCl 4 with spin frustration

Journal of Low Temperature Physics 159:1-2 (2010) 109-113

Authors:

A Sytcheva, O Chiatti, J Wosnitza, S Zherlitsyn, AA Zvyagin, R Coldea, Z Tylczynski

Abstract:

We report on results of sound-velocity and sound-attenuation measurements in the triangular-lattice spin-1/2 antiferromagnet Cs 2CuCl 4 (T N =0.6 K), in external magnetic fields up to 14 T, applied along the b axis, and at temperatures down to 300 mK. The results are analyzed with a quasi-two-dimensional hard-core boson theory based on exchange-striction coupling. There is a good qualitative agreement between theoretical and experimental results.
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