Let probes excitations in a quantum Ising chain

Images showing magnetic behaviour from measurements on Let and Iris.

Top: magnetic behaviour at 7 T along the chain and two inter-chain directions measured on Let. Dashed lines show behaiour expected for a model of frustrated interchaining couplings. Bottom: 'Zeeman' ladder of bound states in zero field measured on Iris.
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The newly commissioned Let spectrometer on the ISIS Second Target Station, combined with the vertical-opening 9 T magnet and dilution refrigerator insert, offers unparalleled opportunities for probing atomic dynamics with high resolution and wide coverage in all three momentum directions.

We have used Let to explore the magnetic behaviour in CoNb2O6. We recently showed this material to be the first experimental realization of the much theoretically-studied Ising chain in transverse field. Here ‘quantum melting’ of order occurs above magnetic fields of 5.5 T, in which spontaneous long-range order is replaced by a gapped ‘quantum paramagnet.’ We have probed the magnetic behaviour in this high-field phase at 7 T along both interchain crystal directions and confirmed a model of frustrated interchain couplings. Knowing the strengths of these couplings is important as they are responsible for the formation of a ‘Zeeman’ ladder of confined bound states in zero field.

IM Cabrera, R Coldea (Oxford University), R Bewley, J Taylor (ISIS), D Prabhakaran (Oxford Univesity)

Research date: August 2011

Further Information

Contact: Dr R Coldea, r.coldea@physics.ox.ac.uk
Further reading: R Coldea et al., Science 327 (2010) 177

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