Abstract-Low-energy electrodynamics of novel spin excitations in the quantum spin ice Yb2Ti2O7

• • 
    
• LiDong Pan,
• Se Kwon Kim,
• A. Ghosh,
• Christopher M. Morris,
• Kate A. Ross,
• Edwin Kermarrec,
• Bruce D. Gaulin,
• S. M. Koohpayeh,
• Oleg Tchernyshyov
• & N. P. Armitage

• Affiliations
• Contributions
• Corresponding author

Nature Communications

 

5,

 

Article number:

 

4970

 

doi:10.1038/ncomms5970

Received

 

04 April 2014 

Accepted

 

12 August 2014 

Published

 

18 September 2014

http://www.nature.com/ncomms/2014/140918/ncomms5970/full/ncomms5970.html

In condensed matter systems, formation of long-range order (LRO) is often accompanied by new excitations. However, in many geometrically frustrated magnetic systems, conventional LRO is suppressed, while non-trivial spin correlations are still observed. A natural question to ask is then what is the nature of the excitations in this highly correlated state without broken symmetry? Frequently, applying a symmetry breaking field stabilizes excitations whose properties reflect certain aspects of the anomalous state without LRO. Here we report a THz spectroscopy study of novel excitations in quantum spin ice Yb2Ti2O7 under a <001> directed magnetic field. At large positive fields, both right- and left-handed magnon and two-magnon-like excitations are observed. The g-factors of these excitations are dramatically enhanced in the low-field limit, showing a crossover of these states into features consistent with the quantum string-like excitations proposed to exist in quantum spin ice in small <001> fields.