Quasiparticle Breakdown in a Quantum Spin Liquid
Abstract
Much of modern condensed matter physics is understood in terms of elementary excitations, or quasiparticles -- fundamental quanta of energy and momentum. Various strongly interacting atomic systems are successfully treated as a collection of quasiparticles with weak or no interactions. However, there are interesting limitations to this description: in some systems the very existence of quasiparticles cannot be taken for granted. Like unstable elementary particles, quasiparticles cannot survive beyond a threshold where certain decay channels become allowed by conservation laws; their spectrum terminates at this threshold. Such quasiparticle breakdown was first predicted for an exotic state of matter -- super-fluid {sup 4}He at temperatures close to absolute zero, a quantum Bose liquid where zero-point atomic motion precludes crystallization. Here we show, using neutron scattering, that quasiparticle breakdown can also occur in a quantum magnet and, by implication, in other systems with Bose quasiparticles. We have measured spin excitations in a two-dimensional quantum magnet, piperazinium hexachlorodicuprate (PHCC), in which spin-1/2 copper ions form a non-magnetic quantum spin liquid, and find remarkable similarities with excitations in superfluid {sup 4}He. We observe a threshold momentum beyond which the quasiparticle peak merges with the two-quasiparticle continuum. It then acquires a finite energy width andmore »
- Authors:
-
- ORNL
- Brookhaven National Laboratory (BNL)
- Johns Hopkins University
- Publication Date:
- Research Org.:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). High Flux Isotope Reactor (HFIR)
- Sponsoring Org.:
- USDOE Office of Science (SC)
- OSTI Identifier:
- 1003118
- DOE Contract Number:
- DE-AC05-00OR22725
- Resource Type:
- Journal Article
- Journal Name:
- Nature
- Additional Journal Information:
- Journal Volume: 440; Journal Issue: 7081; Journal ID: ISSN 0028--0836
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 74 ATOMIC AND MOLECULAR PHYSICS; BREAKDOWN; CONSERVATION LAWS; COPPER IONS; CRYSTALLIZATION; DECAY; ELEMENTARY PARTICLES; ENERGY; EXCITED STATES; HELIUM 4; INTERACTIONS; LIQUIDS; MAGNETS; MATTER; MOTION; NEUTRONS; SPECTRA; SPIN; SUPERCONDUCTORS; TRANSITION TEMPERATURE
Citation Formats
Stone, Matthew B, Zalinznyak, I., Hong, T., Broholm, C. L., and Reich, D. H. Quasiparticle Breakdown in a Quantum Spin Liquid. United States: N. p., 2006.
Web. doi:10.1038/nature04593.
Stone, Matthew B, Zalinznyak, I., Hong, T., Broholm, C. L., & Reich, D. H. Quasiparticle Breakdown in a Quantum Spin Liquid. United States. https://doi.org/10.1038/nature04593
Stone, Matthew B, Zalinznyak, I., Hong, T., Broholm, C. L., and Reich, D. H. 2006.
"Quasiparticle Breakdown in a Quantum Spin Liquid". United States. https://doi.org/10.1038/nature04593.
@article{osti_1003118,
title = {Quasiparticle Breakdown in a Quantum Spin Liquid},
author = {Stone, Matthew B and Zalinznyak, I. and Hong, T. and Broholm, C. L. and Reich, D. H.},
abstractNote = {Much of modern condensed matter physics is understood in terms of elementary excitations, or quasiparticles -- fundamental quanta of energy and momentum. Various strongly interacting atomic systems are successfully treated as a collection of quasiparticles with weak or no interactions. However, there are interesting limitations to this description: in some systems the very existence of quasiparticles cannot be taken for granted. Like unstable elementary particles, quasiparticles cannot survive beyond a threshold where certain decay channels become allowed by conservation laws; their spectrum terminates at this threshold. Such quasiparticle breakdown was first predicted for an exotic state of matter -- super-fluid {sup 4}He at temperatures close to absolute zero, a quantum Bose liquid where zero-point atomic motion precludes crystallization. Here we show, using neutron scattering, that quasiparticle breakdown can also occur in a quantum magnet and, by implication, in other systems with Bose quasiparticles. We have measured spin excitations in a two-dimensional quantum magnet, piperazinium hexachlorodicuprate (PHCC), in which spin-1/2 copper ions form a non-magnetic quantum spin liquid, and find remarkable similarities with excitations in superfluid {sup 4}He. We observe a threshold momentum beyond which the quasiparticle peak merges with the two-quasiparticle continuum. It then acquires a finite energy width and becomes indistinguishable from a leading-edge singularity, so that excited states are no longer quasiparticles but occupy a wide band of energy. Our findings have important ramifications for understanding excitations with gapped spectra in many condensed matter systems, ranging from band insulators to high-transition-temperature superconductors.},
doi = {10.1038/nature04593},
url = {https://www.osti.gov/biblio/1003118},
journal = {Nature},
issn = {0028--0836},
number = 7081,
volume = 440,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}