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Title: Extended Scattering Continua Characteristic of Spin Fractionalization in the Two-dimensional Frustrated Quantum Magnet Cs 2CuCl 4Observed by Neutron Scattering

Abstract

The magnetic excitations of the quasi-2D spin-1/2 frustrated Heisenberg antiferromagnet Cs{sub 2}CuCl{sub 4} are explored throughout the 2D Brillouin zone using high-resolution time-of-flight inelastic neutron scattering. Measurements are made both in the magnetically ordered phase, stabilized at low temperatures by the weak interlayer couplings, as well as in the spin liquid phase above the ordering temperature T{sub N}, when the 2D magnetic layers are decoupled. In the spin liquid phase the dynamical correlations are dominated by highly dispersive excitation continua, a characteristic signature of fractionalization of S = 1 spin waves into pairs of deconfined S = 1/2 spinons and the hallmark of a resonating-valence-bond (RVB) state. The boundaries of the excitation continua have strong 2D-modulated incommensurate dispersion relations. Upon cooling below T{sub N} magnetic order in an incommensurate spiral forms due to the 2D frustrated couplings. In this phase sharp magnons carrying a small part of the total scattering weight are observed at low energies, but the dominant continuum scattering which occurs at medium to high energies is essentially unchanged compared to the spin liquid phase. Linear spin-wave theory including one- and two-magnon processes can describe the sharp magnon excitation, but not the dominant continuum scattering, which instead ismore » well described by a parametrized two-spinon cross section. Those results suggest a crossover in the nature of the excitations from S = 1 spin waves at low energies to deconfined S = 1/2 spinons at medium to high energies, which could be understood if Cs{sub 2}CuCl{sub 4} was in the close proximity of transition between a fractional RVB spin liquid and a magnetically ordered state. A large renormalization factor of the excitation energies [R = 1.63(5)], indicating strong quantum fluctuations in the ground state, is obtained using the exchange couplings determined from saturation-field measurements. We provide an independent consistency check of this quantum renormalization factor using measurements of the second moment of the paramagnetic scattering.« less

Authors:
 [1];  [2];  [3]
  1. ORNL
  2. ISIS Facility, Rutherford Appleton Laboratory
  3. Adam Mickiewicz University, Poland
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); High Flux Isotope Reactor
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1003408
DOE Contract Number:  
DE-AC05-00OR22725
Resource Type:
Journal Article
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 68; Journal Issue: 13; Journal ID: ISSN 0163--1829
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ANTIFERROMAGNETIC MATERIALS; BRILLOUIN ZONES; CROSS SECTIONS; DISPERSION RELATIONS; EXCITATION; FLUCTUATIONS; GROUND STATES; MAGNETS; MAGNONS; NEUTRON DIFFRACTION; RENORMALIZATION; INELASTIC SCATTERING; SPIN; SPIN WAVES; TIME-OF-FLIGHT METHOD

Citation Formats

Coldea, Radu, Tennant, D. A., and Tyleczynski, Z. Extended Scattering Continua Characteristic of Spin Fractionalization in the Two-dimensional Frustrated Quantum Magnet Cs2CuCl4Observed by Neutron Scattering. United States: N. p., 2003. Web. doi:10.1103/PhysRevB.68.134424.
Coldea, Radu, Tennant, D. A., & Tyleczynski, Z. Extended Scattering Continua Characteristic of Spin Fractionalization in the Two-dimensional Frustrated Quantum Magnet Cs2CuCl4Observed by Neutron Scattering. United States. https://doi.org/10.1103/PhysRevB.68.134424
Coldea, Radu, Tennant, D. A., and Tyleczynski, Z. Wed . "Extended Scattering Continua Characteristic of Spin Fractionalization in the Two-dimensional Frustrated Quantum Magnet Cs2CuCl4Observed by Neutron Scattering". United States. https://doi.org/10.1103/PhysRevB.68.134424.
@article{osti_1003408,
title = {Extended Scattering Continua Characteristic of Spin Fractionalization in the Two-dimensional Frustrated Quantum Magnet Cs2CuCl4Observed by Neutron Scattering},
author = {Coldea, Radu and Tennant, D. A. and Tyleczynski, Z.},
abstractNote = {The magnetic excitations of the quasi-2D spin-1/2 frustrated Heisenberg antiferromagnet Cs{sub 2}CuCl{sub 4} are explored throughout the 2D Brillouin zone using high-resolution time-of-flight inelastic neutron scattering. Measurements are made both in the magnetically ordered phase, stabilized at low temperatures by the weak interlayer couplings, as well as in the spin liquid phase above the ordering temperature T{sub N}, when the 2D magnetic layers are decoupled. In the spin liquid phase the dynamical correlations are dominated by highly dispersive excitation continua, a characteristic signature of fractionalization of S = 1 spin waves into pairs of deconfined S = 1/2 spinons and the hallmark of a resonating-valence-bond (RVB) state. The boundaries of the excitation continua have strong 2D-modulated incommensurate dispersion relations. Upon cooling below T{sub N} magnetic order in an incommensurate spiral forms due to the 2D frustrated couplings. In this phase sharp magnons carrying a small part of the total scattering weight are observed at low energies, but the dominant continuum scattering which occurs at medium to high energies is essentially unchanged compared to the spin liquid phase. Linear spin-wave theory including one- and two-magnon processes can describe the sharp magnon excitation, but not the dominant continuum scattering, which instead is well described by a parametrized two-spinon cross section. Those results suggest a crossover in the nature of the excitations from S = 1 spin waves at low energies to deconfined S = 1/2 spinons at medium to high energies, which could be understood if Cs{sub 2}CuCl{sub 4} was in the close proximity of transition between a fractional RVB spin liquid and a magnetically ordered state. A large renormalization factor of the excitation energies [R = 1.63(5)], indicating strong quantum fluctuations in the ground state, is obtained using the exchange couplings determined from saturation-field measurements. We provide an independent consistency check of this quantum renormalization factor using measurements of the second moment of the paramagnetic scattering.},
doi = {10.1103/PhysRevB.68.134424},
url = {https://www.osti.gov/biblio/1003408}, journal = {Physical Review B},
issn = {0163--1829},
number = 13,
volume = 68,
place = {United States},
year = {2003},
month = {1}
}