Excitation spectrum of Heisenberg spin ladders
Abstract
Heisenberg antiferromagnetic spin ladders'' (two coupled spin chains) are lowdimensional magnetic systems which for [ital S]=1/2 interpolate between halfintegerspin chains, when the chains are decoupled, and effective integerspin onedimensional chains in the strongcoupling limit. The spin1/2 ladder may be realized in nature by vanadyl pyrophosphate, (VO)[sub 2]P[sub 2]O[sub 7]. In this paper we apply strongcoupling perturbation theory, spinwave theory, Lanczos techniques, and a Monte Carlo method to determine the groundstate energy and the lowlying excitation spectrum of the ladder. We find evidence of a nonzero spin gap for [ital all] interchain couplings [ital J][sub [perpendicular]][gt]0. A band of spintriplet excitations above the gap is also analyzed. These excitations are unusual for an antiferromagnet, since their longwavelength dispersion relation behaves as ([ital k][minus][ital k][sub 0])[sup 2] (in the strongcoupling limit [ital J][sub [perpendicular]][much gt][ital J], where [ital J] is the inchain antiferromagnetic coupling). Their band is folded, with a minimum energy at [ital k][sub 0]=[pi], and a maximum between [ital k][sub 1]=[pi]/2 (for [ital J][sub [perpendicular]]=0) and 0 (for [ital J][sub [perpendicular]]=[infinity]). We also give numerical results for the dynamical structure factor [ital S]([ital q],[omega]), which can be determined in neutron scattering experiments. Finally, possible experimental techniques for studying the excitationmore »
 Authors:

 Physics Division and Center for Computationally Intensive Physics, Oak Ridge National Laboratory, Oak Ridge, Tennessee 378316373 (United States) Department of Physics, University of Tennessee, Knoxville, Tennessee 379961200 (United States)
 Department of Physics, Center for Materials Research and Technology and Supercomputer Computations Research Institute, Florida State University, Tallahassee, Florida 32306 (United States)
 Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
 Publication Date:
 OSTI Identifier:
 6941912
 DOE Contract Number:
 FG0591ER40627
 Resource Type:
 Journal Article
 Journal Name:
 Physical Review, B: Condensed Matter; (United States)
 Additional Journal Information:
 Journal Volume: 47:6; Journal ID: ISSN 01631829
 Country of Publication:
 United States
 Language:
 English
 Subject:
 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; HEISENBERG MODEL; EXCITED STATES; ANTIFERROMAGNETISM; COUPLING; ENERGY GAP; MONTE CARLO METHOD; PERTURBATION THEORY; SPIN WAVES; STRONGCOUPLING MODEL; VANADIUM PHOSPHATES; CALCULATION METHODS; CRYSTAL MODELS; ENERGY LEVELS; MAGNETISM; MATHEMATICAL MODELS; OXYGEN COMPOUNDS; PARTICLE MODELS; PHOSPHATES; PHOSPHORUS COMPOUNDS; TRANSITION ELEMENT COMPOUNDS; VANADIUM COMPOUNDS; 665000*  Physics of Condensed Matter (1992)
Citation Formats
Barnes, T, Dagotto, E, Riera, J, and Swanson, E S. Excitation spectrum of Heisenberg spin ladders. United States: N. p., 1993.
Web. doi:10.1103/PhysRevB.47.3196.
Barnes, T, Dagotto, E, Riera, J, & Swanson, E S. Excitation spectrum of Heisenberg spin ladders. United States. https://doi.org/10.1103/PhysRevB.47.3196
Barnes, T, Dagotto, E, Riera, J, and Swanson, E S. Mon .
"Excitation spectrum of Heisenberg spin ladders". United States. https://doi.org/10.1103/PhysRevB.47.3196.
@article{osti_6941912,
title = {Excitation spectrum of Heisenberg spin ladders},
author = {Barnes, T and Dagotto, E and Riera, J and Swanson, E S},
abstractNote = {Heisenberg antiferromagnetic spin ladders'' (two coupled spin chains) are lowdimensional magnetic systems which for [ital S]=1/2 interpolate between halfintegerspin chains, when the chains are decoupled, and effective integerspin onedimensional chains in the strongcoupling limit. The spin1/2 ladder may be realized in nature by vanadyl pyrophosphate, (VO)[sub 2]P[sub 2]O[sub 7]. In this paper we apply strongcoupling perturbation theory, spinwave theory, Lanczos techniques, and a Monte Carlo method to determine the groundstate energy and the lowlying excitation spectrum of the ladder. We find evidence of a nonzero spin gap for [ital all] interchain couplings [ital J][sub [perpendicular]][gt]0. A band of spintriplet excitations above the gap is also analyzed. These excitations are unusual for an antiferromagnet, since their longwavelength dispersion relation behaves as ([ital k][minus][ital k][sub 0])[sup 2] (in the strongcoupling limit [ital J][sub [perpendicular]][much gt][ital J], where [ital J] is the inchain antiferromagnetic coupling). Their band is folded, with a minimum energy at [ital k][sub 0]=[pi], and a maximum between [ital k][sub 1]=[pi]/2 (for [ital J][sub [perpendicular]]=0) and 0 (for [ital J][sub [perpendicular]]=[infinity]). We also give numerical results for the dynamical structure factor [ital S]([ital q],[omega]), which can be determined in neutron scattering experiments. Finally, possible experimental techniques for studying the excitation spectrum are discussed.},
doi = {10.1103/PhysRevB.47.3196},
url = {https://www.osti.gov/biblio/6941912},
journal = {Physical Review, B: Condensed Matter; (United States)},
issn = {01631829},
number = ,
volume = 47:6,
place = {United States},
year = {1993},
month = {2}
}