Journal Article

FZJ-2017-06043

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Spinon confinement in a quasi-one-dimensional anisotropic Heisenberg magnet

Bera, A. K. (Corresponding author) ; Lake, B. (Corresponding author) ; Essler, F. H. L. (Corresponding author) ; Vanderstraeten, L. ; Hubig, C. ; Schollwöck, U. ; Islam, A. T. M. N. ; Schneidewind, A.FZJ* ; Quintero-Castro, D. L.

2017
Inst. Woodbury, NY

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Please use a persistent id in citations: http://hdl.handle.net/2128/15275  doi:10.1103/PhysRevB.96.054423

Abstract: Confinement is a process by which particles with fractional quantum numbers bind together to formquasiparticles with integer quantum numbers. The constituent particles are confined by an attractive interactionwhose strength increases with increasing particle separation and, as a consequence, individual particles arenot found in isolation. This phenomenon is well known in particle physics where quarks are confined inbaryons and mesons. An analogous phenomenon occurs in certain spatially anisotropic magnetic insulators.These can be thought of in terms of weakly coupled chains of spins S = 1/2, and a spin flip thus carriesinteger spin S = 1. The collective excitations in these systems, called spinons, turn out to carry fractional spinquantum number S = 1/2. Interestingly, at sufficiently low temperatures the weak coupling between chains caninduce an attractive interaction between pairs of spinons that increases with their separation and thus leads toconfinement. In this paper, we employ inelastic neutron scattering to investigate the spinon-confinement processin the quasi-one-dimensional, spin-1/2 antiferromagnet with Heisenberg-Ising (XXZ) anisotropy SrCo2V2O8.A wide temperature range both above and below the long-range ordering temperature TN = 5.2 K is explored.Spinon excitations are observed above TN in quantitative agreement with established theory. Below TN pairs ofspinons are confined and two sequences of meson-like bound states with longitudinal and transverse polarizationsare observed. Several theoretical approaches are used to explain the data. These are based on a description interms of a one-dimensional, S = 1/2 XXZ antiferromagnetic spin chain, where the interchain couplings aremodeled by an effective staggered magnetic mean field. A wide range of exchange anisotropies are investigatedand the parameters specific to SrCo2V2O8 are identified. Recently developed theoretical technique based ontangent-space matrix product states gives a very complete description of the data and provides good agreementnot onlywith the energies of the bound modes but also with their intensities.We also successfully explain the effectof temperature on the excitations including the experimentally observed thermally induced resonance betweenlongitudinal modes below TN and the transitions between thermally excited spinon states above TN. In summary,our work establishes SrCo2V2O8 as a beautiful paradigm for spinon confinement in a quasi-one-dimensionalquantum magnet and provides a comprehensive picture of this process.

Keyword(s): Basic research (1st) ; Magnetism (2nd)

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Contributing Institute(s):

1. JCNS-FRM-II (JCNS (München) ; Jülich Centre for Neutron Science JCNS (München) ; JCNS-FRM-II)
2. Streumethoden (JCNS-2)

Research Program(s):

1. 6G15 - FRM II / MLZ (POF3-6G15) (POF3-6G15)
2. 6G4 - Jülich Centre for Neutron Research (JCNS) (POF3-623) (POF3-623)

Experiment(s):

1. PANDA: Cold three axes spectrometer (SR2)

Appears in the scientific report 2017

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Database coverage:
; ; ; Current Contents - Physical, Chemical and Earth Sciences ; Ebsco Academic Search ; IF < 5 ; JCR ; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection

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