TY  - JOUR
AU  - Bera, A. K.
AU  - Lake, B.
AU  - Essler, F. H. L.
AU  - Vanderstraeten, L.
AU  - Hubig, C.
AU  - Schollwöck, U.
AU  - Islam, A. T. M. N.
AU  - Schneidewind, A.
AU  - Quintero-Castro, D. L.
TI  - Spinon confinement in a quasi-one-dimensional anisotropic Heisenberg magnet
JO  - Physical review / B
VL  - 96
IS  - 5
SN  - 2469-9950
CY  - Woodbury, NY
PB  - Inst.
M1  - FZJ-2017-06043
SP  - 054423
PY  - 2017
AB  - 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.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000407777600003
DO  - DOI:10.1103/PhysRevB.96.054423
UR  - https://juser.fz-juelich.de/record/837027
ER  -