Mena, M.; Hanni, N.; Ward, S.; Hirtenlechner, E.; Bewley, R.; Hubig, C.; Schollwock, U.; Normand, B.; Kramer, K. W.; McMorrow, D. F.; Ruegg, Ch
(2020):
Thermal Control of Spin Excitations in the Coupled IsingChain Material RbCoCl3.
In: Physical Review Letters, Vol. 124, No. 25, 257201

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Abstract
We have used neutron spectroscopy to investigate the spin dynamics of the quantum (S = 1/2) antiferromagnetic Ising chains in RbCoCl3. The structure and magnetic interactions in this material conspire to produce two magnetic phase transitions at low temperatures, presenting an ideal opportunity for thermal control of the chain environment. The highresolution spectra we measure of twodomainwall excitations therefore characterize precisely both the continuum response of isolated chains and the "Zeemanladder" bound states of chains in three different effective staggered fields in one and the same material. We apply an extended Matsubara formalism to obtain a quantitative description of the entire dataset, Monte Carlo simulations to interpret the magnetic order, and finitetemperature densitymatrix renormalizationgroup calculations to fit the spectral features of all three phases.