Udupa, A and Sur, S and Nandy, S and Sen, A and Sen, D (2023) Weak universality, quantum manybody scars, and anomalous infinitetemperature autocorrelations in a onedimensional spin model with duality. In: Physical Review B, 108 (21).

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Abstract
We study a onedimensional spin1/2 model with threespin interactions and a transverse magnetic field h. The model is known to have a Z2Ã�Z2 symmetry and a duality between h and 1/h. The selfdual point at h=1 is a quantum critical point with a continuous phase transition. We compute the critical exponents z, Î², Î³, and Î½, and the central charge c numerically using exact diagonalization (ED) for systems with periodic boundary conditions. We find that both z and c are equal to 1, implying that the critical point is governed by a conformal field theory with a marginal operator. The values obtained for Î²/Î½, Î³/Î½, and Î½ from ED suggest that the model exhibits AshkinTeller criticality with an effective coupling that is intermediate between the fourstate Potts model and two decoupled transverse field Ising models. A more careful analysis on much larger systems but with open boundaries using densitymatrix renormalization group (DMRG) calculations, however, reveals important additive and multiplicative logarithmic corrections at and near criticality, and we present evidence that the selfdual point may be in the same universality class as the fourstate Potts model. An energy level spacing analysis shows that the model is not integrable. For a system with an even number of sites and periodic boundary conditions, there are exact midspectrum zeroenergy eigenstates whose number grows exponentially with the system size. A subset of these eigenstates have wave functions that are independent of the value of h and have unusual entanglement structures; hence these can be considered to be quantum manybody scars. The number of such quantum scars scales at least linearly with system size. Finally, we study the infinitetemperature autocorrelation functions at sites close to one end of an open system. We find that some of the autocorrelators relax anomalously in time, with pronounced oscillations and very small decay rates if hâ�«1 or hâ�ª1. If h is close to the critical point, the autocorrelators decay quickly to zero except for an autocorrelator at the end site. Â© 2023 American Physical Society.
Item Type:  Journal Article 

Publication:  Physical Review B 
Publisher:  American Physical Society 
Additional Information:  The copyright for this article belongs to Author. 
Keywords:  Autocorrelation; Boundary conditions; Criticality (nuclear fission); Ising model; Quantum entanglement; Statistical mechanics, Auto correlation; Autocorrelators; Exact diagonalization; Fourstate Potts model; Many body; Onedimensional; Periodic boundary conditions; Selfdual; Spin models; System size, Wave functions 
Department/Centre:  Others 
Date Deposited:  01 Mar 2024 09:56 
Last Modified:  01 Mar 2024 09:56 
URI:  https://eprints.iisc.ac.in/id/eprint/84020 
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