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تسجيل مستخدم جديدCritical behavior of the quasi-periodic quantum Ising chain
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The interplay of correlated spatial modulation and symmetry breaking leads to quantum critical phenomena intermediate between those of the clean and randomly disordered cases. By performing a detailed analytic and numerical case study of the quasi-periodically (QP) modulated transverse field Ising chain, we provide evidence for the conjectures of Ref.~cite{crowley2018quasi} regarding the QP-Ising universality class. In the generic case, we confirm that the logarithmic wandering coefficient $w$ governs both the macroscopic critical exponents and the energy-dependent localisation length of the critical excitations. However, for special values of the phase difference $Delta$ between the exchange and transverse field couplings, the QP-Ising transition has different properties. For $Delta=0$, a generalised Aubry-Andre duality prevents the finite energy excitations from localising despite the presence of logarithmic wandering. For $Delta$ such that the fields and couplings are related by a lattice shift, the wandering coefficient $w$ vanishes. Nonetheless, the presence of small couplings leads to non-trivial exponents and localised excitations. Our results add to the rich menagerie of quantum Ising transitions in the presence of spatial modulation.
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