Regularly alternating spin-1/2 anisotropic XY chains: The ground-state and thermodynamic properties

Abstract

Using the Jordan-Wigner transformation and continued fractions we calculate rigorously the thermodynamic quantities for the spin-1/2 transverse Ising chain with periodically varying intersite interactions and/or on-site fields. We consider in detail the properties of the chains having a period of the transverse field modulation equal to 3. The regularly alternating transverse Ising chain exhibits several quantum phase transition points, where the number of transition points for a given period of alternation strongly depends on the specific set of the Hamiltonian parameters. The critical behavior in most cases is the same as for the uniform chain. However, for certain sets of the Hamiltonian parameters the critical behavior may be changed and weak singularities in the ground-state quantities appear. Due to the regular alternation of the Hamiltonian parameters the transverse Ising chain may exhibit plateau-like steps in the zero-temperature dependence of the transverse magnetization vs. transverse field and many-peak temperature profiles of the specific heat. We compare the ground-state properties of regularly alternating transverse Ising and transverse XX chains and of regularly alternating quantum and classical chains. Making use of the corresponding unitary transformations we extend the elaborated approach to the study of thermodynamics of regularly alternating spin-1/2 anisotropic XY chains without field. We use the exact expression for the ground-state energy of such a chain of period 2 to discuss how the exchange interaction anisotropy destroys the spin-Peierls dimerized phase.

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• Modular Many-Body Quantum Sensors
• Twisted Kitaev Bilayers and the Moiré Ising Model
• The anisotropic XY model on the inhomogeneous periodic chain
• The isotropic XY model on the inhomogeneous periodic chain
• Quantum phase transition of nonlocal Ising chain with transverse field in a resonator
• Quantum Phase Transitions in s=1/2 Ising Chain in a Regularly Alternating Transverse Field
• Spin-1/2 $XX$ chain in a transverse field with regularly alternating $g$-factors: Static and dynamic properties
• Quantum Ising model in a period-2 modulated transverse field
• Quantum Phase Transitions in Spin-1/2 Ising Chain in Regularly Alternating Transverse Field: Spin Correlation Functions
• Thermodynamic properties of the XX model in a chain with a period two and three coupling
• Fermionic Approach to Elementary Excitations and Magnetization Plateaus in an S=1/2 XX Hybrid Trimer-Dimer Chain