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Rotational symmetry breaking toward a string-valence bond solid phase in frustrated J1−J2 transverse field Ising model

Sadrzadeh, M ; Sharif University of Technology | 2018

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  1. Type of Document: Article
  2. DOI: 10.1016/j.physc.2018.02.008
  3. Publisher: Elsevier B.V , 2018
  4. Abstract:
  5. We study the effect of quantum fluctuations by means of a transverse magnetic field (Γ) on the highly degenerate ground state of antiferromagnetic J1−J2 Ising model on the square lattice, at the limit J2/J1=0.5. We show that harmonic quantum fluctuations based on single spin flips can not lift such degeneracy, however an-harmonic quantum fluctuations based on multi spin cluster flip excitations lift the degeneracy toward a unique ground state with string-valence bond solid (VBS) nature. A cluster operator formalism has been implemented to incorporate an-harmonic quantum fluctuations. We show that cluster-type excitations of the model lead not only to lower the excitation energy compared with a single-spin flip but also to lift the extensive degeneracy in favor of a string-VBS state, which breaks lattice rotational symmetry with only two fold degeneracy. The tendency toward the broken symmetry state is justified by numerical exact diagonalization. Moreover, we introduce a map to find the relation between the present model on the checkerboard and square lattices. © 2018 Elsevier B.V
  6. Keywords:
  7. Frustrated magnetism ; Valence bond solid ; Crystal lattices ; Excited states ; Ground state ; Harmonic analysis ; Ising model ; Quantum electronics ; Spin fluctuations ; Collective phenomena ; Exact diagonalization ; Frustrated magnetisms ; Quantum fluctuation ; Rotational symmetries ; Transverse magnetic field ; Transverse-field Ising model ; Valence-bond solids ; Quantum theory
  8. Source: Physica C: Superconductivity and its Applications ; Volume 549 , 2018 , Pages 1-3 ; 09214534 (ISSN)
  9. URL: https://www.sciencedirect.com/science/article/abs/pii/S0921453417302368