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- Title
Low-energy singlet sector in the spin-1/2 J - J Heisenberg model on a square lattice.
- Authors
Aktersky, A.; Syromyatnikov, A.
- Abstract
Based on a special variant of the plaquette expansion, an operator is constructed whose eigenvalues give the low-energy singlet spectrum of a spin- $$\frac{1}{2}$$ Heisenberg antiferromagnet on a square lattice with nearest-heighbor and frustrating next-nearest-neighbor exchange couplings J and J . It is well known that a nonmagnetic phase arises in this model for 0.4 ≲ J / J ≲ 0.6, sandwiched by two Néel ordered phases. In agreement with previous results, we observe a first-order quantum phase transition (QPT) at J ≈ 0.64 J from the non-magnetic phase to the Néel one. A large gap (≳ 0.4 J ) is found in the singlet spectrum for J < 0.64 J , which excludes a gapless spin-liquid state for 0.4 ≲ J / J ≲ 0.6 and the deconfined quantum criticality scenario for the QPT to another Néel phase. We observe a first-order QPT at J ≈ 0.55 J , presumably between two nonmagnetic phases.
- Subjects
HEISENBERG model; LATTICE field theory; NONMAGNETIC steel; PHASE transitions; QUANTUM phase transitions
- Publication
Journal of Experimental & Theoretical Physics, 2016, Vol 123, Issue 6, p1035
- ISSN
1063-7761
- Publication type
Article
- DOI
10.1134/S1063776116150012