Lowenergy singlet sector in the spin1/2 J _{1} J _{2} Heisenberg model on a square lattice
Abstract
Based on a special variant of the plaquette expansion, an operator is constructed whose eigenvalues give the lowenergy singlet spectrum of a spin1/2 Heisenberg antiferromagnet on a square lattice with nearestheighbor and frustrating nextnearestneighbor exchange couplings J _{1} and J _{2}. It is well known that a nonmagnetic phase arises in this model for 0.4 ≲ J _{2}/ J _{1} ≲ 0.6, sandwiched by two Néel ordered phases. In agreement with previous results, we observe a firstorder quantum phase transition (QPT) at J _{2} ≈ 0.64 J _{1} from the nonmagnetic phase to the Néel one. A large gap (≳ 0.4 J _{1}) is found in the singlet spectrum for J _{2} < 0.64 J _{1}, which excludes a gapless spinliquid state for 0.4 ≲ J _{2}/ J _{1} ≲ 0.6 and the deconfined quantum criticality scenario for the QPT to another Néel phase. We observe a firstorder QPT at J _{2} ≈ 0.55 J _{1}, presumably between two nonmagnetic phases.
 Publication:

Soviet Journal of Experimental and Theoretical Physics
 Pub Date:
 December 2016
 DOI:
 10.1134/S1063776116150012
 arXiv:
 arXiv:1605.05152
 Bibcode:
 2016JETP..123.1035A
 Keywords:

 Condensed Matter  Strongly Correlated Electrons
 EPrint:
 J. Exp. Theor. Phys. (2016) 123: 1035