Longrange spin correlations in a honeycomb spin model with a magnetic field
Abstract
We consider the spin1/2 model on the honeycomb lattice [A. Kitaev, Ann. Phys. 321, 2 (2006)] in the presence of a weak magnetic field h _{α} ≪ J. Such a perturbation treated in the lowest nonvanishing order over h _{α} leads [K.S. Tikhonov, M.V. Feigel'man, and A.Yu. Kitaev, Phys. Rev. Lett. 106, 067203 (2011)] to a powerlaw decay of irreducible spin correlations 《 s ^{ z }( t, r) s ^{ z }(0, 0)》 ∝ h _{ z } ^{2} f( t, r), where f( t, r) ∝ [max( t, Jr)]^{4}. We have studied the effects of the next order of perturbation in h _{ z } and found an additional term of the order h _{ z } ^{4} in the correlation function 《 s ^{ z }( t, r) s ^{ z }(0, 0)》 which scales as h _{ z } ^{4} cosγ/ r ^{3} at Jt≪ r, where γ is the polar angle in the 2D plane. We demonstrate that such a contribution can be understood as a result of a perturbation of the effective Majorana Hamiltonian by the weak imaginary vector potential A _{ x } ∝ i h _{ z } ^{2}.
 Publication:

Soviet Journal of Experimental and Theoretical Physics Letters
 Pub Date:
 January 2016
 DOI:
 10.1134/S0021364016020090
 arXiv:
 arXiv:1610.04849
 Bibcode:
 2016JETPL.103..117L
 Keywords:

 Condensed Matter  Strongly Correlated Electrons
 EPrint:
 8 pages, 2 figures. Extended and corrected version of the paper published in JETP Lett. v.103, p.117 (2016)