TY - JOUR

T1 - Dynamical mean-field theory for quantum spin systems

T2 - Test of solutions for magnetically ordered states

AU - Otsuki, Junya

AU - Kuramoto, Yoshio

PY - 2013/7/30

Y1 - 2013/7/30

N2 - A spin version of dynamical mean-field theory is extended for magnetically ordered states in the Heisenberg model. The self-consistency equations are solved with high numerical accuracy by means of the continuous-time quantum Monte Carlo with bosonic baths coupled to the spin. The resultant solution is critically tested by known physical properties. In contrast with the mean-field theory, soft paramagnons appear near the transition temperature. Moreover, the Nambu-Goldstone mode (magnon) in the ferromagnetic phase is reproduced reasonably well. However, antiferromagnetic magnons have an energy gap in contradiction to the Nambu-Goldstone theorem. The origin of this failure is discussed in connection with the artificial first-order nature of the transition.

AB - A spin version of dynamical mean-field theory is extended for magnetically ordered states in the Heisenberg model. The self-consistency equations are solved with high numerical accuracy by means of the continuous-time quantum Monte Carlo with bosonic baths coupled to the spin. The resultant solution is critically tested by known physical properties. In contrast with the mean-field theory, soft paramagnons appear near the transition temperature. Moreover, the Nambu-Goldstone mode (magnon) in the ferromagnetic phase is reproduced reasonably well. However, antiferromagnetic magnons have an energy gap in contradiction to the Nambu-Goldstone theorem. The origin of this failure is discussed in connection with the artificial first-order nature of the transition.

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U2 - 10.1103/PhysRevB.88.024427

DO - 10.1103/PhysRevB.88.024427

M3 - Article

AN - SCOPUS:84881124080

VL - 88

JO - Physical Review B - Condensed Matter and Materials Physics

JF - Physical Review B - Condensed Matter and Materials Physics

SN - 0163-1829

IS - 2

M1 - 024427

ER -