Quantum Monte Carlo calculation of the long-range order in the Heisenberg antiferromagnet.
نویسنده
چکیده
The forward-walking Green's function Monte Carlo (GFMC) method is used to compute the staggered magnetization m y in the two-dimensional, spin-1=2 Heisenberg Antifer-romagnet on L L square lattices, up to L = 12. Unlike previous GFMC calculations, the method is unbiased and projects out the exact, rotationally invariant groundstate. These calculations provide connrmation of the existence of long-range antiferromagnetic order in the groundstate. A known relationship between m y and the leading nite size correction, coupled with high precision groundstate energy calculations, is used to reduce the error in extrapolating to the thermodynamic limit. The data extrapolate to m y = :3075 :0025, only slightly diierent from the spin-wave theory result :3034. Several perfect singlet trial wavefunctions used to reduce the statistical error are discussed. A possible explanation as to why exact diagonalization extrapolations tend to yield low values of m y is presented.
منابع مشابه
Quantum Effects and Broken Symmetries in Frustrated Antiferromagnets
We investigate the interplay between frustration and zero-point quantum fluctuations in the ground state of the triangular and J1−J2 Heisenberg antiferromagnets, using finitesize spin-wave theory, exact diagonalization, and quantum Monte Carlo methods. In the triangular Heisenberg antiferromagnet, by performing a systematic size-scaling analysis, we have obtained strong evidences for a gapless ...
متن کاملDegeneracy and strong fluctuation-induced first-order phase transition in the dipolar pyrochlore antiferromagnet
We show that a continuous set of degenerate critical soft modes strongly enhances the first-order character of a fluctuation-induced first-order transition in the pyrochlore dipolar Heisenberg antiferromagnet. Such a degeneracy seems essential to explain the strong first-order transition recently observed in Gd2Sn2O7. We present some evidence from Monte Carlo simulations and a perturbative reno...
متن کاملOptimizing the RVB state on a triangular lattice: Presence of the long-range order
We present a Schwinger-boson approach for the RVB state of the spin-1/2 Heisenberg antiferromagnet on a triangular lattice. It is shown that a Gutzwiller projection of the mean-field state that includes both antiferromagnetic and ferromagnetic decouplings leads to optimizing the RVB pair amplitudes within a self-consistent approximation. The resulting state yields, by Monte Carlo simulations, e...
متن کاملDouble-layer Heisenberg antiferromagnet at finite temperature: Brueckner theory and quantum Monte Carlo simulations
The double-layer Heisenberg antiferromagnet with intraand inter-layer couplings J and J⊥ exhibits a zero temperature quantum phase transition between a quantum disordered dimer phase for g > gc and a Neel phase with long range antiferromagnetic order for g < gc, where g = J⊥/J and gc ≈ 2.5. We consider the behavior of the system at finite temperature for g ≥ gc using two different and complemen...
متن کاملحالت RVB بهینه در شبکه مربعی: حالت پایه و برانگیخته
We consider RVB state as a variational estimate for the ground state of Heisenberg antiferromagnet in square lattice. We present numerical calculation of energy, spin-spin correlation function and spin excitation spectrum. We show, that the quantum flactuations reduce of magnetization respect to Neel order. Our results are in good agreement with other methods such as spin-wave calculation a...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Physical review. B, Condensed matter
دوره 45 13 شماره
صفحات -
تاریخ انتشار 1992