双层Heisenberg反铁磁体中的量子相变

QUANTUM PHASE TRANSITION IN A BILAYER HEISENBERG ANTIFERROMAGNET

用键算符平均场方法研究了双层正方格子Ｈｅｉｓｅｎｂｅｒｇ 反铁磁体中的量子相变问题．得到的临界点以及低温下的量子临界行为符合相关的数值计算结果和非线性σ模型的结果．在数值计算不能达到的极低温度范围（ Ｔ≤０－３Ｊ１ ，Ｊ１ 为面内最近邻反铁磁交换作用） ，给出了量子临界行为的新证据．

In this paper we use a bond\|operator mean\|field theory to study the quantum phase transition in the bilayer Heisenberg antiferromagnet. The obtained critical point and low temperature quantum critical behavior are consistent with the numerical results and the nonlinear σ model results. In the very low temperature ( T≤0 3J\-1, J\-1 is the in\|plane antiferromagnetic coupling), where the numerical results are not available, present paper gives new evidence for the quantum critical behavior.