掺杂对一维反铁磁海森堡自旋链性质的影响

应用三子格的自旋波理论和格林函数方法研究了由掺杂形成的准一维自旋1/2的反铁磁海森堡系统,得到系统存在3支自旋波激发谱,其中1支没有能隙,2支有能隙;在长波近似下,这3支自旋波激发谱与波矢k成平方关系,系统的低温比热为C∝T1/2关系,其基态具有磁性长程序,这都不同于未掺杂的一维自旋1/2的反铁磁海森堡链模型系统.对系统磁性序的研究表明,T=0是相变点,Mermin-Wagner定理对于该系统成立.

The effect of doping on the one dimensional antiferromagnetic Heisenberg model

By using spin- wave theory and Green function method,the quasi- one- dimensional antiferro- magnetic Heisenberg model in which side spins are added to the one dimensional chain is investigated. Three branches of excitation spectrum of the system are obtained.One is gapless and the other two are gapful.At the long- wave limit,three branches of the excitation spectrum behave like k2 .At low temperatures,the specific heat of the system behaves like T1/ 2 .The system studied has the magnetic long- range order in the ground state,but there is no long range order at finite temperatures.This means that the Mermin- Wagner theorem is still valid for the quasi- one- dimensional antiferromagnetic Heisenberg model studied in this paper.