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海森堡Ladder模型中自旋波速度的理论研究

Numerical Study of the Spin-wave Velocity in Heisenberg Spin Ladder Model
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摘要 通过测量海森堡Ladder模型中不同链间相互作用Jv下的系统自旋波速度vs,并为此建立了海森堡Ladder模型,同时引入了弹性系数为K的链内弹性晶格,使Ladder模型形成了自发的柱状二聚化。在不同的Jv下,利用密度矩阵重整化群(DMRG)以及自洽方法,测量了不同尺寸系统其各自对应的单态与三重态之间的能隙G以及孤子宽度Ws,并将结果外推至热力学极限。通过对Ws-1/G斜率的测量,得到不同Jv下所对应的系统波速度vs。测量结果表明,伴随着G随Jv的增强而线性减弱的同时,Ws随着Jv的增强而非线性地快速增加,这使得vs发生了一个先减小后增大至无穷的连续变化,且随着K的增强这种变化愈发剧烈。这说明Jv对系统磁振子的扩散起到了抑制或促进作用。 The columnar - dimer Heisenberg spin ladder model is investigated to calculate the spin - wave velocity v under different in- terchain interaction J, conditions. The elastic lattice with the elastic force K is introduced into the system which induces spin chains unstable towards the spontaneous dimerization. We obtain the thermodynamic limitations of the singlet - triplet energy gap G and the soliton width We when the ladder model is in the Columnar Dimer state by Density - matrix Renormalization - group (DMRG) method and self- consistent method, v is obtained by measuring the slope of We -1/G. The numerical results show that, as J increases, G decreases linearly while We increases dramatically. According to this, v decreases at first and then increases to the infinite and this change becomes sharp when K is bigger. It is noticed that the interchain interaction J effects the magnon dispersion.
机构地区 同济大学
出处 《南昌航空大学学报(自然科学版)》 CAS 2012年第4期19-25,共7页 Journal of Nanchang Hangkong University(Natural Sciences)
基金 国家自然科学基金(10774112)
关键词 强关联 Ladder模型 密度矩阵重整化群 自旋波速度 strong correlation Ladder model DMRG spin - wave velocity
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