arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 0907.3751cond-mat.str-el
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Hubbard-Holstein模型中的竞争相互作用和对称性破缺

Competing interactions and symmetry breaking in the Hubbard-Holstein model

Johannes Bauer

摘要:

在相关电子系统中,相互竞争的相互作用常常是引起有趣的相图的原因。本文分析了瞬时短程库仑相互作用$U$与Hubbard-Holstein模型描述的电子-声子耦合$g$引起的延迟电子-电子相互作用的竞争。建立了该模型在大尺寸极限下的半填充状态下的基态相图。研究是基于动力学平均场理论结合数值重整化群。根据$U$、$g$和声子频率$ω_0$,基态是反铁磁的(AFM)或电荷有序的(CO)。我们发现当$U-λ\simeq 0$,其中$λ$表征声子诱导的有效吸引力时,从AFM到CO态的量子相变发生。对于小的耦合和大的声子频率$ω_0$,跃迁是连续的,而对于大的耦合和小的$ω_0$值,跃迁变得不连续。我们评论这项工作可能的相关性Ba ${}_{1-x}$ K ${}_x$生物${}_3$。

英文摘要:

Competing interactions are often responsible for intriguing phase diagrams in correlated electron systems. Here we analyze the competition of instantaneous short range Coulomb interaction $U$ with the retarded electron-electron interaction induced by an electron-phonon coupling $g$ as described by the Hubbard-Holstein model. The ground state phase diagram of this model in the limit of large dimensions at half filling is established. The study is based on dynamical mean field theory combined with the numerical renormalization group. Depending on $U$, $g$, and the phonon frequency $ω_0$, the ground state is antiferromagnetically (AFM) or charge ordered (CO). We find quantum phase transitions from the AFM to CO state to occur when $U-λ\simeq 0$, where $λ$ characterizes the phonon induced effective attraction. The transition is continuous for small couplings and large phonon frequencies $ω_0$ and becomes discontinuous for large couplings and small values of $ω_0$. We comment on the possible relevance of this work for Ba${}_{1-x}$K${}_x$BiO${}_3$.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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