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arXiv 2104.14044cond-mat.str-el
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二维Peierls/Su-Schrieffer-Heeger极化子

Peierls/Su-Schrieffer-Heeger polarons in two dimensions

Chao Zhang, Nikolay V. Prokof'ev, Boris V. Svistunov

摘要:

具有不同类型的电子-声子耦合的极化子具有根本不同的性质。当电子密度和晶格位移之间的相互作用占主导地位时,基态的动量不发生变化,极化子在强耦合时变得指数重。相比之下,具有源自位移调制跳跃的相互作用的一维Peierls/Su-Schrieffer-Heeger(PSSH)极化子的特征在于,随着耦合增加,基态动量向有限值和有效质量的中等值的移位REF[Phys.Rev.Lett. 105,266605(2010)]。基于Diagrammatic Monte Carlo方法,我们研究了PSSH极化子的反常性质是否依赖于位移调制跳跃的类型,以及它们在高维中存活的程度。我们研究了两种不同的PSSH模型:玻色子自由度驻留在二维正方形晶格的网站(模型A)和债券(模型B)。对于模型A,我们发现在绝热和中间区域,基态的动量经历了一个从零到有限值的连续转变,作为耦合强度的函数。这种转变是由色散函数的二次不稳定性驱动的,这意味着有效质量在临界点发散,然后随着耦合的增加以各向异性的方式减小。出乎意料的是,对于模型B,基态的动量总是保持为零,有效质量随着耦合单调增加。这种增加远不是指数的,并且在强相互作用时趋于平稳,导致相对较轻的极化子。在强耦合状态下具有轻极化子对于高温超导性的双极化子机制是至关重要的REF[Phys. Rev. Lett. 121,247001(2018)]。

英文摘要:

Polarons with different types of electron-phonon coupling have fundamentally different properties. When the dominant interaction is between the electron density and lattice displacement, the momentum of the ground state does not change and the polaron gets exponentially heavy at strong coupling. In contrast, one-dimensional Peierls/Su-Schrieffer-Heeger (PSSH) polarons with interaction originating from displacement-modulated hopping feature a shift of the ground-state momentum to finite values and moderate values of effective mass as coupling is increased REF[Phys. Rev. Lett. 105, 266605 (2010)]. Based on Diagrammatic Monte Carlo method, we investigate whether unusual properties of PSSH polarons depend on the type of the displacement-modulated hopping and to what degree they survive in higher dimension. We study two different PSSH models: with bosonic degrees of freedom residing on sites (model A) and bonds (model B) of the two-dimensional square lattice. For model A, we find that in both adiabatic and intermediate regimes, the momentum of the ground state experiences a continuous transition from zero to a finite value as a function of coupling strength. The transition is driven by quadratic instability of the dispersion function, implying that effective mass diverges at the critical point, and then decreases in an anisotropic fashion with increasing coupling. Unexpectedly, for model B, the momentum of the ground state always stays at zero and the effective mass increases monotonously with coupling. The increase is far from exponential and tends to level-off at strong interaction, resulting in relatively light polarons. Having light polarons in the strong coupling regime is crucial for the bi-polaron mechanism of high-temperature superconductivity REF[Phys. Rev. Lett. 121, 247001 (2018)].

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