Department of Physics, Stanford University, Stanford, California 94305, USA.
Phys Rev Lett. 2012 Dec 14;109(24):246404. doi: 10.1103/PhysRevLett.109.246404. Epub 2012 Dec 10.
We present a determinant quantum Monte Carlo study of the competition between instantaneous on-site Coulomb repulsion and retarded phonon-mediated attraction between electrons, as described by the two-dimensional Hubbard-Holstein model. At half filling, we find a strong competition between antiferromagnetism (AFM) and charge-density-wave (CDW) order. We demonstrate that a simple picture of AFM-CDW competition that incorporates the phonon-mediated attraction into an effective-U Hubbard model requires significant refinement. Specifically, retardation effects slow the onset of charge order so that CDW order remains absent even when the effective U is negative. This delay opens a window where neither AFM nor CDW order is well established and where there are signatures of a possible metallic phase.
我们提出了一个二维 Hubbard-Holstein 模型的决定论量子蒙特卡罗研究，该模型描述了电子之间的瞬时局域库仑排斥和延迟声子介导的吸引之间的竞争。在半填充情况下，我们发现反铁磁（AFM）和电荷密度波（CDW）有序之间存在强烈的竞争。我们证明，将声子介导的吸引纳入有效-U Hubbard 模型的简单 AFM-CDW 竞争图像需要进行重大改进。具体来说，延迟效应会减缓电荷有序的出现，以至于即使有效 U 为负，CDW 有序仍然不存在。这种延迟为一个可能的金属相打开了一个窗口，在这个窗口中，AFM 或 CDW 有序都没有得到很好的建立，并且存在可能的金属相的特征。
