一维电子-声子系统的非谐性
Anharmonicity in one-dimensional electron-phonon system
摘要：
利用行列式量子蒙特卡罗方法研究了一维半满Holstein模型中非谐性的影响。通过计算序参量，我们发现无论有无非谐性，都存在从无序相到二聚相的转变。此外，在二聚化相的晶格二聚化和电荷密度波共存。由四次项表示的非谐性抑制二聚以及电荷密度波，而双阱势有利于二聚。此外，通过计算相关指数，我们表明，无序相是金属与无隙电荷激发和有隙自旋激发，而在二聚相的激发都是有隙的。
英文摘要：
We investigate the effect of anharmonicity on the one-dimensional half-filled Holstein model by using the determinant quantum Monte Carlo method. By calculating the order parameters we find that with and without anharmonicity there is always an transition from a disorder phase to a dimerized phase. Moreover, in the dimerized phase a lattice dimerization and a charge density wave coexist. The anharmonicity represented by the quartic term suppresses the dimerization as well as the charge density wave, while a double-well potential favors the dimerization. In addition, by calculating the correlation exponents we show that the disorder phase is metallic with gapless charge excitations and gapful spin excitations while in the dimerized phase both excitations are gapful.
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