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arXiv 0708.1744cond-mat.mtrl-sci
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费米面嵌套与金属中电荷密度波的起源

Fermi surface nesting and the origin of Charge Density Waves in metals

M. D. Johannes, I. I. Mazin

摘要:

由费米面嵌套引起的CDW的概念起源于Peierls关于纯一维金属中电子不稳定性的想法,现在经常被应用于实际低维材料中的电荷有序。我们的想法是,如果费米面轮廓重合时,沿着观察到的CDW波矢量移动,那么CDW被认为是嵌套派生。我们表明,在大多数情况下,这个过程没有预测能力,因为费米面要么不嵌套在正确的波矢量,或嵌套更强烈地在错误的矢量。我们认为,只有一小部分,如果有的话,所观察到的电荷有序相变是真正的类似物的Peierls不稳定性,因为电子不稳定性很容易被破坏,即使是很小的偏差,从完美的嵌套条件。使用典型的CDW材料NbSe $_2$,TaSe $_2$,CeTe $_3$,我们表明,这样的条件几乎从来没有满足,和CDW相实际上是结构相变,由电子和离子子系统的协同作用,\textit{i.e.,} \textbf{q}依赖的电子-声子耦合起着不可或缺的一部分。我们还表明,数学上,原来的Peierls建设是如此脆弱,不太可能适用于真正的材料。我们认为,CDW和无公度晶格转变之间没有有意义的区别存在。

英文摘要:

The concept of a CDW induced by Fermi-surface nesting originated from the Peierls idea of electronic instabilities in purely 1D metals and is now often applied to charge ordering in real low-dimensional materials. The idea is that if Fermi surface contours coincide when shifted along the observed CDW wave vector, then the CDW is considered to be nesting-derived. We show that in most cases this procedure has no predictive power, since Fermi surfaces either do not nest at the right wave vector, or nest more strongly at the wrong vector. We argue that only a tiny fraction, if any, of the observed charge ordering phase transitions are true analogues of the Peierls instability because electronic instabilities are easily destroyed by even small deviations from perfect nesting conditions. Using prototypical CDW materials NbSe$_2$, TaSe$_2$, and CeTe$_3$, we show that such conditions are hardly ever fulfilled, and that the CDW phases are actually structural phase transitions, driven by the concerted action of electronic and ionic subsystems, \textit{i.e.,} \textbf{q}-dependent electron-phonon coupling plays an indispensable part. We also show mathematically that the original Peierls construction is so fragile as to be unlikely to apply to real materials. We argue that no meaningful distinction between a CDW and an incommensurate lattice transition exists.

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