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

TL;DR

This paper critically examines the role of Fermi surface nesting in charge density wave formation, arguing that most CDWs are driven by electron-phonon interactions rather than nesting alone, and that the Peierls instability concept is often inapplicable to real materials.

Contribution

The study demonstrates that Fermi surface nesting rarely predicts CDW transitions accurately and highlights the importance of electron-phonon coupling in structural phase transitions.

Findings

Fermi surface nesting often does not match observed CDW wave vectors.

Most CDW transitions are driven by electron-phonon interactions, not nesting.

The Peierls instability concept is fragile and not generally applicable to real materials.

Abstract

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.