Charge-Density-Wave Order in 2H-NbSe${}_2$

Abstract

Competition between collective states like charge density wave and superconductivity is played out in some of the transition metal dichalcogenides unencumbered by the spin degrees of freedom. Although 2H-NbSe${}_2$ has received much less attention than some of the other members of the family (like 1T-TiSe${}_2$ and 2H-TaSe${}_2$), it shows superconductivity at 7.2 K and incommensurate charge ordering at 33 K. Recent experiments, notably Angle Resolved Photoemission spectroscopy, have cast serious doubts on the mechanism of Fermi surface nesting via electron-phonon interaction. The normal state has been found to be a poor, incoherent metal and remarkably, the coherence increases in the broken symmetry state. From a preformed excitonic liquid scenario, we show that there exists a natural understanding of the experimental data on 2H-NbSe${}_2$ based on electron-electron interaction. The collective instabilities, in this scenario, are viewed as a condensation of an incoherent excitonic liquid already present at high temperature.

7 pages, 10 figures. Shorter version appears in AIP Conf. Proc. 1461, 170 (2012)

References in corpus (14)

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• Preformed excitonic liquid route to a charge density wave in 2H-TaSe${}_2$

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• Pressure Driven Phase Transition in 1T-TiSe${}_2$ , a MOIPT+DMFT Study
• Phase Transition in IrTe${}_2$ induced by spin-orbit coupling
• Do Dynamical Excitonic Liquid Correlations Mediate Superconductivity in Elemental Bismuth?
• Transport properties of the parent LaNiO2