Charge-density-wave structure and a metal-insulator transition inCrxNbSe3detected by atomic force microscopy and transport measurements

The addition of Cr to ${\mathrm{NbSe}}_3$ at low concentrations reduces the charge-density-wave energy gaps and modifies the Fermi surface. As the concentration is increased to 5 at. % a new phase exhibiting a metal-insulator transition at ∼700 K is formed. Atomic force microscopy shows a strong static charge modulation with a wavelength of three times the atomic spacing and the crystal is completely insulating at room temperature.