Modulations in the CuO chain layer of YBa2Cu3O7- delta : Charge density waves?

摘要: We have performed reversed-bias scanning tunneling microscopy at 20 K on the CuO chain layer of cold-cleaved single crystals $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$. find 1.3-nm corrugations which change sign under bias polarity reversal. This behavior and wavelength are in agreement with hypothesis that one-dimensional chains undergo a charge density wave transition. is first real-space evidence such transition also explore possibility caused by Friedel oscillations or bipolaron scattering. Several-nm depressions along transform into broad swells as voltage increased.