David K. Campbell

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n solid-state physics, the phenomenon of localization is usually perceived as arising from extrinsic disorder that breaks the discrete translational invariance of the perfect crystal lattice. Familiar examples include the localized vibrational phonon modes around impurities or defects (such as atomic vacancies or interstitial atoms) in crystals and Anderson(More)
Surface reactions with oxygen are a fundamental cause of the degradation of phosphorene. Using first-principles calculations, we show that for each oxygen atom adsorbed onto phosphorene there is an energy release of about 2 eV. Although the most stable oxygen adsorbed forms are electrically inactive and lead only to minor distortions of the lattice, there(More)
We calculate the dynamical spin structure factor of spin waves for weakly coupled stripes. At low energy, the spin-wave cone intensity is strongly peaked on the inner branches. As energy is increased, there is a saddlepoint followed by a square-shaped continuum rotated 45 degrees from the low energy peaks. This is reminiscent of recent high energy neutron(More)
We develop an asymptotically exact renormalization-group approach that treats electron-electron and electron-phonon interactions on an equal footing. The approach allows an unbiased study of the instabilities of Fermi liquids without the assumption of a broken symmetry. We apply our method to the problem of strongly coupled superconductors and find the(More)
We report three surprising results regarding the nature of the spatial broken symmetries in the two-dimensional ͑2D͒, quarter-filled band with strong electron-electron interactions that provides a microscopic model of the 2:1 cationic organic charge-transfer solids ͑CTS's͒. First, in direct contradiction to the predictions of one-electron theory, we find a(More)
The ground-state phase diagram of the half filled one-dimensional Holstein-Hubbard model contains a charge-density-wave ͑CDW͒ phase, driven by the electron-phonon ͑e-ph͒ coupling, and a spin-density-wave ͑SDW͒ phase, driven by the on-site electron-electron ͑e-e͒ repulsion. Recently, the existence of a third phase, which is metallic and lies in a finite(More)