Unconventional Peierls physics in underdoped Bi2201

• Main Author: Rosen, Jonathan Adam
• Language: English
• Published: University of British Columbia 2012
• Online Access: http://hdl.handle.net/2429/43739

The puzzling physics of the high-temperature superconducting cuprates has led to many important questions and investigations regarding the mechanism of high-Tc's. This dissertation demonstrates that, through detailed experimental studies using angle-resolved photoemission (ARPES) and low-energy electron diffraction (LEED), a new type of periodic structural distortion exists in Bi₂Sr₂-xLaxCuO₆₊d (La-Bi2201), leading to the existence of multiple periodic lattice distortions (PLD) in the underdoped material. Photon-energy dependent ARPES reveals photoelectron diffraction effects that exhibit all relevant length scales as oscillations in the ARPES matrix element, leading to the observation of all of the diffraction-replica (DR) bands associated with the multiple PLD's. Furthermore, a charge-density-wave (CDW) associated with the new PLD at the crystal surface with a temperature-dependent wavelength is observed. A Ginzburg-Landau mean field model is shown to exhibit the same temperature-dependence from a combination of Fermi surface nesting and lattice commensurability affected by the temperature-dependent harmonic content of the CDW. A detailed temperature-dependence of the antinodal pseudogap reveals two simultaneous energy and temperature scales: one associated with the CDW, and the other in agreement with the magneto-optical Kerr effect and magnetic neutron diffraction results in the literature. Detailed nodal ARPES lineshapes reveal a peak in the real-part of the self-energy that coincides with band-crossing positions and the nodal ''kink'' energies for all dopings, providing evidence that these disparate features can be collectively explained by band hybridization allowed in the fully incommensurate crystal, which does not preserve parity. This provides one route to explain these phenomena - as a product of nested van-Hove singularities along the nodal line in underdoped La-Bi2201, which result in a Peierls distortion similar to the dichalcogenide CDW superconductors.