Experimental studies of high-Tc cuprate superconductors with density wave correlations
- High-Tc cuprate superconductors remain the source of central intellectual challenges for condensed matter physicists two decades after their discovery. Accumulating evidence suggests possible ubiquity of coexisting superconducting and density wave correlations in the ground state of these materials. As both correlations in their spatiotemporally incoherent forms can in principle produce a pseudogap in the excitation spectrum, the nature of the pseudogap widely seen in cuprates above Tc comes to forefront of debate. I have been trying to address the relationship triangle between the pseudogap, superconductivity and density waves, by mainly using angle-resolved photoemission spectroscopy (ARPES) to study the momentum spaces of single-layer La-based (La214) and Bi-based (Bi2201) cuprates. In this thesis, I first talk about our ARPES-neutron scattering joint effort (in collaboration with Tohoku University) in the stripe-ordered state of La214. We found around the 1/8 doping level a dual nature of the pseudogap (in LBCO) and a dual nature of the spin stripe ordering ground state. The latter will be discussed in the context of a doping-dependent crossover between localized- and itinerant-spin ground-state physics, as demonstrated for the first time in a condensed matter system (1% Fe-doped LSCO). I then focus on our ARPES findings in both the pseudogap and superconducting states of nearly optimally-doped Pb-Bi2201 obtained over unprecedented momentum, energy and temperature ranges. They suggest that the pseudogap is a broken-symmetry state that is density-wave like and distinct from homogeneous superconductivity; it explicitly coexists with coherent superconductivity below Tc, causing a striking, momentum-dependent distortion of the high-Tc ground state. I also include in the appendix our recent observation of symmetry-distinct states (likely derived from the Cu dz orbital) in proximity to the Zhang-Rice singlet that has so far been generally taken as the only relevant electronic building block for cuprates. This finding might profoundly transform our upper-level understanding of high-Tc superconductivity as discussed above. This thesis ends with a chapter which describes my experimental philosophy, speculations and outlook for the near future of this field.
|Type of resource
|electronic; electronic resource; remote
|1 online resource.
|Stanford University, Department of Applied Physics
|Fisher, Ian R. (Ian Randal)
|Fisher, Ian R. (Ian Randal)
|Statement of responsibility
|Submitted to the Department of Applied Physics.
|Thesis (Ph.D.)--Stanford University, 2010.
- © 2010 by He Ruihua
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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