Electronic properties of doped Mott insulators and high temperature superconductors

High-temperature superconducting cuprates, which are the quintessential example of a strongly correlated system and the most extensively studied materials after semiconductors, spurred the development in the fields of material science and experimental and theoretical physics. As first noted by Anderson, these materials are doped Mott insulators and the novel phenomenology emerges in the regime intermediate to the Neel state and the Fermi liquid metal where electrons evolve from being local moments to itinerant entities. This thesis attempts to describe the evolution of the electronic properties between the above two limits as of interest to high-temperature superconductors. We use the tt't"J model to describe doped Mott insulators and resort to numerical methods and to both well known and new approximate analytical techniques to deal with the absence of on-site double electron occupancy. We first address the problem of a single hole in the tt't"J model in terms of the exact diagonalization and the self-consistent Born approximation methods. We show spins dress the doped hole in two distinct ways, namely with a staggered moment and a liquid spin configurations. The resulting two-band picture captures the momentum space anisotropy consistent with experimental observations in underdoped cuprates. Next we use the SU(2) slave boson mean-field theory of the tt'J model. The role of next-nearest-neighbor hopping t' on the phase diagram is studied. We find that when t' > 0.5J a Z2 state with true spin-charge separation exists, which can be a candidate for an eventual pseudogap phase in electron doped materials.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Physics.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2005

Author dc:creator

• Ribeiro, Tiago Castro

Advisor dc:contributor.advisor

• Xiao-Gang Wen.

• Physics.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/34383

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/34383