Dislocations in stripes and lattice Dirac fermions

Mesaroš, A. (2010)

Doctoral Thesis

The central topic in this thesis is the effect of topological defects in two distinct types of condensed matter systems. The first type consists of graphene and topological insulators. By studying the long-range effect of lattice defects (dislocations and disclinations) we find that the graphene electrons mimic fundamental Dirac electrons in spaces with curvature and torsion. We show that these long-range effects influence interferometric transport measurements: (i) Emphasizing the importance of electron dephasing in graphene; (ii) Enabling a characterization of neutral Majorana states, which are important for quantum computation applications, and conjectured to exist in topological insulators. Considering also the microscopic structure of graphene dislocations, we interpret local tunneling experiments on graphite grain boundaries. The second type of systems we study are the high temperature cuprate superconductors, where the strongly interacting electrons lead to coexisting symmetry breaking orders in the pseudogap phase. We observe and describe the interplay of nematic (orientational) and stripe (translational) orderings in local tunneling experiments, with stripe dislocations playing the key role. We also describe the observed phonon anomaly in cuprates through the effect of metallic stripes.

• Dislocations
• Grain boundaries
• Graphene
• Majorana
• Nematic
• Pseudogap phase
• Stripes
• Torsion
• Zero modes

• All authors: Mesaroš, A.
• Supervisor: Zaanen, J.
• Qualification: Doctor (dr.)
• Awarding Institution: Faculty of Science, Leiden University
• Date: 2010-10-06
• Title of host publication: Casimir PhD Series
• ISBN (print): 9789085930860
• Name: 2010-20
• Court: LEI Universiteit Leiden