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Title: Studies of Dirac and Weyl fermions by angle resolved photoemission spectroscopy

Abstract

This dissertation consists of three parts. First, we study magnetic domains in Nd 2Fe 14B single crystals using high resolution magnetic force microscopy (MFM). In addition to the elongated, wavy nano-domains reported by a previous MFM study, we found that the micrometer size, star-shaped fractal pattern is constructed of an elongated network of nano-domains about 20 nm in width, with resolution-limited domain walls thinner than 2 nm. Second, we studied extra Dirac cones of multilayer graphene on SiC surface by ARPES and SPA-LEED. We discovered extra Dirac cones on Fermi surface due to SiC 6 x 6 and graphene 6√ 3 6√ 3 coincidence lattice on both single-layer and three-layer graphene sheets. We interpreted the position and intensity of the Dirac cone replicas, based on the scattering vectors from LEED patterns. We found the positions of replica Dirac cones are determined mostly by the 6 6 SiC superlattice even graphene layers grown thicker. Finally, we studied the electronic structure of MoTe 2 by ARPES and experimentally con rmed the prediction of type II Weyl state in this material. By combining the result of Density Functional Theory calculations and Berry curvature calculations with out experimental data, we identi ed Fermi arcs,more » track states and Weyl points, all features predicted to exist in a type II Weyl semimetal. This material is an excellent playground for studies of exotic Fermions.« less

Authors:
 [1]
  1. Iowa State Univ., Ames, IA (United States)
Publication Date:
Research Org.:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1342554
Report Number(s):
Is-T 3157
DOE Contract Number:  
AC02-07CH11358
Resource Type:
Thesis/Dissertation
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

Citation Formats

Huang, Lunan. Studies of Dirac and Weyl fermions by angle resolved photoemission spectroscopy. United States: N. p., 2016. Web. doi:10.2172/1342554.
Huang, Lunan. Studies of Dirac and Weyl fermions by angle resolved photoemission spectroscopy. United States. doi:10.2172/1342554.
Huang, Lunan. Fri . "Studies of Dirac and Weyl fermions by angle resolved photoemission spectroscopy". United States. doi:10.2172/1342554. https://www.osti.gov/servlets/purl/1342554.
@article{osti_1342554,
title = {Studies of Dirac and Weyl fermions by angle resolved photoemission spectroscopy},
author = {Huang, Lunan},
abstractNote = {This dissertation consists of three parts. First, we study magnetic domains in Nd2Fe14B single crystals using high resolution magnetic force microscopy (MFM). In addition to the elongated, wavy nano-domains reported by a previous MFM study, we found that the micrometer size, star-shaped fractal pattern is constructed of an elongated network of nano-domains about 20 nm in width, with resolution-limited domain walls thinner than 2 nm. Second, we studied extra Dirac cones of multilayer graphene on SiC surface by ARPES and SPA-LEED. We discovered extra Dirac cones on Fermi surface due to SiC 6 x 6 and graphene 6√ 3 6√ 3 coincidence lattice on both single-layer and three-layer graphene sheets. We interpreted the position and intensity of the Dirac cone replicas, based on the scattering vectors from LEED patterns. We found the positions of replica Dirac cones are determined mostly by the 6 6 SiC superlattice even graphene layers grown thicker. Finally, we studied the electronic structure of MoTe2 by ARPES and experimentally con rmed the prediction of type II Weyl state in this material. By combining the result of Density Functional Theory calculations and Berry curvature calculations with out experimental data, we identi ed Fermi arcs, track states and Weyl points, all features predicted to exist in a type II Weyl semimetal. This material is an excellent playground for studies of exotic Fermions.},
doi = {10.2172/1342554},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2016},
month = {1}
}

Thesis/Dissertation:
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