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Experimental confirmation of ballistic nanofriction and quasiparticle interference in Dirac materials.

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Date Issued:
2018
Abstract/Description:
This dissertation is broadly divided into two parts. The first part details the development and usage of an experimental apparatus to measure the dry nanofriction for a well-defined interface at high sliding speeds. I leverage the sensitivity of a quartz crystal microbalance (QCM) to determine the drag coefficient of an ensemble of gold nanocrystals sliding on graphene at speeds up to 11 cm/s. I discuss the theories of velocity-dependent friction, especially at high sliding speeds, and QCM modeling. I also discuss our synthesis protocols for graphene and molybdenum disulfide, as well as our protocol for fabricating a clean, graphene-laminated QCM device and nanocrystal ensemble. The design and fabrication of our QCM oscillator circuit is presented in detail. The quantitatively-measured the drag coefficient is compared against molecular dynamics simulations at both low and high sliding speeds. We show evidence of a predicted ultra-low friction regime and find that the interaction energy between gold nanocrystals and graphene is lower than previously assumed. In the second part of this dissertation, I detail the band structure measurement of a novel semimetal using scanning tunneling microscopy. In particular, I measured the energy-dependenceof quasiparticle interference patterns at the surface of zirconium silicon sulfide (ZrSiS), a topological nodal line semimetal whose charge carrier quasiparticles possess a pseudospin degree offreedom. The aims of this study were to (1) discover the shape of the band structure above the Fermi level along a high-symmetry direction, (2) discover the energetic location of the line node inthe same high-symmetry direction, and (3) discover the selection rules for k transitions. This study confirms the predicted linearity in E(k) of the band structure above the Fermi level. Additionally,we observe an energy-dependent mechanism for pseudospin scattering. This study also provides the first experimentally-derived estimation of the line node position in E(k).
Title: Experimental confirmation of ballistic nanofriction and quasiparticle interference in Dirac materials.
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Name(s): Lodge, Michael, Author
Ishigami, Masahiro, Committee Chair
Kaden, William, Committee Member
Schelling, Patrick, Committee Member
Del Barco, Enrique, Committee Member
Roy, Tania, Committee Member
University of Central Florida, Degree Grantor
Type of Resource: text
Date Issued: 2018
Publisher: University of Central Florida
Language(s): English
Abstract/Description: This dissertation is broadly divided into two parts. The first part details the development and usage of an experimental apparatus to measure the dry nanofriction for a well-defined interface at high sliding speeds. I leverage the sensitivity of a quartz crystal microbalance (QCM) to determine the drag coefficient of an ensemble of gold nanocrystals sliding on graphene at speeds up to 11 cm/s. I discuss the theories of velocity-dependent friction, especially at high sliding speeds, and QCM modeling. I also discuss our synthesis protocols for graphene and molybdenum disulfide, as well as our protocol for fabricating a clean, graphene-laminated QCM device and nanocrystal ensemble. The design and fabrication of our QCM oscillator circuit is presented in detail. The quantitatively-measured the drag coefficient is compared against molecular dynamics simulations at both low and high sliding speeds. We show evidence of a predicted ultra-low friction regime and find that the interaction energy between gold nanocrystals and graphene is lower than previously assumed. In the second part of this dissertation, I detail the band structure measurement of a novel semimetal using scanning tunneling microscopy. In particular, I measured the energy-dependenceof quasiparticle interference patterns at the surface of zirconium silicon sulfide (ZrSiS), a topological nodal line semimetal whose charge carrier quasiparticles possess a pseudospin degree offreedom. The aims of this study were to (1) discover the shape of the band structure above the Fermi level along a high-symmetry direction, (2) discover the energetic location of the line node inthe same high-symmetry direction, and (3) discover the selection rules for k transitions. This study confirms the predicted linearity in E(k) of the band structure above the Fermi level. Additionally,we observe an energy-dependent mechanism for pseudospin scattering. This study also provides the first experimentally-derived estimation of the line node position in E(k).
Identifier: CFE0007218 (IID), ucf:52222 (fedora)
Note(s): 2018-08-01
Ph.D.
Sciences, Physics
Doctoral
This record was generated from author submitted information.
Subject(s): ballistic nanofriction -- friction -- graphene -- quartz crystal microbalance -- QCM -- Dirac semimetal -- topological semimetal -- zirconium silicon sulfide -- ZrSiS -- scanning tunneling microscopy -- STM -- quasiparticle interference -- QPI -- Fourier-transform STM -- FT-STM -- spectroscopic imaging -- band structure measurement
Persistent Link to This Record: http://purl.flvc.org/ucf/fd/CFE0007218
Restrictions on Access: campus 2023-08-15
Host Institution: UCF

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