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Study of two dimensional materials graphene and FeSe Yang, Rui
Abstract
The properties of several two-dimensional (2d) materials are studied. The main content is the study of magnetic impurities in graphene through phase coherent transport phenomena, including weak localization (WL) and universal conductance fluctuations (UCF). Magnetic impurities manifest themselves in the in-plane magnetic field and temperature dependence of the dephasing (phase breaking) rate. Our experiments unambiguously reveal the existence of magnetic impurities through the in-plane magnetic field dependence of WL and UCF. The properties of the magnetic impurities are further studied through the dephasing rate as a function of magnetic field and temperature. The WL dephasing rate as a function of in-plane magnetic field shows a non-monotonic behaviour, which is rooted in the existence of magnetic impurities with a Landé g factor different from that of the free electron. The collapse of the dephasing rate as a function of temperature is a sign of the quenching of magnetic impurities, which could come from Kondo coupling between magnetic impurities and conduction electrons or Ruderman-Kittel-Kasuya-Yosida (RKKY) coupling between magnetic impurities. The implications of our graphene experiments are two-fold: on the one hand, they provide new knowledge about the interplay among magnetic moments and electrons in graphene; on the other hand, they also established an effective tool to reveal the existence of magnetic impurities in 2d systems. In addition to graphene, we also studied the exfoliation and stability of thin sheets of FeSe -- a member of the Fe-based superconductors family. Our Raman Spectroscopy, Atomic Force Microscopy, Optical Microscopy and Time-of-Flight-Secondary-Ion-Mass-Spectroscopy experiments show that FeSe nanosheets decay in air, precipitation of Se and oxidation likely occurring during the decay process. Our transport measurements show that FeSe nanosheets exposed briefly to air can still retain superconductivity.
Item Metadata
Title |
Study of two dimensional materials graphene and FeSe
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2018
|
Description |
The properties of several two-dimensional (2d) materials are studied. The
main content is the study of magnetic impurities in graphene through phase
coherent transport phenomena, including weak localization (WL) and universal
conductance fluctuations (UCF). Magnetic impurities manifest themselves
in the in-plane magnetic field and temperature dependence of the dephasing (phase breaking) rate. Our experiments unambiguously reveal
the existence of magnetic impurities through the in-plane magnetic field dependence of WL and
UCF. The properties of the magnetic impurities are further studied through
the dephasing rate as a function of magnetic field and temperature. The
WL dephasing rate as a function of in-plane magnetic field shows a non-monotonic behaviour,
which is rooted in the existence of magnetic impurities with a Landé g factor
different from that of the free electron. The collapse of the dephasing rate as
a function of temperature is a sign of the quenching of magnetic impurities,
which could come from Kondo coupling between magnetic impurities and
conduction electrons or Ruderman-Kittel-Kasuya-Yosida (RKKY) coupling
between magnetic impurities. The implications of our graphene experiments
are two-fold: on the one hand, they provide new knowledge about the interplay
among magnetic moments and electrons in graphene; on the other
hand, they also established an effective tool to reveal the existence of magnetic
impurities in 2d systems.
In addition to graphene, we also studied the exfoliation and stability
of thin sheets of FeSe -- a member of the Fe-based superconductors
family. Our Raman Spectroscopy, Atomic Force Microscopy, Optical Microscopy
and Time-of-Flight-Secondary-Ion-Mass-Spectroscopy experiments
show that FeSe nanosheets decay in air, precipitation of Se and oxidation
likely occurring during the decay process. Our transport measurements show that FeSe nanosheets exposed briefly to air can still retain superconductivity.
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Genre | |
Type | |
Language |
eng
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Date Available |
2018-01-15
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Provider |
Vancouver : University of British Columbia Library
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Rights |
Attribution-NonCommercial-NoDerivatives 4.0 International
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DOI |
10.14288/1.0363035
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2018-02
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Campus | |
Scholarly Level |
Graduate
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Rights URI | |
Aggregated Source Repository |
DSpace
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Rights
Attribution-NonCommercial-NoDerivatives 4.0 International