This title appears in the Scientific Report :
2021
Please use the identifier:
http://hdl.handle.net/2128/28016 in citations.
Single crystal growth and neutron scattering studies of novel quantum materials
Single crystal growth and neutron scattering studies of novel quantum materials
The recent development of theoretical and experimental study of emergent phenomena, such as anomalous Hall effects, topological electronic band structures as well as quantum spin liquid states in condensed matter physics have evoked tremendous research interest in the search and study of novel quant...
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Personal Name(s): | Wang, Xiao (Corresponding author) |
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Contributing Institute: |
Heinz Maier-Leibnitz Zentrum; MLZ Streumethoden; JCNS-2 JCNS-FRM-II; JCNS-FRM-II JCNS-4; JCNS-4 |
Imprint: |
Jülich
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
2021
|
Physical Description: |
VI, 145 S. |
Dissertation Note: |
Dissertation, RWTH Aachen, 2021 |
ISBN: |
978-3-95806-546-8 |
Document Type: |
Book Dissertation / PhD Thesis |
Research Program: |
Materials – Quantum, Complex and Functional Materials Jülich Centre for Neutron Research (JCNS) (FZJ) |
Series Title: |
Schriften des Forschungszentrums Jülich. Reihe Schlüsseltechnologien / Key Technologies
239 |
Subject (ZB): | |
Link: |
OpenAccess |
Publikationsportal JuSER |
The recent development of theoretical and experimental study of emergent phenomena, such as anomalous Hall effects, topological electronic band structures as well as quantum spin liquid states in condensed matter physics have evoked tremendous research interest in the search and study of novel quantum materials. High quality single crystal samples of the quantum materials, which serve as a key prerequisite to study the novel properties are of great importance in the study of quantum materials. In this PhD work, employing two cutting-edge methods: molten flux and chemical vapour transport, series of novel quantum material single high quality crystal samples have been grown, such as CeSb, PrSb, NdSb, $\alpha$-RuCl$_{3}$, Mn$_{3}$Sn,Sr$_{2}$IrO$_{4}$, Cr$_{2}$Ge$_{2}$Te$_{6}$, Cr$_{2}$Si$_{2}$Te$_{6}$, CeZn$_{3}$As$_{3}$, PrZn$_{3}$As$_{3}$, PtBi$_{2}$, ZrTe$_{5}$, which have been studied intensively in this PhD work as well as other cooperators. The second important part of this PhD thesis is to study the correlation among crystal structure, magnetic structure and physical properties in two novel quantum materials: Mn$_{3}$Sn and $\alpha$-RuCl$_{3}$ by comprehensive characterization methods. Mn$_{3}$Sn, which is proposed to be a candidate of magnetic Weyl semimetal has been studied by a combination of polarised and unpolarised neutron diffraction techniques in this work. Single crystals of topological semimetal Mn$_{3}$Sn have been grown by Sn self-flux method. The magnetic susceptibility and electronic resistivity showed a magnetic phase transition at 285K and below that, the anomalous Hall effects at room temperature disappeared completely. With a combination of unpolarised and polarised neutron study, the crystal structure and magnetic structure at low temperature have been determined and a novel double-q magnetic ground state is found. As a result of breaking symmetry, AHE could not be realised in this kind of magnetic structure but the double-q magnetic structure has offered a rare case to study the non coplanar order in materials with kagomé lattice.a-RuCl3, which is a candidate to realise Kitaev quantum spin liquid, is a layered two dimensional materials bonded with the weak Van der Weals force. Growing high quality samples of a-RuCl$_{3}$ single crystals has been a big challenge since the stacking faults will be introduced inevitably. In this thesis, single crystals up to 700 mg were successfully grown by optimising the crystal growth conditions. Based on the high quality single crystals, the low temperature crystal structure of a-RuCl$_{3}$ has been proved to be R$\overline{3}$ instead of C2/$\textit{m}$ by single crystal neutron diffraction which demonstrates that a-RuCl$_{3}$ maybe a perfect candidate to study Kitaev physics without lattice distortion. Besides, with spherical polarised neutron analysis the ordered magnetic moment direction of Ru3$^{+}$ has been precisely determined which will help to reveal the microscopic interaction in Kitaev quantum spin liquids physics. In addition, the phase diagram of a-RuCl$_{3}$ under isostatic pressures has also been determined by single crystal neutron diffraction. The results reveal the magnetic order in a-RuCl$_{3}$ could be effectively suppressed with increase of external hydrostatic pressure. However, a pressure induced structural phase transition occurs when the pressure is higher than 0.15 GPa. Despite that the quantum spin liquid state is not realised in a-RuCl$_{3}$ by the isostatic pressure, this result has proved that the pressure could change the transition temperature in Kitaev materials explicitly and will shed lights on the pressure tuning magnetic order in similar materials. |