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High Pressure Studies of Quantum Materials
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| 자료유형 | 학위논문 |
|---|---|
| 서명/저자사항 | High Pressure Studies of Quantum Materials. |
| 개인저자 | Brubaker, Zachary Eric. |
| 단체저자명 | University of California, Davis. Physics. |
| 발행사항 | [S.l.]: University of California, Davis., 2019. |
| 발행사항 | Ann Arbor: ProQuest Dissertations & Theses, 2019. |
| 형태사항 | 113 p. |
| 기본자료 저록 | Dissertations Abstracts International 81-06B. Dissertation Abstract International |
| ISBN | 9781392463956 |
| 학위논문주기 | Thesis (Ph.D.)--University of California, Davis, 2019. |
| 일반주기 |
Source: Dissertations Abstracts International, Volume: 81-06, Section: B.
Advisor: Zieve, Rena. |
| 이용제한사항 | This item must not be sold to any third party vendors. |
| 요약 | The features of quantum phase transitions have been explored experimentally for nearly half a century, and general theories in the last decades have made great strides in describing the myriad features observed near such transitions: exotic superconductivity, non-Fermi liquid behavior, the emergence of heavy Fermion quasiparticles, spin resonances, etc. These features arise from various interactions, which, among other things, depend on the exact magnetic species, the crystal structure, and the degree of hybridization of valence electrons with the conduction band. High-pressure experiments allow for nearly continuous tuning of these interactions and direct measurements thereof, providing a promising environment to systematically probe their effects across wide ranges of materials. Thus, to systematically investigate the origin of exotic phases of strongly correlated materials, a series of high-pressure structural, spectroscopic, and transport measurements have been performed on d- and f-electron quantum materials.In superconducting CeRhIn_5, the Ce valence was measured by high-pressure X-ray absorption spectroscopy to probe the proposed superconducting mechanism associated with critical valence fluctuations. The obtained data do not provide evidence for this mechanism and suggest that the critical valence fluctuation scenario is unlikely in its current form.In the case of YbNiIn_4 and YbNiGa_4, high-quality crystals were grown by means of arc-melting and a series of high-pressure structural and spectroscopic probes were employed to investigate the Yb-valence. In YbNiGa_4, a smooth increase in Yb-valence is observed with increasing pressure. YbNiIn_4, on the other hand, shows evidence of an electronic topological transition near 10 GPa, which manifested itself both in spectroscopic and structural measurements. In the pressure region where YbNiIn_4 and YbNiGa_4 possess similar Yb-Yb spacings, the Yb valence reveals a precipitous drop. This drop is not captured by density functional theory calculations and implies that both the lattice degrees of freedom and the chemical environment play an important role in establishing the valence of Yb.High pressure structural and valence measurements were also performed on USb_2 to understand the origin of the AFM-FM transition near P=8 GPa. Powder X-ray diffraction measurements revealed a tetragonal-orthorhombic transition resulting in a surprisingly large 17% volume collapse as well as a transient f-occupation enhancement. Combining this with previous measurements on UP_2 and UAs_2 reveals a decreasing bulk modulus and transition pressure, and an increasing volume collapse at the structural transition with increasing atomic size in the UX_2 series.Finally, high-pressure structural, spectroscopic, and transport measurements were performed on LaCrSb_3. The ferromagnetic phase has been suppressed by P=26.5 GPa and no evidence of a structural transition has been observed up to P=55 GPa. Spectroscopic measurements revealed a gradually decreasing Cr-moment, which appears to be driving the ferromagnetic phase. Our results provide valuable feedback to DFT calculations, which predicted a suppression of the ferromagnetic phase near P=30 GPa. |
| 일반주제명 | Condensed matter physics. |
| 언어 | 영어 |
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