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Nonlinear Optical Responses in Type-II Weyl Semimetals
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| 자료유형 | 학위논문 |
|---|---|
| 서명/저자사항 | Nonlinear Optical Responses in Type-II Weyl Semimetals. |
| 개인저자 | Liu, Gerui. |
| 단체저자명 | University of Pennsylvania. Materials Science and Engineering. |
| 발행사항 | [S.l.]: University of Pennsylvania., 2019. |
| 발행사항 | Ann Arbor: ProQuest Dissertations & Theses, 2019. |
| 형태사항 | 137 p. |
| 기본자료 저록 | Dissertations Abstracts International 81-02B. Dissertation Abstract International |
| ISBN | 9781085568630 |
| 학위논문주기 | Thesis (Ph.D.)--University of Pennsylvania, 2019. |
| 일반주기 |
Source: Dissertations Abstracts International, Volume: 81-02, Section: B.
Advisor: Agarwal, Ritesh. |
| 이용제한사항 | This item must not be sold to any third party vendors. |
| 요약 | Weyl semimetals are gapless topological states of matter with broken inversion and/or time reversal symmetry. In this thesis, we will firstly discuss the observation of a novel photogalvanic effect in type-II Weyl semimetals including Td-MoTe2 Mo0.9W0.1Te2 and Mo0.3W0.7Te2. A circulating photocurrent is obtained under the illumination of normally incident light with circular polarization and the circulating current direction is opposite with different light helicity. Through temperature induced phase transition of MoTe2, this effect is further confirmed to exclusively occur in the Weyl phase. Since this CPGE current is controlled by the spatially varying beam profile, we define the effect as a spatially dispersive circular photogalvanic effect (sCPGE) and current amplitude is proven to be proportional to the beam gradient. By performing frequency-dependent measurements on the Weyl phase, we observe a sign reversal of sCPGE current at high energy excitation and low energy excitation. Our theoretical derivation shows that sCPGE is controlled by a unique symmetry selection rule related to asymmetric carrier excitation and relaxation, explaining the difference between Weyl phase and trivial phase as well as frequency dependent properties.Photoinduced anomalous Hall effect (AHE) is also observed in type-II Weyl semimetals. Longitudinal CPGE current is obtained under normally incident light while applying transverse bias, and the current magnitude is observed to be proportional to the bias voltage. Comparing the AHE conductivity in the 1T' phase and the Td phase of MoT2,e photoinduced AHE is found to be much more significant in Weyl phase. This effect can be understood by symmetry arguments and is described by a Fermi surface modulation under the external electric field |
| 일반주제명 | Materials science. |
| 언어 | 영어 |
| 바로가기 | 
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