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| Title: | 拓樸半金屬的非線性光電流
Nonlinear Photocurrent of Topological Semimetals |
| Authors: | 許恆睿
Xu, Heng-Rui |
| Contributors: | 許琇娟
Hsu, Hsiu-Chuan
許恆睿
Xu, Heng-Rui |
| Keywords: | 外爾半金屬
體光伏效應
量子幾何張量
Weyl semimetal
Bulk photovoltaic effect
Quantum geometric tensor |
| Date: | 2024 |
| Issue Date: | 2024-08-05 15:06:43 (UTC+8) |
| Abstract: | 能帶拓樸對外爾半金屬的體光伏效應電流有相當密切的關係，像是量子幾何張量的虛部---貝里曲率和圓偏振光注入電流之間的關聯已被熟知。在線性能帶的假設下，三個循環排列的圓偏振光注入電導率加總後會正比於外爾點的手性。然而黎曼度量身為量子幾何張量的實部與傳輸特性的關係卻尚未被人清楚了解。本論文聚焦在探討二階光響應在交流電場下所產生的直流注入電流是如何被量子幾何張量的分佈影響。線偏振光引起的注入電流是由黎曼度量給出的，因此本文分析動量空間中黎曼度量的分佈，並引入改變對稱性的參數以調控電流。
本論文以四能帶的緊束縛哈密頓量為例，引入延特定方向的磁化強度破壞時間反演對稱，計算其中一節點附近的注入電導率的所有分量。除了重現圓偏振光注入電導率與結點手性的關係，另外還發現於結點附近有兩類的線偏振光電導率皆與光頻率成正比關係。並透過分析動量空間的黎曼度量分佈，發現這些電流都是因為在節點附近的量子幾何張量切片上的不對稱所得出。
在接著依序加入空間反演對稱破缺和應變項的情形下，其中三項線偏振光電導率失去正比特性，除此之外其他分量的電導率皆不受到空間反演對稱破缺和應變項的影響．
透過了解外爾半金屬的線偏振光電導率特性，其線偏振光電流效應展現出作為低頻光感器的潛力。本論文強調了能帶拓樸對光電流的影響，也提供了計算量子幾何切片來探討能帶拓樸的作用。
The bulk photovoltaic effect of Weyl semimetals is related to its band topology, such as the well-known relationship between the imaginary part of the quantum geometric tensor,
Berry curvature, and the circularly polarized light induced injection current. Under the assumption of linear bands, the sum of the circularly polarized light induced injection
conductivities in three orthogonal directions is proportional to the chirality of the Weyl point. However, the relationship between the quantum metric as the real part of the quantum geometric tensor and the transport properties is less explored. This thesis explores the relationship between the DC injection current and the quantum geometric tensor.
In addition to reproducing the relationship between the circularly polarized light injection conductivity and node chirality, the injection current induced by linearly polarized light, given by the quantum metric, is analyzed, and the distribution of the quantum metric in momentum space is examined. Parameters altering symmetry are introduced
to modulate the current. Using a four-band tight-binding Hamiltonian as an example, time-reversal symmetry is broken by introducing magnetization in a specific direction, and all components of the injection conductivity are calculated. Nonzero components of the conductivity tensor induced by linearly polarized light are identified. One class of
complements shows a positive linear relationship between conductivity and the incident light frequency, while the other class shows a negative linear relationship. By analyzing the distribution of the quantum metric in momentum space, it is found that these currents arise due to asymmetry in the quantum geometric tensor slices near the node.
Upon introducing spatial inversion symmetry breaking, three components of linear injection conductivities are no longer linearly proportional to incident light frequency. In
contrast, other components of linear injection conductivities still remain the linearity in incident light frequency.
This thesis emphasizes the impact of band topology on photocurrents and the potential of Weyl semimetals as low-frequency photodetectors. |
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| Description: | 碩士
國立政治大學
應用物理研究所
110755005 |
| Source URI: | http://thesis.lib.nccu.edu.tw/record/#G0110755005 |
| Data Type: | thesis |
| Appears in Collections: | [應用物理研究所 ] 學位論文
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