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215 results on '"Wu, Weixiong"'

13. Distinct quantum anomalous Hall ground states induced by magnetic disorders

Author

Liu, Chang, Ou, Yunbo, Feng, Yang, Jiang, Gaoyuan, Wu, Weixiong, Li, Shaorui, Cheng, Zijia, He, Ke, Ma, Xucun, Xue, Qikun, and Wang, Yayu

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

The quantum anomalous Hall (QAH) effect in magnetic topological insulator (TI) represents a new state of matter originated from the interplay between topology and magnetism. The defining characteristics of the QAH ground state are the quantized Hall resistivity ($\rho_{yx}$) and vanishing longitudinal resistivity ($\rho_{xx}$) in the absence of external magnetic field. A fundamental question concerning the QAH effect is whether it is merely a zero-magnetic-field quantum Hall (QH) effect, or if it can host unique quantum phases and phase transitions that are unavailable elsewhere. The most dramatic departure of the QAH systems from other QH systems lies in the strong magnetic disorders that induce spatially random magnetization. Because disorder and magnetism play pivotal roles in the phase diagram of two-dimensional electron systems, the high degree of magnetic disorders in QAH systems may create novel phases and quantum critical phenomena. In this work, we perform systematic transport studies of a series of magnetic TIs with varied strength of magnetic disorders. We find that the ground state of QAH effect can be categorized into two distinct classes: the QAH insulator and anomalous Hall (AH) insulator phases, as the zero-magnetic-field counterparts of the QH liquid and Hall insulator in the QH systems. In the low disorder limit of the QAH insulator regime, we observe a universal quantized longitudinal resistance $\rho_{xx} = h/e^{2}$ at the coercive field. In the AH insulator regime, we find that a magnetic field can drive it to the QAH insulator phase through a quantum critical point with distinct scaling behaviors from that in the QH phase transition. We propose that the transmission between chiral edge states at domain boundaries, tunable by disorder and magnetic fields, is the key for determining the QAH ground state., Comment: 17 pages, 5 figures

Published
2021
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21. Quantum anomalous Hall multilayers grown by molecular beam epitaxy

Author

Jiang, Gaoyuan, Feng, Yang, Wu, Weixiong, Li, Shaorui, Bai, Yunhe, Li, Yaoxin, Zhang, Qinghua, Gu, Lin, Feng, Xiao, Zhang, Ding, Song, Canli, Wang, Lili, Li, Wei, Ma, Xu-Cun, Xue, Qi-Kun, Wang, Yayu, and He, Ke

Subjects
Condensed Matter - Materials Science
Abstract

Quantum anomalous Hall (QAH) effect is a quantum Hall effect that occurs without the need of external magnetic field. A system composed of multiple parallel QAH layers is an effective high Chern number QAH insulator and the key to the applications of the dissipationless chiral edge channels in low energy consumption electronics. Such a QAH multilayer can also be engineered into other exotic topological phases such as a magnetic Weyl semimetal with only one pair of Weyl points. This work reports the first experimental realization of QAH multilayers in the superlattices composed of magnetically doped (Bi,Sb)$_2$Te$_3$ topological insulator and CdSe normal insulator layers grown by molecular beam epitaxy. The obtained multilayer samples show quantized Hall resistance $h/Ne$$^2$, where $h$ is the Planck's constant, $e$ is the elementary charge and $N$ is the number of the magnetic topological insulator layers, resembling a high Chern number QAH insulator., Comment: 9 pages, 3 figures

Published
2018
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35. Corrigendum to [Energy, 300 (2024)131560]

Author

Li, Kuijie, Gao, Xinlei, Peng, Shijian, Wang, Shengshi, Zhang, Weixin, Liu, Peng, Wu, Weixiong, Wang, Huizhi, Wang, Yu, Feng, Xuning, Cao, Yuan-cheng, Wen, Jinyu, Cheng, Shijie, and Ouyang, Minggao

Published
2024
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39. A Path-Based Switch Open Circuit Fault-Tolerant Method for Three-Phase DAB Converter

Author

Guan, Yuanpeng, Xiao, Yiting, Qin, Li, Liu, Xiong, Deng, Hui, and Wu, Weixiong

Abstract

The three-phase dual active bridge (DAB3) converter achieves the bidirectional power transmission and voltage conversion in dc power grid. However, DAB3 is susceptible to switch open circuit fault (SOCF), causing transmission power loss and excessive current stress. Thus, a path-based fault-tolerant method (PFTM) for SOCF in DAB3 is proposed. First, the transferred energy of each phase is investigated by modality analysis of DAB3, thus, a path energization method is proposed for PFTM, and switching pattern reconfiguration strategy is summarized by switching functions during SOCF, enlarging maximum transmission power within maximum high-frequency-link (HFL) inductor current. Moreover, in the PFTM, the fault paths/legs are employed, reconfiguring the current path of modality, actively adjusting the on-time of antiparallel diode, and realizing the bidirectional transmission power improvement. Furthermore, the optimization strategy of phase shift ratio is proposed to reduce HFL current stress and keep zero-voltage switching, when SOCF is in primary and secondary sides. Compared with traditional methods, the PFTM can realize a wider power range and voltage gain, and a higher maximum transmission power, to ensure the safety and reliability of DAB3. Finally, experimental results verify the theoretical analysis.

Published
2024
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41. Understanding the influence of secondary building units on the thermal conductivity of metal–organic frameworks via high-throughput computational screening.

Author

Lin, Yuanchuang, Cheng, Ruihuan, Liang, Tiangui, Wu, Weixiong, Li, Song, and Li, Wei

Abstract

The thermal conductivity of metal–organic frameworks (MOFs) has garnered increasing interest due to their potential applications in energy-related fields. However, due to the diversity of building units, understanding the relationship between MOF structures and their thermal conductivity remains an imperative challenge. In this study, we predicted the thermal conductivity (κ) of MOFs using equilibrium molecular dynamics (EMD) simulations and investigated the contribution of structure properties to their thermal conductivity. It is revealed that the arrangement of secondary building units (SBUs) with a closer distance of metal atoms, a larger proportion of metal elements, and transition metal elements (Fe, Mn, and Co) leads to high thermal conductivity. To generally quantify the influence of such factors on thermal conductivity, the pathway factors with SBU influence (Pm) were proposed and can be used to efficiently classify structures into high, medium, and low thermal conductivity types. It was found that Pm indicates that MOFs with met topology tend to have high thermal conductivity, while rna and pcu topologies naturally tend to possess medium and low thermal conductivity. Moreover, it was also suggested that taking Pm as a descriptor in the machine learning algorithms can significantly improve the prediction accuracy for thermal conductivity. This study offers molecular insight into the impact of various SBUs on thermal conductivity in framework-based nanomaterials, which may guide the rational design of nanoporous materials with desirable thermal conductivity. [ABSTRACT FROM AUTHOR]

Published
2023
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42. Evaluating the Influence of Land Use and Landscape Pattern on the Spatial Pattern of Water Quality in the Pearl River Basin.

Author

Liang, Xuewen, Pan, Yue, Li, Cunwu, Wu, Weixiong, and Huang, Xusheng

Abstract

Differences in land use and landscape patterns have become crucial factors affecting regional water quality. In order to investigate the effects of different land use and landscape patterns on water quality, this study used dissolved oxygen (DO), ammonia nitrogen (NH4+-N), and potassium permanganate index (CODMn) from 147 conventional water quality monitoring stations in the Pearl River basin of China from January to December 2021 as representative water quality parameters. The quantitative relationship between land use, landscape pattern, and water quality in the Pearl River basin was investigated using geographic information system technology (GIS) and partial least squares (PLS). The results showed that the overall water quality of the Pearl River basin was relatively positive and mainly threatened by organic pollution. The water quality of the Pearl River basin was affected by the spatial characteristics of land use and landscape pattern, showing a poorer spatial pattern on the eastern and western ends and a better one in the central part of the basin. The developed PLS regression model could better explain the quantitative relationship between water quality, land use, and landscape pattern, concluding that unused urban land has the greatest impact on water quality, with an impact coefficient of more than 0.10. The interspersion juxtaposition index (IJI) for representing landscape patterns had the greatest impact on water quality indicators, with an impact coefficient of −0.15 on DO, 0.13 on NH4+-N, and 0.15 on CODMn, respectively. Meanwhile, land use types such as unused land and water and landscape patterns indicated by the Shannon diversity index (SHDI) and the contagion index (CONTAG) had significant effects on watershed water quality. The results of the study provide a reference value for the optimal adjustment of land use structure and water quality improvement in the basin. [ABSTRACT FROM AUTHOR]

Published
2023
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