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106. Programmable Interfacial Band Configuration in WS2/Bi2O2Se Heterojunctions

Author

Zhang, Hanwen, Fu, Jianhui, Carvalho, Alexandra, Poh, Eng Tuan, Chung, Jing-Yang, Feng, Minjun, Chen, Yinzhu, Wang, Bo, Shang, Qiuyu, Yang, Hengxing, Zhang, Zheng, Lim, Sharon Xiaodai, Gao, Weibo, Gradečak, Silvija, Qiu, Cheng-Wei, Lu, Junpeng, He, Chunnian, Sum, Tze Chien, and Sow, Chorng Haur

Abstract

van der Waals heterojunctions based on transition-metal dichalcogenides (TMDs) offer advanced strategies for manipulating light-emitting and light-harvesting behaviors. A crucial factor determining the light–material interaction is in the band alignment at the heterojunction interface, particularly the distinctions between type-I and type-II alignments. However, altering the band alignment from one type to another without changing the constituent materials is exceptionally difficult. Here, utilizing Bi2O2Se with a thickness-dependent band gap as a bottom layer, we present an innovative strategy for engineering interfacial band configurations in WS2/Bi2O2Se heterojunctions. In particular, we achieve tuning of the band alignment from type-I (Bi2O2Se straddling WS2) to type-II and finally to type-I (WS2straddling Bi2O2Se) by increasing the thickness of the Bi2O2Se bottom layer from monolayer to multilayer. We verified this band architecture conversion using steady-state and transient spectroscopy as well as density functional theory calculations. Using this material combination, we further design a sophisticated band architecture incorporating both type-I (WS2straddles Bi2O2Se, fluorescence-quenched) and type-I (Bi2SeO5straddles WS2, fluorescence-recovered) alignments in one sample through focused laser beam (FLB). By programming the FLB trajectory, we achieve a predesigned localized fluorescence micropattern on WS2without changing its intrinsic atomic structure. This effective band architecture design strategy represents a significant leap forward in harnessing the potential of TMD heterojunctions for multifunctional photonic applications.

Published
2024
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108. Giant Superbunching Emission from Mesoscopic Perovskite Emitter Clusters.

Author

Qiang, Gang, Cai, Hongbing, Rasmita, Abdullah, He, Ruihua, Zhou, Lei, Ru, Shihao, Cai, Xiangbin, Liu, Xiaogang, and Gao, Weibo

Subjects
PHOTON correlation, LIGHT sources, QUANTUM dots, SUPERRADIANCE, HIGH temperatures, FIELD emission
Abstract

Photon superbunching, as a crucial resource for photonic quantum technologies, is investigated in several systems. This phenomenon can be induced by both coherent collective spontaneous processes such as superfluorescence and superradiance, and cascaded emission. Although superbunching emission induced by superfluorescence and cascaded emission is demonstrated recently in perovskite quantum dot (QD) superlattice and single perovskite QD, the effect itself is not that strong, especially in the former case with a second‐order photon correlation g(2)(0) only slightly larger than 2. Here, the superbunching emission from mesoscopic CsPbBr3 emitter clusters is reported. The higher temperature and excitation power are found to suppress the superbunching effect significantly. Compared with the former results in the literature, under the same experimental conditions, that is, temperature and excitation power, much larger g(2)(0) with the maximum value of 21 being achieved at 1.6 K with an excitation power of 0.1 µW is observed. The discoveries here improve the understanding of superbunching emission in perovskite‐based materials and will enable their application in developing multi‐photon light sources for photonic quantum technologies. [ABSTRACT FROM AUTHOR]

Published
2024
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110. Interlayer donor-acceptor pair excitons in MoSe2/WSe2 moiré heterobilayer

Author

Cai, Hongbing, primary, Rasmita, Abdullah, additional, Tan, Qinghai, additional, Lai, Jia-Min, additional, He, Ruihua, additional, Cai, Xiangbin, additional, Zhao, Yan, additional, Chen, Disheng, additional, Wang, Naizhou, additional, Mu, Zhao, additional, Huang, Zumeng, additional, Zhang, Zhaowei, additional, Eng, John J. H., additional, Liu, Yuanda, additional, She, Yongzhi, additional, Pan, Nan, additional, Miao, Yansong, additional, Wang, Xiaoping, additional, Liu, Xiaogang, additional, Zhang, Jun, additional, and Gao, Weibo, additional

Published
2023
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115. Quantum-metric-induced nonlinear transport in a topological antiferromagnet

Author

Wang, Naizhou, primary, Kaplan, Daniel, additional, Zhang, Zhaowei, additional, Holder, Tobias, additional, Cao, Ning, additional, Wang, Aifeng, additional, Zhou, Xiaoyuan, additional, Zhou, Feifei, additional, Jiang, Zhengzhi, additional, Zhang, Chusheng, additional, Ru, Shihao, additional, Cai, Hongbing, additional, Watanabe, Kenji, additional, Taniguchi, Takashi, additional, Yan, Binghai, additional, and Gao, Weibo, additional

Published
2023
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117. Room-Temperature Geometrical Circular Photocurrent in Few-Layer MoS2

Author

Li, Ziqi, Liu, Jiayun, Rasmita, Abdullah, Zhang, Zhaowei, Gao, Weibo, and Chia, Elbert E. M.

Abstract

Valleytronics, i.e., the manipulation of the valley degree of freedom, offers a promising path for energy-efficient electronics. One of the key milestones in this field is the room-temperature manipulation of the valley information in thick-layered material. Using scanning photocurrent microscopy, we achieve this milestone by observing a geometrically dependent circular photocurrent in a few-layer molybdenum disulfide (MoS2) under normal incidence. Such an observation shows that the system symmetry is lower than that of bulk MoS2material, preserving the optical chirality–valley correspondence. Moreover, the circular photocurrent polarity can be reversed by applying electrical bias. We propose a model where the observed photocurrent results from the symmetry breaking and the built-in field at the electrode–sample interface. Our results show that the valley information is still retained even in thick-layered MoS2at room temperature and opens up new opportunities for exploiting the valley index through interface engineering in multilayer valleytronics devices.

Published
2024
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120. Tunable long-range spin transport in a van der Waals Fe3GeTe2/WSe2/Fe3GeTe2 spin valve.

Author

Singh, Anil Kumar, Gao, Weibo, and Deb, Pritam

Abstract

The seamless integration of two-dimensional (2D) ferromagnetic materials with similar or dissimilar materials can widen the scope of low-power spintronics. In this regard, a vertical van der Waals (vdW) heterostructure of 2D ferromagnets with semiconducting transition metal dichalcogenides (TMDCs) forms magnetic junctions with exceptional stability and electrical control. Interestingly, 2D metallic Fe3GeTe2 (FGT) reveals above room temperature Curie temperatures and has large magneto anisotropy due to spin–orbit coupling. In addition, it also possesses topological states and a large Berry curvature. Herein, we designed the FGT/WSe2/FGT vdW heterostructure with a uniform and sharp interface so that FGT could maintain its inherent electronic properties. Also, the uniform thickness of the barrier provides a smooth flow of spins through the junctions as tunneling exponentially decays with an increasing barrier thickness. However, strong energy-dependent spin polarization is crucial for achieving optimum spin valve properties, such as large tunneling magnetoresistance (TMR) along with the manipulation of the magnitude and sign reversal. We have observed a shifting of high-energy localized minority spin states toward low-energy regions, which causes spin polarization fluctuation between −42.5% and 41% over a wide range of bias voltage. This leads to a negative TMR% of ∼−100% at 0.1 V Å−1 and also a large positive TMR% at 0.2 V Å−1 and −0.4 V Å−1. Besides, the system exhibits a highly tunable large anomalous Hall conductivity (AHC) of 626 S cm−1. Interestingly, such unprecedented electronic behaviour with large and switchable spin polarization, anomalous Hall conductivity and TMR can be incorporated into MTJ devices, which provide electrical control and long-range spin transport. Additionally, the system emerges as a standout candidate in low-power spintronic devices (e.g., MRAM and magnetic sensors) owing to its distinctive energy-dependent electronic structure with a wide range of external bias. [ABSTRACT FROM AUTHOR]

Published
2024
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121. Engineering and Controlling Perovskite Emissions via Optical Quasi‐Bound‐States‐in‐the‐Continuum.

Author

Csányi, Evelin, Liu, Yan, Rezaei, Soroosh Daqiqeh, Lee, Henry Yit Loong, Tjiptoharsono, Febiana, Mahfoud, Zackaria, Gorelik, Sergey, Zhao, Xiaofei, Lim, Li Jun, Zhu, Di, Wu, Jing, Goh, Kuan Eng Johnson, Gao, Weibo, Tan, Zhi‐Kuang, Leggett, Graham, Qiu, Cheng‐Wei, and Dong, Zhaogang

Subjects
AUTOMATIC control systems, ENGINEERS, LASER pumping, ELECTRIC fields, EMISSION control, PEROVSKITE
Abstract

Metal halide perovskite quantum dots (PQDs) have emerged as promising materials due to their exceptional photoluminescence (PL) properties. A wide range of applications could benefit from adjustable luminescence properties, while preserving the physical and chemical properties of the PQDs. Therefore, post‐synthesis engineering has gained attention recently, involving the use of ion‐exchange or external stimuli, such as extreme pressure, magnetic and electric fields. Nevertheless, these methods typically suffer from spectrum broadening, intensity quenching or yield multiple bands. Alternatively, photonic antennas can modify the radiative decay channel of perovskites via the Purcell effect, with the largest wavelength shift being 8 nm to date, at an expense of fivefold intensity loss. Here, this work presents an optical nanoantenna array with polarization‐controlled quasi‐bound‐states‐in‐the‐continuum resonances, which can engineer and shift the photoluminescence wavelength over a ≈39 nm range and confers a 21‐fold emission enhancement of FAPbI3 perovskite QDs. The spectrum is engineered in a non‐invasive manner via lithographically defined antennas and the pump laser polarization at ambient conditions. This research provides a path toward advanced optoelectronic devices, such as spectrally tailored quantum emitters and lasers. [ABSTRACT FROM AUTHOR]

Published
2024
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122. Spin control in reduced-dimensional chiral perovskites

Author

Long, Guankui, Jiang, Chongyun, Sabatini, Randy, Yang, Zhenyu, Wei, Mingyang, Quan, Li Na, Liang, Qiuming, Rasmita, Abdullah, Askerka, Mikhail, Walters, Grant, Gong, Xiwen, Xing, Jun, Wen, Xinglin, Quintero-Bermudez, Rafael, Yuan, Haifeng, Xing, Guichuan, Wang, X. Renshaw, Song, Datong, Voznyy, Oleksandr, Zhang, Mingtao, Hoogland, Sjoerd, Gao, Weibo, Xiong, Qihua, and Sargent, Edward H.

Published
2018
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129. 2023 roadmap for materials for quantum technologies

Author

Becher, Christoph, Gao, Weibo, Kar, Swastik, Marciniak, Christian D., Monz, Thomas, Bartholomew, John G., Goldner, Philippe, Loh, Huanqian, Marcellina, Elizabeth, Goh, Kuan Eng Johnson, Koh, Teck Seng, Weber, Bent, Mu, Zhao, Tsai, Jeng Yuan, Yan, Qimin, Huber-Loyola, Tobias, Höfling, Sven, Gyger, Samuel, Steinhauer, Stephan, Zwiller, Val, Becher, Christoph, Gao, Weibo, Kar, Swastik, Marciniak, Christian D., Monz, Thomas, Bartholomew, John G., Goldner, Philippe, Loh, Huanqian, Marcellina, Elizabeth, Goh, Kuan Eng Johnson, Koh, Teck Seng, Weber, Bent, Mu, Zhao, Tsai, Jeng Yuan, Yan, Qimin, Huber-Loyola, Tobias, Höfling, Sven, Gyger, Samuel, Steinhauer, Stephan, and Zwiller, Val

Abstract

Quantum technologies are poised to move the foundational principles of quantum physics to the forefront of applications. This roadmap identifies some of the key challenges and provides insights on material innovations underlying a range of exciting quantum technology frontiers. Over the past decades, hardware platforms enabling different quantum technologies have reached varying levels of maturity. This has allowed for first proof-of-principle demonstrations of quantum supremacy, for example quantum computers surpassing their classical counterparts, quantum communication with reliable security guaranteed by laws of quantum mechanics, and quantum sensors uniting the advantages of high sensitivity, high spatial resolution, and small footprints. In all cases, however, advancing these technologies to the next level of applications in relevant environments requires further development and innovations in the underlying materials. From a wealth of hardware platforms, we select representative and promising material systems in currently investigated quantum technologies. These include both the inherent quantum bit systems and materials playing supportive or enabling roles, and cover trapped ions, neutral atom arrays, rare earth ion systems, donors in silicon, color centers and defects in wide-band gap materials, two-dimensional materials and superconducting materials for single-photon detectors. Advancing these materials frontiers will require innovations from a diverse community of scientific expertise, and hence this roadmap will be of interest to a broad spectrum of disciplines., QC 20230704

Published
2023
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130. Van der Waals engineering for quantum-entangled photon generation

Author

Kallioniemi, Leevi, Lyu, Xiaodan, He, Ruihua, Rasmita, Abdullah, Duan, Ruihuan, Liu, Zheng, and Gao, Weibo

Abstract

Van der Waals engineering serves as a powerful tool to tailor material properties and design excitonic devices. Here we report quantum-entangled photon pair generation through van der Waals engineering with two-dimensional materials. We align two van der Waals thin layers perpendicular to each other, yielding polarization-entangled photon pairs through the interference of biphoton emission in the two flakes. The polarization-entangled state is measured with a fidelity up to 86 ± 0.7%. The compatibility of van der Waals engineering with on-chip photonics opens new possibilities for entangled photon source integration at the subwavelength scale.

Published
2024
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131. Charge-depletion-enhanced WSe2quantum emitters on gold nanogap arrays with near-unity quantum efficiency

Author

Cai, Hongbing, Rasmita, Abdullah, He, Ruihua, Zhang, Zhaowei, Tan, Qinghai, Chen, Disheng, Wang, Naizhou, Mu, Zhao, Eng, John J. H., She, Yongzhi, Pan, Nan, Wang, Qian, Dong, Zhaogang, Wang, Xiaoping, Wang, Juan, Miao, Yansong, Singh, Ranjan, Qiu, Cheng-Wei, Liu, Xiaogang, and Gao, Weibo

Abstract

Achieving unity quantum efficiency in single-photon emitters (SPEs) is a holy grail in quantum information science. Through plasmonic coupling it is possible to increase the quantum efficiency of SPEs by increasing the radiative decay rate, but to approach unity quantum efficiency, non-radiative decay must be mitigated. Here we show that non-radiative decay in two-dimensional WSe2quantum emitters can be electrically suppressed through charge depletion by using dual gate configurations under a large electric field. In this condition, for site-controlled SPEs in WSe2coupled to gold nanogaps, the SPE transition quantum efficiency after gating is increased to 76.4 ± 14.6% on average, with some SPEs reaching near-unity (more than 90%) quantum efficiency. This study provides a new approach for tuning SPEs with an applied gate voltage and motivates further theoretical and experimental studies of SPE enhancement on vertically aligned nanogaps.

Published
2024
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133. 2023 roadmap for materials for quantum technologies

Author

Becher, Christoph, primary, Gao, Weibo, additional, Kar, Swastik, additional, Marciniak, Christian D, additional, Monz, Thomas, additional, Bartholomew, John G, additional, Goldner, Philippe, additional, Loh, Huanqian, additional, Marcellina, Elizabeth, additional, Goh, Kuan Eng Johnson, additional, Koh, Teck Seng, additional, Weber, Bent, additional, Mu, Zhao, additional, Tsai, Jeng-Yuan, additional, Yan, Qimin, additional, Huber-Loyola, Tobias, additional, Höfling, Sven, additional, Gyger, Samuel, additional, Steinhauer, Stephan, additional, and Zwiller, Val, additional

Published
2023
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