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111 results on '"Xu, Xiaodong"'

2. Evolution of the Valley Position in Bulk Transition-Metal Chalcogenides and Their Monolayer Limit

Author

Yuan, Hongtao, Liu, Zhongkai, Xu, Gang, Zhou, Bo, Wu, Sanfeng, Dumcenco, Dumitru, Yan, Kai, Zhang, Yi, Mo, Sung-Kwan, Dudin, Pavel, Kandyba, Victor, Yablonskikh, Mikhail, Barinov, Alexei, Shen, Zhixun, Zhang, Shoucheng, Huang, Yingsheng, Xu, Xiaodong, Hussain, Zahid, Hwang, Harold Y, Cui, Yi, and Chen, Yulin

Subjects
Quantum Physics, Physical Sciences, Condensed Matter Physics, angle-resolved photoemission spectroscopy, band structure, transition metal dichalcogenides, valleytronics, Nanoscience & Nanotechnology
Abstract

Layered transition metal chalcogenides with large spin orbit coupling have recently sparked much interest due to their potential applications for electronic, optoelectronic, spintronics, and valleytronics. However, most current understanding of the electronic structure near band valleys in momentum space is based on either theoretical investigations or optical measurements, leaving the detailed band structure elusive. For example, the exact position of the conduction band valley of bulk MoS2 remains controversial. Here, using angle-resolved photoemission spectroscopy with submicron spatial resolution (micro-ARPES), we systematically imaged the conduction/valence band structure evolution across representative chalcogenides MoS2, WS2, and WSe2, as well as the thickness dependent electronic structure from bulk to the monolayer limit. These results establish a solid basis to understand the underlying valley physics of these materials, and also provide a link between chalcogenide electronic band structure and their physical properties for potential valleytronics applications.

Published
2016

5. Quenched Excitons in WSe2/α-RuCl3 Heterostructures Revealed by Multimessenger Nanoscopy

Author

Sternbach, Aaron J., primary, Vitalone, Rocco A., additional, Shabani, Sara, additional, Zhang, Jin, additional, Darlington, Thomas P., additional, Moore, Samuel L., additional, Chae, Sang Hoon, additional, Seewald, Eric, additional, Xu, Xiaodong, additional, Dean, Cory R., additional, Zhu, Xiaoyang, additional, Rubio, Angel, additional, Hone, James, additional, Pasupathy, Abhay N., additional, Schuck, P. James, additional, and Basov, D. N., additional

Published
2023
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8. Gate-Tunable Proximity Effects in Graphene on Layered Magnetic Insulators

Author

Tseng, Chun-Chih, primary, Song, Tiancheng, additional, Jiang, Qianni, additional, Lin, Zhong, additional, Wang, Chong, additional, Suh, Jaehyun, additional, Watanabe, Kenji, additional, Taniguchi, Takashi, additional, McGuire, Michael A., additional, Xiao, Di, additional, Chu, Jiun-Haw, additional, Cobden, David H., additional, Xu, Xiaodong, additional, and Yankowitz, Matthew, additional

Published
2022
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9. Quenched Excitons in WSe2/α-RuCl3Heterostructures Revealed by Multimessenger Nanoscopy

Author

Sternbach, Aaron J., Vitalone, Rocco A., Shabani, Sara, Zhang, Jin, Darlington, Thomas P., Moore, Samuel L., Chae, Sang Hoon, Seewald, Eric, Xu, Xiaodong, Dean, Cory R., Zhu, Xiaoyang, Rubio, Angel, Hone, James, Pasupathy, Abhay N., Schuck, P. James, and Basov, D. N.

Abstract

We investigate heterostructures composed of monolayer WSe2stacked on α-RuCl3using a combination of Terahertz (THz) and infrared (IR) nanospectroscopy and imaging, scanning tunneling spectroscopy (STS), and photoluminescence (PL). Our observations reveal itinerant carriers in the heterostructure prompted by charge transfer across the WSe2/α-RuCl3interface. Local STS measurements show the Fermi level is shifted to the valence band edge of WSe2which is consistent with p-type doping and verified by density functional theory (DFT) calculations. We observe prominent resonances in near-IR nano-optical and PL spectra, which are associated with the A-exciton of WSe2. We identify a concomitant, near total, quenching of the A-exciton resonance in the WSe2/α-RuCl3heterostructure. Our nano-optical measurements show that the charge-transfer doping vanishes while excitonic resonances exhibit near-total recovery in “nanobubbles”, where WSe2and α-RuCl3are separated by nanometer distances. Our broadband nanoinfrared inquiry elucidates local electrodynamics of excitons and an electron–hole plasma in the WSe2/α-RuCl3system.

Published
2023
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16. Magnetic Order and Symmetry in the 2D Semiconductor CrSBr

Author

Lee, Kihong, primary, Dismukes, Avalon H., additional, Telford, Evan J., additional, Wiscons, Ren A., additional, Wang, Jue, additional, Xu, Xiaodong, additional, Nuckolls, Colin, additional, Dean, Cory R., additional, Roy, Xavier, additional, and Zhu, Xiaoyang, additional

Published
2021
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18. Intertwined Topological and Magnetic Orders in Atomically Thin Chern Insulator MnBi2Te4

Author

Ovchinnikov, Dmitry, primary, Huang, Xiong, additional, Lin, Zhong, additional, Fei, Zaiyao, additional, Cai, Jiaqi, additional, Song, Tiancheng, additional, He, Minhao, additional, Jiang, Qianni, additional, Wang, Chong, additional, Li, Hao, additional, Wang, Yayu, additional, Wu, Yang, additional, Xiao, Di, additional, Chu, Jiun-Haw, additional, Yan, Jiaqiang, additional, Chang, Cui-Zu, additional, Cui, Yong-Tao, additional, and Xu, Xiaodong, additional

Published
2021
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20. Metasurface Integrated Monolayer Exciton Polariton

Author

Chen, Yueyang, primary, Miao, Shengnan, additional, Wang, Tianmeng, additional, Zhong, Ding, additional, Saxena, Abhi, additional, Chow, Colin, additional, Whitehead, James, additional, Gerace, Dario, additional, Xu, Xiaodong, additional, Shi, Su-Fei, additional, and Majumdar, Arka, additional

Published
2020
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21. Monolayer Semiconductor Auger Detector

Author

Chow, Colin Ming Earn, primary, Yu, Hongyi, additional, Schaibley, John R., additional, Rivera, Pasqual, additional, Finney, Joseph, additional, Yan, Jiaqiang, additional, Mandrus, David, additional, Taniguchi, Takashi, additional, Watanabe, Kenji, additional, Yao, Wang, additional, Cobden, David Henry, additional, and Xu, Xiaodong, additional

Published
2020
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22. Two-Dimensional van der Waals Nanoplatelets with Robust Ferromagnetism

Author

De Siena, Michael C., primary, Creutz, Sidney E., additional, Regan, Annie, additional, Malinowski, Paul, additional, Jiang, Qianni, additional, Kluherz, Kyle T., additional, Zhu, Guomin, additional, Lin, Zhong, additional, De Yoreo, James J., additional, Xu, Xiaodong, additional, Chu, Jiun-Haw, additional, and Gamelin, Daniel R., additional

Published
2020
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23. Many-Body Exciton and Intervalley Correlations in Heavily Electron-Doped WSe2Monolayers

Author

Li, Jing, Goryca, Mateusz, Choi, Junho, Xu, Xiaodong, and Crooker, Scott A.

Abstract

In monolayer transition-metal dichalcogenide semiconductors, many-body correlations can manifest in optical spectra when electron–hole pairs (excitons) are photoexcited into a 2D Fermi sea of mobile carriers. At low carrier densities, the formation of charged excitons (X±) is well documented. However, in WSe2monolayers, an additional absorption resonance, often called X–′, emerges at high electron density. Its origin is not understood. Here, we investigate the X–′ state via polarized absorption spectroscopy of gated WSe2monolayers in magnetic fields to 60T. Field-induced filling and emptying of the lowest optically active Landau level in the K′ valley causes repeated quenching of the corresponding optical absorption. Surprisingly, these quenchings are accompanied by absorption changes to higher Landau levels in both K′ and Kvalleys, which are unoccupied. These results cannot be reconciled within a single-particle picture, and demonstrate the many-body nature and intervalley correlations of the X–′ quasiparticle state.

Published
2022
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24. Atomically Thin CrCl3: An In-Plane Layered Antiferromagnetic Insulator

Author

Cai, Xinghan, primary, Song, Tiancheng, additional, Wilson, Nathan P., additional, Clark, Genevieve, additional, He, Minhao, additional, Zhang, Xiaoou, additional, Taniguchi, Takashi, additional, Watanabe, Kenji, additional, Yao, Wang, additional, Xiao, Di, additional, McGuire, Michael A., additional, Cobden, David H., additional, and Xu, Xiaodong, additional

Published
2019
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25. Voltage Control of a van der Waals Spin-Filter Magnetic Tunnel Junction

Author

Song, Tiancheng, primary, Tu, Matisse Wei-Yuan, additional, Carnahan, Caitlin, additional, Cai, Xinghan, additional, Taniguchi, Takashi, additional, Watanabe, Kenji, additional, McGuire, Michael A., additional, Cobden, David H., additional, Xiao, Di, additional, Yao, Wang, additional, and Xu, Xiaodong, additional

Published
2019
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27. Ultrathin van der Waals Metalenses

Author

Liu, Chang-Hua, primary, Zheng, Jiajiu, additional, Colburn, Shane, additional, Fryett, Taylor K., additional, Chen, Yueyang, additional, Xu, Xiaodong, additional, and Majumdar, Arka, additional

Published
2018
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28. Even–Odd Layer-Dependent Anomalous Hall Effect in Topological Magnet MnBi2Te4Thin Films

Author

Zhao, Yi-Fan, Zhou, Ling-Jie, Wang, Fei, Wang, Guang, Song, Tiancheng, Ovchinnikov, Dmitry, Yi, Hemian, Mei, Ruobing, Wang, Ke, Chan, Moses H. W., Liu, Chao-Xing, Xu, Xiaodong, and Chang, Cui-Zu

Abstract

Recently, MnBi2Te4has been demonstrated to be an intrinsic magnetic topological insulator and the quantum anomalous Hall (QAH) effect was observed in exfoliated MnBi2Te4flakes. Here, we used molecular beam epitaxy (MBE) to grow MnBi2Te4films with thickness down to 1 septuple layer (SL) and performed thickness-dependent transport measurements. We observed a nonsquare hysteresis loop in the antiferromagnetic state for films with thickness greater than 2 SL. The hysteresis loop can be separated into two AH components. We demonstrated that one AH component with the larger coercive field is from the dominant MnBi2Te4phase, whereas the other AH component with the smaller coercive field is from the minor Mn-doped Bi2Te3phase. The extracted AH component of the MnBi2Te4phase shows a clear even–odd layer-dependent behavior. Our studies reveal insights on how to optimize the MBE growth conditions to improve the quality of MnBi2Te4films.

Published
2021
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30. Quantum-Enhanced Tunable Second-Order Optical Nonlinearity in Bilayer Graphene

Author

Wu, Sanfeng, Mao, Li, Jones, Aaron M., Yao, Wang, Zhang, Chuanwei, and Xu, Xiaodong

Abstract

Second order optical nonlinear processes involve the coherent mixing of two electromagnetic waves to generate a new optical frequency, which plays a central role in a variety of applications, such as ultrafast laser systems, rectifiers, modulators, and optical imaging. However, progress is limited in the mid-infrared (MIR) region due to the lack of suitable nonlinear materials. It is desirable to develop a robust system with a strong, electrically tunable second order optical nonlinearity. Here, we demonstrate theoretically that AB-stacked bilayer graphene (BLG) can exhibit a giant and tunable second order nonlinear susceptibility χ(2)once an in-plane electric field is applied. χ(2)can be electrically tuned from 0 to ∼105pm/V, 3 orders of magnitude larger than the widely used nonlinear crystal AgGaSe2. We show that the unusually large χ(2)arise from two different quantum enhanced two-photon processes thanks to the unique electronic spectrum of BLG. The tunable electronic bandgap of BLG adds additional tunability on the resonance of χ(2), which corresponds to a tunable wavelength ranging from ∼2.6 to ∼3.1 μm for the up-converted photon. Combined with the high electron mobility and optical transparency of the atomically thin BLG, our scheme suggests a new regime of nonlinear photonics based on BLG.

Published
2024
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32. Dynamic Optical Tuning of Interlayer Interactions in the Transition Metal Dichalcogenides

Author

Mannebach, Ehren M., primary, Nyby, Clara, additional, Ernst, Friederike, additional, Zhou, Yao, additional, Tolsma, John, additional, Li, Yao, additional, Sher, Meng-Ju, additional, Tung, I-Cheng, additional, Zhou, Hua, additional, Zhang, Qi, additional, Seyler, Kyle L., additional, Clark, Genevieve, additional, Lin, Yu, additional, Zhu, Diling, additional, Glownia, James M., additional, Kozina, Michael E., additional, Song, Sanghoon, additional, Nelson, Silke, additional, Mehta, Apurva, additional, Yu, Yifei, additional, Pant, Anupum, additional, Aslan, Burak, additional, Raja, Archana, additional, Guo, Yinsheng, additional, DiChiara, Anthony, additional, Mao, Wendy, additional, Cao, Linyou, additional, Tongay, Sefaattin, additional, Sun, Jifeng, additional, Singh, David J., additional, Heinz, Tony F., additional, Xu, Xiaodong, additional, MacDonald, Allan H., additional, Reed, Evan, additional, Wen, Haidan, additional, and Lindenberg, Aaron M., additional

Published
2017
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33. Nanocavity Clock Spectroscopy: Resolving Competing Exciton Dynamics in WSe2/MoSe2Heterobilayers

Author

May, Molly A., Jiang, Tao, Du, Chenfeng, Park, Kyoung-Duck, Xu, Xiaodong, Belyanin, Alexey, and Raschke, Markus B.

Abstract

Transition-metal dichalcogenide heterostructures are an emergent platform for novel many-body states from exciton condensates to nanolasers. However, their exciton dynamics are difficult to disentangle due to multiple competing processes with time scales varying over many orders of magnitude. Using a configurable nano-optical cavity based on a plasmonic scanning probe tip, the radiative (rad) and nonradiative (nrad) relaxation of intra- and interlayer excitons is controlled. Tuning their relative rates in a WSe2/MoSe2heterobilayer over 6 orders of magnitude in tip-enhanced photoluminescence spectroscopy reveals a cavity-induced crossover from nonradiative quenching to Purcell-enhanced radiation. Rate equation modeling with the interlayer charge transfer time as a reference clock allows for a comprehensive determination from the long interlayer exciton (IX) radiative lifetime τIXrad= (94 ± 27) ns to the 5 orders of magnitude faster competing nonradiative lifetime τIXnrad= (0.6 ± 0.2) ps. This approach of nanocavity clock spectroscopy is generally applicable to a wide range of excitonic systems with competing decay pathways.

Published
2021
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35. Interlayer Exciton Optoelectronics in a 2D Heterostructure p–n Junction

Author

Ross, Jason S., primary, Rivera, Pasqual, additional, Schaibley, John, additional, Lee-Wong, Eric, additional, Yu, Hongyi, additional, Taniguchi, Takashi, additional, Watanabe, Kenji, additional, Yan, Jiaqiang, additional, Mandrus, David, additional, Cobden, David, additional, Yao, Wang, additional, and Xu, Xiaodong, additional

Published
2017
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46. Spindle-like Mesoporous α‑Fe2O3 Anode Material Prepared from MOF Template for High-Rate Lithium Batteries.

Author

Xu, Xiaodong, Cao, Ruiguo, Jeong, Sookyung, and Cho, Jaephil

Subjects
*ANODES, *METAL-organic frameworks, *LITHIUM cells
Abstract

Spindle-like porous α-Fe2O3 was prepared from an iron-based metal organic framework (MOF) template. When tested as anode material for lithium batteries (LBs), this spindle-like porous α-Fe2O3 shows greatly enhanced performance of Li storage. The particle with a length and width of ∼0.8 and ∼0.4 μm, respectively, was composed of clustered Fe2O3 nanoparticles with sizes of <20 nm. The capacity of the porous α-Fe2O3 retained 911 mAh g–1 after 50 cycles at a rate of 0.2 C. Even when cycled at 10 C, comparable capacity of 424 mAh g–1 could be achieved. [ABSTRACT FROM AUTHOR]

Published
2012
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47. Quenched Excitons in WSe 2 /α-RuCl 3 Heterostructures Revealed by Multimessenger Nanoscopy.

Author

Sternbach AJ, Vitalone RA, Shabani S, Zhang J, Darlington TP, Moore SL, Chae SH, Seewald E, Xu X, Dean CR, Zhu X, Rubio A, Hone J, Pasupathy AN, Schuck PJ, and Basov DN

Abstract

We investigate heterostructures composed of monolayer WSe 2 stacked on α-RuCl 3 using a combination of Terahertz (THz) and infrared (IR) nanospectroscopy and imaging, scanning tunneling spectroscopy (STS), and photoluminescence (PL). Our observations reveal itinerant carriers in the heterostructure prompted by charge transfer across the WSe 2 /α-RuCl 3 interface. Local STS measurements show the Fermi level is shifted to the valence band edge of WSe 2 which is consistent with p-type doping and verified by density functional theory (DFT) calculations. We observe prominent resonances in near-IR nano-optical and PL spectra, which are associated with the A-exciton of WSe 2 . We identify a concomitant, near total, quenching of the A-exciton resonance in the WSe 2 /α-RuCl 3 heterostructure. Our nano-optical measurements show that the charge-transfer doping vanishes while excitonic resonances exhibit near-total recovery in "nanobubbles", where WSe 2 and α-RuCl 3 are separated by nanometer distances. Our broadband nanoinfrared inquiry elucidates local electrodynamics of excitons and an electron-hole plasma in the WSe 2 /α-RuCl 3 system.

Published
2023
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48. Even-Odd Layer-Dependent Anomalous Hall Effect in Topological Magnet MnBi 2 Te 4 Thin Films.

Author

Zhao YF, Zhou LJ, Wang F, Wang G, Song T, Ovchinnikov D, Yi H, Mei R, Wang K, Chan MHW, Liu CX, Xu X, and Chang CZ

Abstract

Recently, MnBi 2 Te 4 has been demonstrated to be an intrinsic magnetic topological insulator and the quantum anomalous Hall (QAH) effect was observed in exfoliated MnBi 2 Te 4 flakes. Here, we used molecular beam epitaxy (MBE) to grow MnBi 2 Te 4 films with thickness down to 1 septuple layer (SL) and performed thickness-dependent transport measurements. We observed a nonsquare hysteresis loop in the antiferromagnetic state for films with thickness greater than 2 SL. The hysteresis loop can be separated into two AH components. We demonstrated that one AH component with the larger coercive field is from the dominant MnBi 2 Te 4 phase, whereas the other AH component with the smaller coercive field is from the minor Mn-doped Bi 2 Te 3 phase. The extracted AH component of the MnBi 2 Te 4 phase shows a clear even-odd layer-dependent behavior. Our studies reveal insights on how to optimize the MBE growth conditions to improve the quality of MnBi 2 Te 4 films.

Published
2021
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49. Atomically Thin CrCl 3 : An In-Plane Layered Antiferromagnetic Insulator.

Author

Cai X, Song T, Wilson NP, Clark G, He M, Zhang X, Taniguchi T, Watanabe K, Yao W, Xiao D, McGuire MA, Cobden DH, and Xu X

Abstract

The recent discovery of magnetism in atomically thin layers of van der Waals (vdW) crystals has created new opportunities for exploring magnetic phenomena in the two-dimensional (2D) limit. In most 2D magnets studied to date, the c-axis is an easy axis, so that at zero applied field the polarization of each layer is perpendicular to the plane. Here, we demonstrate that atomically thin CrCl 3 is a layered antiferromagnetic insulator with an easy-plane normal to the c-axis, that is, the polarization is in the plane of each layer and has no preferred direction within it. Ligand-field photoluminescence at 870 nm is observed down to the monolayer limit, demonstrating its insulating properties. We investigate the in-plane magnetic order using tunneling magnetoresistance in graphene/CrCl 3 /graphene tunnel junctions, establishing that the interlayer coupling is antiferromagnetic down to the bilayer. From the temperature dependence of the magnetoresistance, we obtain an effective magnetic phase diagram for the bilayer. Our result shows that CrCl 3 should be useful for studying the physics of 2D phase transitions and for making new kinds of vdW spintronic devices.

Published
2019
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50. Valley Manipulation by Optically Tuning the Magnetic Proximity Effect in WSe 2 /CrI 3 Heterostructures.

Author

Seyler KL, Zhong D, Huang B, Linpeng X, Wilson NP, Taniguchi T, Watanabe K, Yao W, Xiao D, McGuire MA, Fu KC, and Xu X

Abstract

Monolayer valley semiconductors, such as tungsten diselenide (WSe 2 ), possess valley pseudospin degrees of freedom that are optically addressable but degenerate in energy. Lifting the energy degeneracy by breaking time-reversal symmetry is vital for valley manipulation. This has been realized by directly applying magnetic fields or via pseudomagnetic fields generated by intense circularly polarized optical pulses. However, sweeping large magnetic fields is impractical for devices, and the pseudomagnetic fields are only effective in the presence of ultrafast laser pulses. The recent rise of two-dimensional (2D) magnets unlocks new approaches to controlling valley physics via van der Waals heterostructure engineering. Here, we demonstrate the wide continuous tuning of the valley polarization and valley Zeeman splitting with small changes in the laser-excitation power in heterostructures formed by monolayer WSe 2 and 2D magnetic chromium triiodide (CrI 3 ). The valley manipulation is realized via the optical control of the CrI 3 magnetization, which tunes the magnetic exchange field over a range of 20 T. Our results reveal a convenient new path toward the optical control of valley pseudospins and van der Waals magnetic heterostructures.

Published
2018
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