1
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Zhou H, Feng Q, Sun C, Li Y, Tao W, Tang W, Li L, Shi E, Nan G, Zhu H. Robust excitonic light emission in 2D tin halide perovskites by weak excited state polaronic effect. Nat Commun 2024; 15:8541. [PMID: 39358359 PMCID: PMC11447268 DOI: 10.1038/s41467-024-52952-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Accepted: 09/26/2024] [Indexed: 10/04/2024] Open
Abstract
2D perovskites hold immense promise in optoelectronics due to their strongly bound electron-hole pairs (i.e., excitons). While exciton polaron from interplay between exciton and lattice has been established in 2D lead-based perovskites, the exciton nature and behavior in the emerging 2D tin-based perovskites remains unclear. By combining spin-resolved ultrafast spectroscopy and sophisticated theoretical calculations, we reveal 2D tin-based perovskites as genuine excitonic semiconductors with weak polaronic screening effect and persistent Coulomb interaction, thanks to weak exciton-phonon coupling. We determine an excited state exciton binding energy of ~0.18 eV in n = 2 tin iodide perovskites, nearly twice of that in lead counterpart, despite of same large value of ~0.2 eV from steady state measurement. This finding emphasizes the pivotal role of excited state polaronic effect in these materials. The robust excitons in 2D tin-based perovskites exhibit excitation power-insensitive, high-efficiency and color-purity emission, rendering them superior for light-emitting applications.
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Affiliation(s)
- Hongzhi Zhou
- Department of Chemistry, State Key Laboratory of Extreme Photonics and Instrumentation, Zhejiang Key Laboratory of Excited State Energy Conversion and Storage, Zhejiang University, Hangzhou, China
| | - Qingjie Feng
- Department of Physics, Zhejiang Normal University, Jinhua, Zhejiang, China
| | - Cheng Sun
- Department of Chemistry, State Key Laboratory of Extreme Photonics and Instrumentation, Zhejiang Key Laboratory of Excited State Energy Conversion and Storage, Zhejiang University, Hangzhou, China
- ZJU-Hangzhou Global Scientific and Technological Innovation Center, Hangzhou, Zhejiang, China
| | - Yahui Li
- Research Center for Industries of the Future and School of Engineering, Westlake University, Hangzhou, China
| | - Weijian Tao
- Department of Chemistry, State Key Laboratory of Extreme Photonics and Instrumentation, Zhejiang Key Laboratory of Excited State Energy Conversion and Storage, Zhejiang University, Hangzhou, China
| | - Wei Tang
- State Key Laboratory of Extreme Photonics and Instrumentation, College of Optical Science and Engineering, Zhejiang University, Hangzhou, China
| | - Linjun Li
- State Key Laboratory of Extreme Photonics and Instrumentation, College of Optical Science and Engineering, Zhejiang University, Hangzhou, China
| | - Enzheng Shi
- Research Center for Industries of the Future and School of Engineering, Westlake University, Hangzhou, China
| | - Guangjun Nan
- Department of Physics, Zhejiang Normal University, Jinhua, Zhejiang, China.
| | - Haiming Zhu
- Department of Chemistry, State Key Laboratory of Extreme Photonics and Instrumentation, Zhejiang Key Laboratory of Excited State Energy Conversion and Storage, Zhejiang University, Hangzhou, China.
- ZJU-Hangzhou Global Scientific and Technological Innovation Center, Hangzhou, Zhejiang, China.
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2
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Xiang B, Wang R, Chen Y, Wang Y, Qin T, Zhang M, Watanabe K, Taniguchi T, Duan W, Tang P, Liu H, Xiong Q. Chirality-Dependent Dynamic Evolution for Trions in Monolayer WS 2. NANO LETTERS 2024; 24:6592-6600. [PMID: 38787539 DOI: 10.1021/acs.nanolett.4c01082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2024]
Abstract
Monolayer transition metal dichalcogenides exhibit valley-dependent excitonic characters with a large binding energy, acting as the building block for future optoelectronic functionalities. Herein, combined with pump-probe ultrafast transient transmission spectroscopy and theoretical simulations, we reveal the chirality-dependent trion dynamics in h-BN encapsulated monolayer tungsten disulfide. By resonantly pumping trions in a single valley and monitoring their temporal evolution, we identify the temperature-dependent competition between two relaxation channels driven by chirality-dependent scattering processes. At room temperature, the phonon-assisted upconversion process predominates, converting excited trions to excitons within the same valley on a sub-picosecond (ps) time scale. As temperature decreases, this process becomes less efficient, while alternative channels, notably valley depolarization process for trions, assume importance, leading to an increase of trion density in the unpumped valley within a ps time scale. Our time-resolved valley-contrast results provide a comprehensive insight into trion dynamics in 2D materials, thereby advancing the development of novel valleytronic devices.
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Affiliation(s)
- Baixu Xiang
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing,100084, P. R. China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, P. R. China
| | - Renqi Wang
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing,100084, P. R. China
| | - Yuzhong Chen
- Beijing Academy of Quantum Information Sciences, Beijing 100193, P. R. China
| | - Yubin Wang
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing,100084, P. R. China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, P. R. China
| | - Tingxiao Qin
- Beijing Academy of Quantum Information Sciences, Beijing 100193, P. R. China
| | - Mengdi Zhang
- Beijing Academy of Quantum Information Sciences, Beijing 100193, P. R. China
| | - Kenji Watanabe
- Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Wenhui Duan
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing,100084, P. R. China
- Institute for Advanced Study, Tsinghua University, Beijing 100084, P. R. China
- Frontier Science Center for Quantum Information, Beijing, 100084, P. R. China
| | - Peizhe Tang
- School of Materials Science and Engineering, Beihang University, Beijing 100191, P. R. China
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, 22761 Hamburg, Germany
| | - Haiyun Liu
- Beijing Academy of Quantum Information Sciences, Beijing 100193, P. R. China
| | - Qihua Xiong
- State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing,100084, P. R. China
- Beijing Academy of Quantum Information Sciences, Beijing 100193, P. R. China
- Frontier Science Center for Quantum Information, Beijing, 100084, P. R. China
- Collaborative Innovation Center of Quantum Matter, Beijing, 100084, P.R. China
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3
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Song M, Wang H, Hu Z, Zhang Y, Liu T, Wang H. The Role of Polaronic States on the Spin Dynamics in Solution-Processed Two-Dimensional Layered Perovskite with Different Layer Thickness. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2302554. [PMID: 37395386 PMCID: PMC10502664 DOI: 10.1002/advs.202302554] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 06/08/2023] [Indexed: 07/04/2023]
Abstract
2D lead halide perovskites (LHPs) show strong excitonic and spin-orbit coupling effects, generating a facile spin injection. Besides, they possess a polaron character due to the soft crystal lattice, which can prolong the spin lifetime, making them favorable materials for spintronic applications. Here, the spin dynamics of 2D PEA2 PbI4 (MAPbI3 )n -l thin films with different layers by temperature- and pump fluence-dependent circularly polarization-resolved transient absorption (TA) measurements is studied. These results indicate that the spin depolarization mechanism is gradually converted from the Maialle-Silva-Sham (MSS) mechanism to the polaronic states protection mechanism with the layer number increasing from = 1 to 3, which is determined by the interplay between the strength of Coulomb exchange interaction and the strength of polaronic effect. While for ≥ 4, the Elliot-Yafet (EY) impurities mechanism is proposed, in which the formed polaronic states with free charge carriers no longer play the protective role.
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Affiliation(s)
- Mu‐Sen Song
- State Key Laboratory of Integrated OptoelectronicsCollege of Electronic Science and EngineeringJilin University2699 Qianjin StreetChangchun130012China
| | - Hai Wang
- State Key Laboratory of Integrated OptoelectronicsCollege of Electronic Science and EngineeringJilin University2699 Qianjin StreetChangchun130012China
| | - Zi‐Fan Hu
- State Key Laboratory of Integrated OptoelectronicsCollege of Electronic Science and EngineeringJilin University2699 Qianjin StreetChangchun130012China
| | - Yu‐Peng Zhang
- State Key Laboratory of Integrated OptoelectronicsCollege of Electronic Science and EngineeringJilin University2699 Qianjin StreetChangchun130012China
| | - Tian‐Yu Liu
- State Key Laboratory of Integrated OptoelectronicsCollege of Electronic Science and EngineeringJilin University2699 Qianjin StreetChangchun130012China
| | - Hai‐Yu Wang
- State Key Laboratory of Integrated OptoelectronicsCollege of Electronic Science and EngineeringJilin University2699 Qianjin StreetChangchun130012China
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4
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Cai R, Wadgaonkar I, Lim JWM, Dal Forno S, Giovanni D, Feng M, Ye S, Battiato M, Sum TC. Zero-field quantum beats and spin decoherence mechanisms in CsPbBr 3 perovskite nanocrystals. Nat Commun 2023; 14:2472. [PMID: 37120626 PMCID: PMC10148794 DOI: 10.1038/s41467-023-37721-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 03/24/2023] [Indexed: 05/01/2023] Open
Abstract
Coherent optical manipulation of exciton states provides a fascinating approach for quantum gating and ultrafast switching. However, their coherence time for incumbent semiconductors is highly susceptible to thermal decoherence and inhomogeneous broadening effects. Here, we uncover zero-field exciton quantum beating and anomalous temperature dependence of the exciton spin lifetimes in CsPbBr3 perovskite nanocrystals (NCs) ensembles. The quantum beating between two exciton fine-structure splitting (FSS) levels enables coherent ultrafast optical control of the excitonic degree of freedom. From the anomalous temperature dependence, we identify and fully parametrize all the regimes of exciton spin depolarization, finding that approaching room temperature, it is dominated by a motional narrowing process governed by the exciton multilevel coherence. Importantly, our results present an unambiguous full physical picture of the complex interplay of the underlying spin decoherence mechanisms. These intrinsic exciton FSS states in perovskite NCs present fresh opportunities for spin-based photonic quantum technologies.
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Affiliation(s)
- Rui Cai
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - Indrajit Wadgaonkar
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - Jia Wei Melvin Lim
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
- ERI@N, Interdisciplinary Graduate School, Nanyang Technological University, Singapore, Singapore
| | - Stefano Dal Forno
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - David Giovanni
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - Minjun Feng
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - Senyun Ye
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - Marco Battiato
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore.
| | - Tze Chien Sum
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore.
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5
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Kunin A, Chernov S, Bakalis J, Li Z, Cheng S, Withers ZH, White MG, Schönhense G, Du X, Kawakami RK, Allison TK. Momentum-Resolved Exciton Coupling and Valley Polarization Dynamics in Monolayer WS_{2}. PHYSICAL REVIEW LETTERS 2023; 130:046202. [PMID: 36763432 DOI: 10.1103/physrevlett.130.046202] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Accepted: 12/22/2022] [Indexed: 06/18/2023]
Abstract
Using time- and angle-resolved photoemission, we present momentum- and energy-resolved measurements of exciton coupling in monolayer WS_{2}. We observe strong intravalley coupling between the B_{1s} exciton and A_{n>1} states. Our measurements indicate that the dominant valley depolarization mechanism conserves the exciton binding energy and momentum. While this conservation is consistent with Coulomb exchange-driven valley depolarization, we do not observe a momentum or energy dependence to the depolarization rate as would be expected for the exchange-based mechanism.
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Affiliation(s)
- Alice Kunin
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, USA
| | - Sergey Chernov
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, USA
| | - Jin Bakalis
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, USA
| | - Ziling Li
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Shuyu Cheng
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Zachary H Withers
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA
| | - Michael G White
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, USA
- Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Gerd Schönhense
- Johannes Gutenberg-Universität, Institut für Physik, D-55099 Mainz, Germany
| | - Xu Du
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA
| | - Roland K Kawakami
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Thomas K Allison
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794, USA
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA
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6
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Cilibrizzi P, Liu X, Zhang P, Wang C, Li Q, Yang S, Zhang X. Self-Induced Valley Bosonic Stimulation of Exciton Polaritons in a Monolayer Semiconductor. PHYSICAL REVIEW LETTERS 2023; 130:036902. [PMID: 36763375 DOI: 10.1103/physrevlett.130.036902] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2021] [Accepted: 11/18/2022] [Indexed: 06/18/2023]
Abstract
The newly discovered valley degree of freedom in atomically thin two-dimensional transition metal dichalcogenides offers a promising platform to explore rich nonlinear physics, such as spinor Bose-Einstein condensate and novel valleytronics applications. However, the critical nonlinear effect, such as valley polariton bosonic stimulation, has long remained an unresolved challenge due to the generation of limited polariton ground state densities necessary to induce the stimulated scattering of polaritons in specific valleys. Here, we report the self-induced valley bosonic stimulation of exciton polaritons via spin-valley locking in a WS_{2} monolayer microcavity. This is achieved by the resonant injection of valley polaritons at specific energy and wave vector, which allows spin-polarized polaritons to efficiently populate their ground state and induce a valley-dependent bosonic stimulation. As a result, we observe the nonlinear self-amplification of polariton emission from the valley-dependent ground state. Our finding paves the way for the investigation of spin ordering and phase transitions in transition metal dichalcogenides polariton Bose-Einstein condensate, offering a promising route for the realization of polariton spin lattices in moiré polariton systems and spin lasers.
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Affiliation(s)
- Pasquale Cilibrizzi
- NSF Nanoscale Science and Engineering Center, University of California, Berkeley, California 94720, USA
| | - Xiaoze Liu
- NSF Nanoscale Science and Engineering Center, University of California, Berkeley, California 94720, USA
| | - Peiyao Zhang
- NSF Nanoscale Science and Engineering Center, University of California, Berkeley, California 94720, USA
| | - Chenzhe Wang
- NSF Nanoscale Science and Engineering Center, University of California, Berkeley, California 94720, USA
| | - Quanwei Li
- NSF Nanoscale Science and Engineering Center, University of California, Berkeley, California 94720, USA
| | - Sui Yang
- NSF Nanoscale Science and Engineering Center, University of California, Berkeley, California 94720, USA
| | - Xiang Zhang
- NSF Nanoscale Science and Engineering Center, University of California, Berkeley, California 94720, USA
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7
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Godiksen RH, Wang S, Raziman TV, Rivas JG, Curto AG. Impact of indirect transitions on valley polarization in WS 2 and WSe 2. NANOSCALE 2022; 14:17761-17769. [PMID: 36426625 PMCID: PMC9730303 DOI: 10.1039/d2nr04800k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Accepted: 11/21/2022] [Indexed: 06/16/2023]
Abstract
Controlling the momentum of carriers in semiconductors, known as valley polarization, is a new resource for optoelectronics and information technologies. Materials exhibiting high polarization are needed for valley-based devices. Few-layer WS2 shows a remarkable spin-valley polarization above 90%, even at room temperature. In stark contrast, polarization is absent for few-layer WSe2 despite the expected material similarities. Here, we explain the origin of valley polarization in both materials based on the interplay between two indirect optical transitions. We show that the relative energy minima at the Λ- and K-valleys in the conduction band determine the spin-valley polarization of the direct K-K transition. Polarization appears as the energy of the K-valley rises above the Λ-valley as a function of temperature and number of layers. Our results advance the understanding of the high spin-valley polarization in WS2. This insight will impact the design of both passive and tunable valleytronic devices operating at room temperature.
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Affiliation(s)
- Rasmus H Godiksen
- Dep. Applied Physics and Institute for Photonic Integration, Eindhoven University of Technology, Eindhoven, The Netherlands.
| | - Shaojun Wang
- Dep. Applied Physics and Institute for Photonic Integration, Eindhoven University of Technology, Eindhoven, The Netherlands.
- MOE Key Lab. of Modern Optical Technologies and Jiangsu Key Lab. of Advanced Optical Manufacturing Technologies, School of Optoelectronic Science and Engineering, Soochow University, Suzhou 215006, China
| | - T V Raziman
- Dep. Applied Physics and Institute for Photonic Integration, Eindhoven University of Technology, Eindhoven, The Netherlands.
| | - Jaime Gómez Rivas
- Dep. Applied Physics and Institute for Photonic Integration, Eindhoven University of Technology, Eindhoven, The Netherlands.
| | - Alberto G Curto
- Dep. Applied Physics and Institute for Photonic Integration, Eindhoven University of Technology, Eindhoven, The Netherlands.
- Photonics Research Group, Ghent University-imec, Ghent, Belgium
- Center for Nano- and Biophotonics, Ghent University, Ghent, Belgium
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8
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Yumoto G, Sekiguchi F, Hashimoto R, Nakamura T, Wakamiya A, Kanemitsu Y. Rapidly expanding spin-polarized exciton halo in a two-dimensional halide perovskite at room temperature. SCIENCE ADVANCES 2022; 8:eabp8135. [PMID: 35905182 PMCID: PMC9337763 DOI: 10.1126/sciadv.abp8135] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Accepted: 06/14/2022] [Indexed: 06/15/2023]
Abstract
Monitoring of the spatially resolved exciton spin dynamics in two-dimensional semiconductors has revealed the formation of a spatial pattern and long-range transport of the spin-polarized excitons, which holds promise for exciton-based spin-optoelectronic applications. However, the spatial evolution has been restricted to cryogenic temperatures because of the short exciton spin relaxation times at room temperature. Here, we report that two-dimensional halide perovskites can overcome this limitation owing to their relatively long exciton spin relaxation times and substantial exciton-exciton interactions. We demonstrate the emergence of a halo-like spatial profile in spin-polarized exciton population and its ultrafast expansion at room temperature by performing time-resolved Faraday rotation imaging of spin-polarized excitons in two-dimensional perovskite (C4H9NH3)2(CH3NH3)3Pb4I13. Exciton-exciton exchange interactions induce density-dependent nonlinear relaxation and ultrafast transport of exciton spins and give rise to a rapidly expanding halo-like spatial pattern. The density-dependent spatial control suggests the potential of using two-dimensional halide perovskites for spin-optoelectronic applications.
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9
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Tao W, Zhang Y, Zhu H. Dynamic Exciton Polaron in Two-Dimensional Lead Halide Perovskites and Implications for Optoelectronic Applications. Acc Chem Res 2022; 55:345-353. [PMID: 35043614 DOI: 10.1021/acs.accounts.1c00626] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
ConspectusThe past few years have witnessed an exciting revival of the research interest in two-dimensional (2D) lead halide perovskites. The renaissance is strongly motivated by the great success of their three-dimensional (3D) counterparts in optoelectronic applications. Different from 3D lead halide perovskites where free carriers are generated upon photoexcitation, 2D lead halide perovskites experience weaker dielectric screening and stronger quantum confinement effects. Therefore, strongly bound excitons with binding energy of up to a few hundreds of meV are considered to be the main excited-state species responsible for optoelectronic processes in 2D perovskites. In addition to strong excitonic effects, polaronic effects are also inherent in the soft and anharmonic lattice of lead halide perovskites, and polaronic structural relaxation is found to strongly renormalize carrier excited-state behaviors. For example, ferroelectric large polaron formation and liquid-like solvation of band edge carriers are proposed to account for the exceptional properties of 3D lead halide perovskites. As for 2D lead halide perovskites, polaronic characteristics have also been observed in exciton spectral characters, but how the interplay between excitonic effect and polaronic effect redefines the nature of exciton polarons and their excited-state behaviors still remains largely unexplored.In this Account, we discuss our recent experimental findings about the excited-state properties of exciton polarons in 2D lead halide perovskites. We begin our discussion by introducing a conventional view of strongly bound excitons in 2D lead halide perovskites with large exciton binding energy, which is typically estimated from steady-state absorption spectra. However, owing to the soft and anharmonic lattice, excitons in 2D lead halide perovskites exhibit significant polaronic characters and exist as exciton polarons. It is still unclear how polaronic effects would affect the exciton properties in 2D lead halide perovskites, especially in their excited-state dynamics. By probing exchange interaction, we found that both intra- and inter-exciton Coulomb interaction strengths are substantially weakened by the polaronic screening effect, which is manifested as (1) a counterintuitively longer exciton spin lifetime by almost an order of magnitude or a smaller intraexcitonic interaction strength with temperature increasing from 80 to 340 K and (2) an order of magnitude smaller interexcitonic interaction strength compared to another prototypical 2D semiconductor named transition-metal dichalcogenides (TMDCs) with a comparable steady-state exciton binding energy. We further discuss the interplay between the long- and short-range exciton-phonon interaction and conclude that the exciton-phonon interaction strength is in an intermediate regime and the exciton polaron is momentarily trapped in 2D perovskites, that is, a dynamic exciton polaron.Finally, we highlight prospective opportunities with ligand and cation engineering to regulate the exciton-phonon interaction and exciton polaron properties in 2D perovskites, which have strong implications toward future rational design for 2D perovskite-based efficient photovoltaics or light-emitting devices with high color purity.
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Affiliation(s)
- Weijian Tao
- State Key Laboratory of Modern Optical Instrumentation, Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310027, China
| | - Yao Zhang
- State Key Laboratory of Modern Optical Instrumentation, Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310027, China
| | - Haiming Zhu
- State Key Laboratory of Modern Optical Instrumentation, Key Laboratory of Excited-State Materials of Zhejiang Province, Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310027, China
- Zhejiang University-Hangzhou Global Scientific and Technological Innovation Center, Hangzhou 310014, P. R. China
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10
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Lloyd LT, Wood RE, Mujid F, Sohoni S, Ji KL, Ting PC, Higgins JS, Park J, Engel GS. Sub-10 fs Intervalley Exciton Coupling in Monolayer MoS 2 Revealed by Helicity-Resolved Two-Dimensional Electronic Spectroscopy. ACS NANO 2021; 15:10253-10263. [PMID: 34096707 DOI: 10.1021/acsnano.1c02381] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The valley pseudospin at the K and K' high-symmetry points in monolayer transition metal dichalcogenides (TMDs) has potential as an optically addressable degree of freedom in next-generation optoelectronics. However, intervalley scattering and relaxation of charge carriers leads to valley depolarization and limits practical applications. In addition, enhanced Coulomb interactions lead to pronounced excitonic effects that dominate the optical response and initial valley depolarization dynamics but complicate the interpretation of ultrafast spectroscopic experiments at short time delays. Employing broadband helicity-resolved two-dimensional electronic spectroscopy (2DES), we observe ultrafast (∼10 fs) intervalley coupling between all A and B valley exciton states that results in a complete breakdown of the valley index in large-area monolayer MoS2 films. These couplings and subsequent dynamics exhibit minimal excitation fluence or temperature dependence and are robust toward changes in sample grain size and inherent strain. Our observations strongly suggest that this direct intervalley coupling on the time scale of optical excitation is an inherent property of large-area MoS2 distinct from dynamic carrier or exciton scattering, phonon-driven processes, and multiexciton effects. This ultrafast intervalley coupling poses a fundamental challenge for exciton-based valleytronics in monolayer TMDs and must be overcome to fully realize large-area valleytronic devices.
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Affiliation(s)
- Lawson T Lloyd
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Ryan E Wood
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Fauzia Mujid
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
| | - Siddhartha Sohoni
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Karen L Ji
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Po-Chieh Ting
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Jacob S Higgins
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Jiwoong Park
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
- Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, United States
| | - Gregory S Engel
- Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
- James Franck Institute, The University of Chicago, Chicago, Illinois 60637, United States
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
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11
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Jeong TY, Bae S, Lee SY, Jung S, Kim YH, Yee KJ. Valley depolarization in monolayer transition-metal dichalcogenides with zone-corner acoustic phonons. NANOSCALE 2020; 12:22487-22494. [PMID: 33169781 DOI: 10.1039/d0nr04761a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Although single-layer transition-metal dichalcogenides with novel valley functionalities are a promising candidate to realize valleytronic devices, the essential understanding of valley depolarization mechanisms is still incomplete. Based on pump-probe experiments performed for MoSe2 and WSe2 monolayers and corroborating analysis from density functional calculations, we demonstrate that coherent phonons at the K-point of the Brillouin zone can effectively mediate the valley transfer of electron carriers. In the MoSe2 monolayer case, we identify this mode as the flexural acoustic ZA(K) mode, which has broken inversion symmetry and thus can enable electron spin-flip during valley transfer. On the other hand, in the monolayer WSe2 case where spin-preserving inter-valley relaxations are preferred, coherent LA(K) phonons with even inversion symmetry are efficiently generated. These findings establish that while the specifics of inter-valley relaxations depend on the spin alignments of energy bands, the K-point phonons should be taken into account as an effective valley depolarization pathway in transition metal dichalcogenide monolayers.
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Affiliation(s)
- Tae-Young Jeong
- Department of Physics, Chungnam National University, Daejeon 34134, Republic of Korea.
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12
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Tao W, Zhou Q, Zhu H. Dynamic polaronic screening for anomalous exciton spin relaxation in two-dimensional lead halide perovskites. SCIENCE ADVANCES 2020; 6:6/47/eabb7132. [PMID: 33219022 PMCID: PMC7679171 DOI: 10.1126/sciadv.abb7132] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Accepted: 10/01/2020] [Indexed: 06/07/2023]
Abstract
Two-dimensional lead halide perovskites with confined excitons have shown exciting potentials in optoelectronic applications. It is intriguing but unclear how the soft and polar lattice redefines excitons in layered perovskites. Here, we reveal the intrinsic exciton properties by investigating exciton spin dynamics, which provides a sensitive probe to exciton coulomb interactions. Compared to transition metal dichalcogenides with comparable exciton binding energy, we observe orders of magnitude smaller exciton-exciton interaction and, counterintuitively, longer exciton spin lifetime at higher temperature. The anomalous spin dynamics implies that excitons exist as exciton polarons with substantially weakened inter- and intra-excitonic interactions by dynamic polaronic screening. The combination of strong light matter interaction from reduced dielectric screening and weakened inter-/intra-exciton interaction from dynamic polaronic screening explains their exceptional performance and provides new rules for quantum-confined optoelectronic and spintronic systems.
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Affiliation(s)
- Weijian Tao
- State Key Laboratory of Modern Optical Instrumentation, Centre for Chemistry of High-Performance and Novel Materials, Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310027, China
| | - Qiaohui Zhou
- State Key Laboratory of Modern Optical Instrumentation, Centre for Chemistry of High-Performance and Novel Materials, Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310027, China
| | - Haiming Zhu
- State Key Laboratory of Modern Optical Instrumentation, Centre for Chemistry of High-Performance and Novel Materials, Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang 310027, China.
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13
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Shi J, Baldini E, Latini S, Sato SA, Zhang Y, Pein BC, Shen PC, Kong J, Rubio A, Gedik N, Nelson KA. Room Temperature Terahertz Electroabsorption Modulation by Excitons in Monolayer Transition Metal Dichalcogenides. NANO LETTERS 2020; 20:5214-5220. [PMID: 32539410 DOI: 10.1021/acs.nanolett.0c01134] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The interaction between off-resonant laser pulses and excitons in monolayer transition metal dichalcogenides is attracting increasing interest as a route for the valley-selective coherent control of the exciton properties. Here, we extend the classification of the known off-resonant phenomena by unveiling the impact of a strong THz field on the excitonic resonances of monolayer MoS2. We observe that the THz pump pulse causes a selective modification of the coherence lifetime of the excitons, while keeping their oscillator strength and peak energy unchanged. We rationalize these results theoretically by invoking a hitherto unobserved manifestation of the Franz-Keldysh effect on an exciton resonance. As the modulation depth of the optical absorption reaches values as large as 0.05 dB/nm at room temperature, our findings open the way to the use of semiconducting transition metal dichalcogenides as compact and efficient platforms for high-speed electroabsorption devices.
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Affiliation(s)
- Jiaojian Shi
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Edoardo Baldini
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Simone Latini
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, 22761 Hamburg, Germany
| | - Shunsuke A Sato
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, 22761 Hamburg, Germany
- Center for Computational Sciences, University of Tsukuba, Tsukuba 305-8577, Japan
| | - Yaqing Zhang
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Brandt C Pein
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Pin-Chun Shen
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Jing Kong
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Angel Rubio
- Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, 22761 Hamburg, Germany
- Nano-Bio Spectroscopy Group, Departamento de Fisica de Materiales, Universidad del País Vasco, 20018 San Sebastían, Spain
- Center for Computational Quantum Physics, Simons Foundation Flatiron Institute, New York, New York 10010, United States
| | - Nuh Gedik
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Keith A Nelson
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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14
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Katsch F, Selig M, Knorr A. Exciton-Scattering-Induced Dephasing in Two-Dimensional Semiconductors. PHYSICAL REVIEW LETTERS 2020; 124:257402. [PMID: 32639791 DOI: 10.1103/physrevlett.124.257402] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 01/25/2020] [Accepted: 06/01/2020] [Indexed: 05/13/2023]
Abstract
Enhanced Coulomb interactions in monolayer transition metal dichalcogenides cause tightly bound electron-hole pairs (excitons) that dominate their linear and nonlinear optical response. The latter includes bleaching, energy renormalizations, and higher-order Coulomb correlation effects like biexcitons and excitation-induced dephasing. While the first three are extensively studied, no theoretical footing for excitation-induced dephasing in exciton-dominated semiconductors is available so far. In this Letter, we present microscopic calculations based on excitonic Heisenberg equations of motion and identify the coupling of optically pumped excitons to exciton-exciton scattering continua as the leading mechanism responsible for an optical-power-dependent linewidth broadening (excitation-induced dephasing) and sideband formation. Performing time-, momentum-, and energy-resolved simulations, we quantitatively evaluate the exciton-induced dephasing for the most common monolayer transition metal dichalcogenides and find an excellent agreement with recent experiments.
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Affiliation(s)
- Florian Katsch
- Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, 10623 Berlin, Germany
| | - Malte Selig
- Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, 10623 Berlin, Germany
| | - Andreas Knorr
- Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, 10623 Berlin, Germany
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15
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Liu W, Wang Y, Zheng B, Hwang M, Ji Z, Liu G, Li Z, Sorger VJ, Pan A, Agarwal R. Observation and Active Control of a Collective Polariton Mode and Polaritonic Band Gap in Few-Layer WS 2 Strongly Coupled with Plasmonic Lattices. NANO LETTERS 2020; 20:790-798. [PMID: 31846342 DOI: 10.1021/acs.nanolett.9b05056] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Two-dimensional semiconductors host excitons with very large oscillator strengths and binding energies due to significantly reduced carrier screening. Two-dimensional semiconductors integrated with optical cavities are emerging as a promising platform for studying strong light-matter interactions as a route to explore a variety of exotic many-body effects. Here, in few-layered WS2 coupled with plasmonic nanoparticle lattices, we observe the formation of a collective polaritonic mode near the exciton energy and the formation of a complete polariton band gap with energy scale comparable to the exciton-plasmon coupling strength. A coupled oscillator model reveals that the collective mode arises from the cooperative coupling of the excitons to the plasmonic lattice diffraction orders via exciton-exciton interactions, leading to ultrastrong coupling. The emergence of the collective mode is accompanied by a superlinear increase of the polariton mode splitting as a function of the square root of the exciton oscillator strength. The presence of these many body effects, which are enhanced in systems which lack bulk polarization, not only allows the formation of a collective mode with periodically varying field profiles, but also further enhances the exciton-plasmon coupling. By integrating the hybrid WS2-plasmonic lattice device with a field-effect transistor, we demonstrate active tuning of the collective mode and the polariton band gap. We also report electrically tunable waveguiding in the polariton band gap region through a line defect, which can be turned off with gate bias that can extinguish the collective mode and the polariton band gap. These systems provide new opportunities for obtaining a deeper and systematic understanding of many body cooperative phenomena in two-dimensional materials coupled with periodic photonic systems and for designing more complex and actively controllable polaritonic devices including switchable polariton lasers, waveguides, and optical logical elements.
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Affiliation(s)
- Wenjing Liu
- Department of Materials Science and Engineering , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - Yuhui Wang
- Department of Materials Science and Engineering , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - Biyuan Zheng
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, School of Physics and Electronic Science , Hunan University , Changsha , Hunan 410082 , P. R. China
| | - Minsoo Hwang
- Department of Materials Science and Engineering , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - Zhurun Ji
- Department of Materials Science and Engineering , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - Gerui Liu
- Department of Materials Science and Engineering , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
| | - Ziwei Li
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, School of Physics and Electronic Science , Hunan University , Changsha , Hunan 410082 , P. R. China
| | - Volker J Sorger
- Department of Electrical and Computer Engineering , George Washington University 800 22nd St., Science & Engineering Hall , Washington, D.C. 20052 , United States
| | - Anlian Pan
- Key Laboratory for Micro-Nano Physics and Technology of Hunan Province, School of Physics and Electronic Science , Hunan University , Changsha , Hunan 410082 , P. R. China
| | - Ritesh Agarwal
- Department of Materials Science and Engineering , University of Pennsylvania , Philadelphia , Pennsylvania 19104 , United States
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16
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Iyer V, Chen YP, Xu X. Ultrafast Surface State Spin-Carrier Dynamics in the Topological Insulator Bi_{2}Te_{2}Se. PHYSICAL REVIEW LETTERS 2018; 121:026807. [PMID: 30085694 DOI: 10.1103/physrevlett.121.026807] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 05/06/2018] [Indexed: 06/08/2023]
Abstract
Topological insulators are promising candidates for optically driven spintronic devices, because photoexcitation of spin polarized surface states is governed by angular momentum selection rules. We carry out femtosecond midinfrared spectroscopy on thin films of the topological insulator Bi_{2}Te_{2}Se, which has a higher surface state conductivity compared to conventionally studied Bi_{2}Se_{3} and Bi_{2}Te_{3}. Both charge and spin dynamics are probed utilizing circularly polarized light. With a sub-band-gap excitation, clear helicity-dependent dynamics is observed only in thin (<20 nm) flakes. On the other hand, such dependence is observed for both thin and thick flakes with above-band-gap excitation. The helicity dependence is attributed to asymmetric excitation of the Dirac-like surface states. The observed long-lasting asymmetry over 10 ps even at room temperature indicates low backscattering of surface state carriers which can be exploited for spintronic devices.
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Affiliation(s)
- Vasudevan Iyer
- Department of Mechanical Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
| | - Yong P Chen
- Department of Physics and Astronomy and School of Electrical and Computer Engineering and Birck Nanotechnology Center and Purdue Quantum Center, Purdue University, West Lafayette, Indiana 47907, USA
| | - Xianfan Xu
- Department of Mechanical Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
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