1
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Zhang Q, Liu T, Shi Z, Zheng Z, Lv C, Wang X, Zhang Y. Narrowband TADF emitters with high utilization of triplet excitons: theoretical insights and molecular design. Phys Chem Chem Phys 2024; 26:5147-5155. [PMID: 38259229 DOI: 10.1039/d3cp05439j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Narrowband emitters with thermally activated delayed fluorescence (TADF) features, known as multi-resonant TADF (MR-TADF) emitters, are drawing increasing research interest owing to their properties of high efficiency and excellent color purity. However, MR-TADF-based devices often face serious efficiency roll-off at high luminance intensity, which could be attributed to undesired triplet-triplet annihilation (TTA) caused by the structural planarity and relatively small reverse intersystem crossing rate constants (krisc) of MR-TADF emitters. Herein, combining a sp3-C inserted strategy to suppress harmful bimolecular interactions and chalcogens to improve the krisc, a series of asymmetric narrowband emitters, namely, DMAC-O, DMAC-S, and DMAC-Se, have been theoretically designed to break the slow rate-limiting step of krisc of experimental BN-DMAC. For comparison, both O and Se atoms were doped into the MR skeleton to substitute two sp3-inserted units, yielding BN-O-Se. The combination of TD-DFT and the wavefunction-based STEOM-DLPNO-CCSD approach exhibits that those asymmetric molecules are promising for simultaneously exhibiting narrow emission spectral full-width at half-maximums (FWHMs) and high luminous efficiencies. The contributions of chalcogens to hole distributions result in red-shifted fluorescent peaks, and the asymmetric strategy also helps with twisted molecular configuration, which is beneficial for suppressing unfavorable TTA. Furthermore, the incorporation of chalcogens is sufficient to promote the intersystem crossing and reverse intersystem crossing channels of asymmetric emitters. More importantly, the doped heavy Se atom results in a significantly increased krisc of 2.32 × 106 s-1 for DMAC-Se, which is more than 200 times larger than 1.09 × 104 s-1 of pristine BN-DMAC. These results suggest that the combination of the heavy Se atom and an sp3-inserted unit is a feasible strategy for achieving poor planarity and significantly enhancing krisc, which will help in harvesting triplet excitons, thereby inhibiting efficiency roll-off in corresponding narrowband devices.
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Affiliation(s)
- Qing Zhang
- Department of Materials Chemistry, Huzhou University, East 2nd Ring Rd. No. 759, Huzhou, 313000, People's Republic of China.
| | - Tao Liu
- Department of Materials Chemistry, Huzhou University, East 2nd Ring Rd. No. 759, Huzhou, 313000, People's Republic of China.
| | - Zhouyang Shi
- Zhejiang Jiuhe Geological and Ecological Environment Planning and Design Co., LTD, Huzhou, 313002, People's Republic of China
| | - Zhong Zheng
- Anji Branch of Huzhou Ecological Environment Bureau, Huzhou, 313300, People's Republic of China
| | - Chunyan Lv
- Department of Materials Chemistry, Huzhou University, East 2nd Ring Rd. No. 759, Huzhou, 313000, People's Republic of China.
| | - Xin Wang
- Henan-Macquarie University Joint Centre for Biomedical Innovation, Henan Key Laboratory of Brain Targeted Bio-nanomedicine, School of Life Sciences, Henan University, Kaifeng, Henan, 475004, People's Republic of China.
| | - Yujian Zhang
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Department of Chemistry, Zhejiang Normal University, Yingbin Road No. 688, Jinhua 321004, People's Republic of China.
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2
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Li P, Wang Z, Li W, Yuan J, Chen R. Design of Thermally Activated Delayed Fluorescence Materials with High Intersystem Crossing Efficiencies by Machine Learning-Assisted Virtual Screening. J Phys Chem Lett 2022; 13:9910-9918. [PMID: 36256799 DOI: 10.1021/acs.jpclett.2c02735] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Efficient intersystem crossing (ISC) and reverse ISC (RISC) processes are of vital significance for thermally activated delayed fluorescence (TADF) materials to achieve 100% internal quantum efficiency. However, it is challenging to rapidly predict the ISC/RISC rates of large amounts of TADF materials and screen promising candidates because of their flexible molecular design. Here, we perform virtual screening of 564 candidates constructed from 20 unique building blocks linking in D-A, D-π-A, and D-A-D (D') configurations using the established machine learning models of GBRT and RF-GBRT-KNN with the Pearson's correlation coefficients (r) of 0.89 and 0.82, respectively. Novel descriptors of ΔELL, Polar, and ΔETT for predicting ISC/RISC rates were proposed, and nine TADF molecules with the predicted ISC and RISC rates of >7 × 107 and 2 × 105 s-1, respectively, were revealed. We provide an efficient approach to predicting ISC and RISC rates of TADF molecules on a large scale, elucidating important building blocks and architectures to design high-performance optoelectronic materials for experimental explorations.
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Affiliation(s)
- Ping Li
- State Key Laboratory of Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, Nanjing210023, China
| | - Zijie Wang
- State Key Laboratory of Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, Nanjing210023, China
| | - Wenjing Li
- State Key Laboratory of Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, Nanjing210023, China
| | - Jie Yuan
- State Key Laboratory of Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, Nanjing210023, China
| | - Runfeng Chen
- State Key Laboratory of Organic Electronics and Information Displays & Institute of Advanced Materials (IAM), Nanjing University of Posts & Telecommunications, Nanjing210023, China
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3
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Kuroyama K, Matsuo S, Muramoto J, Yabunaka S, Valentin SR, Ludwig A, Wieck AD, Tokura Y, Tarucha S. Real-Time Observation of Charge-Spin Cooperative Dynamics Driven by a Nonequilibrium Phonon Environment. PHYSICAL REVIEW LETTERS 2022; 129:095901. [PMID: 36083670 DOI: 10.1103/physrevlett.129.095901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Accepted: 07/14/2022] [Indexed: 06/15/2023]
Abstract
We report on experimental observations of charge-spin cooperative dynamics of two-electron states in a GaAs double quantum dot located in a nonequilibrium phonon environment. When the phonon energy exceeds the lowest excitation energy in the quantum dot, the spin-flip rate of a single electron strongly enhances. In addition, originated from the spatial gradient of phonon density between the dots, the parallel spin states become more probable than the antiparallel ones. These results indicate that spin is essential for further demonstrations of single-electron thermodynamic systems driven by phonons, which will greatly contribute to understanding of the fundamental physics of thermoelectric devices.
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Affiliation(s)
- Kazuyuki Kuroyama
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
- Center for Emergent Materials Science (CEMS), RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
| | - Sadashige Matsuo
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- Center for Emergent Materials Science (CEMS), RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
- Japan Science and Technology Agency, PRESTO, 4-1-8 Honcho, Kawaguchi-shi, Saitama 332-0012, Japan
| | - Jo Muramoto
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | | | - Sascha R Valentin
- Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum, Germany
| | - Arne Ludwig
- Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum, Germany
| | - Andreas D Wieck
- Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum, Germany
| | - Yasuhiro Tokura
- Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan
| | - Seigo Tarucha
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- Center for Emergent Materials Science (CEMS), RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
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4
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Zhang Q, Cao Z. Packing Effect on Light Emission of Naphthyridine-Based Luminophor: Insights from Quantum Mechanics and Quantum Mechanics/Molecular Mechanics Calculations. J Phys Chem B 2021; 125:3005-3013. [PMID: 33721999 DOI: 10.1021/acs.jpcb.1c01557] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Luminescent properties of the naphthyridine-based luminophor, 2,7-di(9,9-dimethylacridin-10(9H)-yl)-1,8-naphthyridine (DMAC-ND), have been explored by using quantum mechanics and quantum mechanics/molecular mechanics calculations. Based on different packing models for DMAC-ND monomer in tetrahydrofuran (THF) solution and its crystal and amorphous aggregated states, the morphology dependence of light absorption and emission has been explored. Calculations reveal that the intersystem crossing rates (kisc) from S1 to T1 are comparable with their corresponding non-radiative decay rates (knr) from S1 to S0 in crystal and amorphous phases, while the kisc value in THF solution is 6 orders of magnitude smaller than its corresponding knr, suggesting that effective intersystem crossing (ISC) may occur only in the aggregated configurations. The predicted reverse intersystem crossing rates (krisc) are also comparable with their corresponding non-radiative decay rates from T1 to S0, and there would be an effective upconversion process in the aggregated state. The predicted krisc values show notable morphology and temperature dependences, and the aggregation and the increase in temperature can facilitate the reverse intersystem crossing process. Based on the independent gradient model and energy decomposition analysis, combined with the estimation of the Huang-Rhys factors, such remarkable packing effects on the luminescent properties of DMAC-ND can be ascribed into the strong intermolecular interactions and the restriction of low-frequency vibrations in the crystal and amorphous phases.
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Affiliation(s)
- Qing Zhang
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 360015, People's Republic of China
| | - Zexing Cao
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 360015, People's Republic of China
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5
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Urdampilleta M, Niegemann DJ, Chanrion E, Jadot B, Spence C, Mortemousque PA, Bäuerle C, Hutin L, Bertrand B, Barraud S, Maurand R, Sanquer M, Jehl X, De Franceschi S, Vinet M, Meunier T. Gate-based high fidelity spin readout in a CMOS device. NATURE NANOTECHNOLOGY 2019; 14:737-741. [PMID: 31086305 DOI: 10.1038/s41565-019-0443-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Accepted: 03/29/2019] [Indexed: 06/09/2023]
Abstract
The engineering of a compact qubit unit cell that embeds all quantum functionalities is mandatory for large-scale integration. In addition, these functionalities should present the lowest error rate possible to successfully implement quantum error correction protocols1. Electron spins in silicon quantum dots are particularly promising because of their high control fidelity2-5 and their potential compatibility with complementary metal-oxide-semiconductor industrial platforms6,7. However, an efficient and scalable spin readout scheme is still missing. Here we demonstrate a high fidelity and robust spin readout based on gate reflectometry in a complementary metal-oxide-semiconductor device that consists of a qubit dot and an ancillary dot coupled to an electron reservoir. This scalable method allows us to read out a spin in a single-shot manner with an average fidelity above 98% for a 0.5 ms integration time. To achieve such a fidelity, we combine radio-frequency gate reflectometry with a latched spin blockade mechanism that requires electron exchange between the ancillary dot and the reservoir. We show that the demonstrated high readout fidelity is fully preserved up to 0.5 K. This result holds particular relevance for the future cointegration of spin qubits and classical control electronics.
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Affiliation(s)
| | - David J Niegemann
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, Grenoble, France
| | - Emmanuel Chanrion
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, Grenoble, France
| | - Baptiste Jadot
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, Grenoble, France
| | - Cameron Spence
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, Grenoble, France
| | | | | | | | | | | | - Romain Maurand
- Univ. Grenoble Alpes, CEA, INAC-Pheliqs, Grenoble, France
| | - Marc Sanquer
- Univ. Grenoble Alpes, CEA, INAC-Pheliqs, Grenoble, France
| | - Xavier Jehl
- Univ. Grenoble Alpes, CEA, INAC-Pheliqs, Grenoble, France
| | | | - Maud Vinet
- CEA, LETI, Minatec Campus, Grenoble, France
| | - Tristan Meunier
- Univ. Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, Grenoble, France.
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6
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Fujita T, Morimoto K, Kiyama H, Allison G, Larsson M, Ludwig A, Valentin SR, Wieck AD, Oiwa A, Tarucha S. Angular momentum transfer from photon polarization to an electron spin in a gate-defined quantum dot. Nat Commun 2019; 10:2991. [PMID: 31311919 PMCID: PMC6635371 DOI: 10.1038/s41467-019-10939-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 06/03/2019] [Indexed: 11/18/2022] Open
Abstract
Gate-defined quantum dots (QDs) are such a highly-tunable quantum system in which single spins can be electrically coupled, manipulated, and measured. However, the spins in gate-defined QDs are lacking its interface to free-space photons. Here, we verify that a circularly-polarized single photon can excite a single electron spin via the transfer of angular momentum, measured using Pauli spin blockade (PSB) in a double QD. We monitor the inter-dot charge tunneling which only occur when the photo-electron spin in one QD is anti-parallel to the electron spin in the other. This allows us to detect single photo-electrons in the spin-up/down basis using PSB. The photon polarization dependence of the excited spin state was finally confirmed for the heavy-hole exciton excitation. The angular momentum transfer observed here is a fundamental step providing a route to instant injection of spins, distributing single spin information, and possibly towards extending quantum communication. Gate-defined quantum dots offer a way to engineer electrically controllable quantum systems with potential for information processing. Here, the authors transfer angular momentum from the polarization of a single photon to the spin of a single electron in a gate-defined double quantum dot.
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Affiliation(s)
- Takafumi Fujita
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan. .,The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka, 567-0047, Japan.
| | - Kazuhiro Morimoto
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Haruki Kiyama
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.,The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka, 567-0047, Japan
| | - Giles Allison
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.,Center for Emergent Matter Science (CEMS), RIKEN, 2-1 Hirosawa, Wako-shi, Saitama, 351-0198, Japan
| | - Marcus Larsson
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
| | - Arne Ludwig
- Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, Universitätsstraße 150, Gebäude NB, D-44780, Bochum, Germany
| | - Sascha R Valentin
- Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, Universitätsstraße 150, Gebäude NB, D-44780, Bochum, Germany
| | - Andreas D Wieck
- Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, Universitätsstraße 150, Gebäude NB, D-44780, Bochum, Germany
| | - Akira Oiwa
- The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka, 567-0047, Japan.,Center for Spintronics Research Network (CSRN), Graduate School of Engineering Science, Osaka University, Osaka, 565-0871, Japan.,Quantum Information and Quantum Biology Division, Institute for Open and Transdisciplinary Research Initiatives, Osaka University, Osaka, 565-0871, Japan
| | - Seigo Tarucha
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.,Center for Emergent Matter Science (CEMS), RIKEN, 2-1 Hirosawa, Wako-shi, Saitama, 351-0198, Japan
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7
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Kurzmann A, Stegmann P, Kerski J, Schott R, Ludwig A, Wieck AD, König J, Lorke A, Geller M. Optical Detection of Single-Electron Tunneling into a Semiconductor Quantum Dot. PHYSICAL REVIEW LETTERS 2019; 122:247403. [PMID: 31322370 DOI: 10.1103/physrevlett.122.247403] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Indexed: 06/10/2023]
Abstract
The maximum information of a dynamic quantum system is given by real-time detection of every quantum event, where the ultimate challenge is a stable, sensitive detector with high bandwidth. All physical information can then be drawn from a statistical analysis of the time traces. We demonstrate here an optical detection scheme based on the time-resolved resonance fluorescence on a single quantum dot. Single-electron resolution with high signal-to-noise ratio (4σ confidence) and high bandwidth of 10 kHz make it possible to record the individual quantum events of the transport dynamics. Full counting statistics with factorial cumulants gives access to the nonequilibrium dynamics of spin relaxation of a singly charged dot (γ_{↑↓}=3 ms^{-1}), even in an equilibrium transport measurement.
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Affiliation(s)
- A Kurzmann
- Faculty of Physics and CENIDE, University of Duisburg-Essen, Lotharstrasse 1, 47057 Duisburg, Germany
- Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland
| | - P Stegmann
- Faculty of Physics and CENIDE, University of Duisburg-Essen, Lotharstrasse 1, 47057 Duisburg, Germany
| | - J Kerski
- Faculty of Physics and CENIDE, University of Duisburg-Essen, Lotharstrasse 1, 47057 Duisburg, Germany
| | - R Schott
- Chair for Applied Solid State Physics, Ruhr-Universität Bochum, Universitätsstrasse 150, 44780 Bochum, Germany
| | - A Ludwig
- Chair for Applied Solid State Physics, Ruhr-Universität Bochum, Universitätsstrasse 150, 44780 Bochum, Germany
| | - A D Wieck
- Chair for Applied Solid State Physics, Ruhr-Universität Bochum, Universitätsstrasse 150, 44780 Bochum, Germany
| | - J König
- Faculty of Physics and CENIDE, University of Duisburg-Essen, Lotharstrasse 1, 47057 Duisburg, Germany
| | - A Lorke
- Faculty of Physics and CENIDE, University of Duisburg-Essen, Lotharstrasse 1, 47057 Duisburg, Germany
| | - M Geller
- Faculty of Physics and CENIDE, University of Duisburg-Essen, Lotharstrasse 1, 47057 Duisburg, Germany
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8
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Bogan A, Studenikin S, Korkusinski M, Gaudreau L, Zawadzki P, Sachrajda AS, Tracy L, Reno J, Hargett T. Landau-Zener-Stückelberg-Majorana Interferometry of a Single Hole. PHYSICAL REVIEW LETTERS 2018; 120:207701. [PMID: 29864336 DOI: 10.1103/physrevlett.120.207701] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Indexed: 06/08/2023]
Abstract
We perform Landau-Zener-Stückelberg-Majorana (LZSM) spectroscopy on a system with strong spin-orbit interaction (SOI), realized as a single hole confined in a gated double quantum dot. Analogous to electron systems, at a magnetic field B=0 and high modulation frequencies, we observe photon-assisted tunneling between dots, which smoothly evolves into the typical LZSM funnel-shaped interference pattern as the frequency is decreased. In contrast to electrons, the SOI enables an additional, efficient spin-flip interdot tunneling channel, introducing a distinct interference pattern at finite B. Magnetotransport spectra at low-frequency LZSM driving show the two channels to be equally coherent. High-frequency LZSM driving reveals complex photon-assisted tunneling pathways, both spin conserving and spin flip, which form closed loops at critical magnetic fields. In one such loop, an arbitrary hole spin state is inverted, opening the way toward its all-electrical manipulation.
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Affiliation(s)
- Alex Bogan
- Emerging Technology Division, National Research Council, Ottawa, Canada K1A0R6
| | - Sergei Studenikin
- Emerging Technology Division, National Research Council, Ottawa, Canada K1A0R6
| | - Marek Korkusinski
- Emerging Technology Division, National Research Council, Ottawa, Canada K1A0R6
| | - Louis Gaudreau
- Emerging Technology Division, National Research Council, Ottawa, Canada K1A0R6
| | - Piotr Zawadzki
- Emerging Technology Division, National Research Council, Ottawa, Canada K1A0R6
| | - Andy S Sachrajda
- Emerging Technology Division, National Research Council, Ottawa, Canada K1A0R6
| | - Lisa Tracy
- Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
| | - John Reno
- Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
| | - Terry Hargett
- Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
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9
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Hofmann A, Maisi VF, Krähenmann T, Reichl C, Wegscheider W, Ensslin K, Ihn T. Anisotropy and Suppression of Spin-Orbit Interaction in a GaAs Double Quantum Dot. PHYSICAL REVIEW LETTERS 2017; 119:176807. [PMID: 29219432 DOI: 10.1103/physrevlett.119.176807] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Indexed: 06/07/2023]
Abstract
The spin-flip tunneling rates are measured in GaAs-based double quantum dots by time-resolved charge detection. Such processes occur in the Pauli spin blockade regime with two electrons occupying the double quantum dot. Ways are presented for tuning the spin-flip tunneling rate, which on the one hand gives access to measuring the Rashba and Dresselhaus spin-orbit coefficients. On the other hand, they make it possible to turn on and off the effect of spin-orbit interaction with a high on/off ratio. The tuning is accomplished by choosing the alignment of the tunneling direction with respect to the crystallographic axes, as well as by choosing the orientation of the external magnetic field with respect to the spin-orbit magnetic field. Spin lifetimes of 10 s are achieved at a tunneling rate close to 1 kHz.
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Affiliation(s)
- A Hofmann
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - V F Maisi
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - T Krähenmann
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - C Reichl
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - W Wegscheider
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - K Ensslin
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - T Ihn
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
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10
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Promoting Singlet/triplet Exciton Transformation in Organic Optoelectronic Molecules: Role of Excited State Transition Configuration. Sci Rep 2017; 7:6225. [PMID: 28740201 PMCID: PMC5524908 DOI: 10.1038/s41598-017-05339-4] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Accepted: 05/26/2017] [Indexed: 11/28/2022] Open
Abstract
Exciton transformation, a non-radiative process in changing the spin multiplicity of an exciton usually between singlet and triplet forms, has received much attention recently due to its crucial effects in manipulating optoelectronic properties for various applications. However, current understanding of exciton transformation mechanism does not extend far beyond a thermal equilibrium of two states with different multiplicity and it is a significant challenge to probe what exactly control the transformation between the highly active excited states. Here, based on the recent developments of three types of purely organic molecules capable of efficient spin-flipping, we perform ab initio structure/energy optimization and similarity/overlap extent analysis to theoretically explore the critical factors in controlling the transformation process of the excited states. The results suggest that the states having close energy levels and similar exciton characteristics with same transition configurations and high heteroatom participation are prone to facilitating exciton transformation. A basic guideline towards the molecular design of purely organic materials with facile exciton transformation ability is also proposed. Our discovery highlights systematically the critical importance of vertical transition configuration of excited states in promoting the singlet/triplet exciton transformation, making a key step forward in excited state tuning of purely organic optoelectronic materials.
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11
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Fujita T, Stano P, Allison G, Morimoto K, Sato Y, Larsson M, Park JH, Ludwig A, Wieck AD, Oiwa A, Tarucha S. Signatures of Hyperfine, Spin-Orbit, and Decoherence Effects in a Pauli Spin Blockade. PHYSICAL REVIEW LETTERS 2016; 117:206802. [PMID: 27886503 DOI: 10.1103/physrevlett.117.206802] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Indexed: 06/06/2023]
Abstract
We detect in real time interdot tunneling events in a weakly coupled two-electron double quantum dot in GaAs. At finite magnetic fields, we observe two characteristic tunneling times T_{d} and T_{b}, belonging to, respectively, a direct and a blocked (spin-flip-assisted) tunneling. The latter corresponds to the lifting of a Pauli spin blockade, and the tunneling times ratio η=T_{b}/T_{d} characterizes the blockade efficiency. We find pronounced changes in the behavior of η upon increasing the magnetic field, with η increasing, saturating, and increasing again. We explain this behavior as due to the crossover of the dominant blockade-lifting mechanism from the hyperfine to spin-orbit interactions and due to a change in the contribution of the charge decoherence.
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Affiliation(s)
- T Fujita
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - P Stano
- Center for Emergent Matter Science (CEMS), RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
- Institute of Physics, Slovak Academy of Sciences, 845 11 Bratislava, Slovakia
| | - G Allison
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- Center for Emergent Matter Science (CEMS), RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
| | - K Morimoto
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Y Sato
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - M Larsson
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - J-H Park
- Center for Emergent Matter Science (CEMS), RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
| | - A Ludwig
- Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, Universitätsstraße 150, Gebäude NB, D-44780 Bochum, Germany
| | - A D Wieck
- Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, Universitätsstraße 150, Gebäude NB, D-44780 Bochum, Germany
| | - A Oiwa
- The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
| | - S Tarucha
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- Center for Emergent Matter Science (CEMS), RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
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Hofmann A, Maisi VF, Gold C, Krähenmann T, Rössler C, Basset J, Märki P, Reichl C, Wegscheider W, Ensslin K, Ihn T. Measuring the Degeneracy of Discrete Energy Levels Using a GaAs/AlGaAs Quantum Dot. PHYSICAL REVIEW LETTERS 2016; 117:206803. [PMID: 27886466 DOI: 10.1103/physrevlett.117.206803] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2016] [Indexed: 06/06/2023]
Abstract
We demonstrate an experimental method for measuring quantum state degeneracies in bound state energy spectra. The technique is based on the general principle of detailed balance and the ability to perform precise and efficient measurements of energy-dependent tunneling-in and -out rates from a reservoir. The method is realized using a GaAs/AlGaAs quantum dot allowing for the detection of time-resolved single-electron tunneling with a precision enhanced by a feedback control. It is thoroughly tested by tuning orbital and spin degeneracies with electric and magnetic fields. The technique also lends itself to studying the connection between the ground-state degeneracy and the lifetime of the excited states.
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Affiliation(s)
- A Hofmann
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - V F Maisi
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - C Gold
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - T Krähenmann
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - C Rössler
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - J Basset
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - P Märki
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - C Reichl
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - W Wegscheider
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - K Ensslin
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
| | - T Ihn
- Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
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