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Superradiant Phase Transition in the Strong Coupling Regime

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arXiv 2022年

作者： Huang, Jin-Feng Tian, Lin Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan Province Department of Physics Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha410081 China School of Natural Sciences University of California MercedCA95343 United States

The Dicke model can exhibit quantum phase transition between the normal and the superradiant phases when the strength of the light-matter coupling exceeds the ultrastrong coupling regime. However, it is challenging to observe this phase transition in practical systems due to limited coupling strength or finite two-photon A2 terms. Here we show that by applying a periodic modulation to the frequency of the two-level systems in a standard Dicke model in the strong coupling regime, an anisotropic Dicke model with tunable rotating and counter-rotating terms in the ultrastrong coupling regime can be achieved. We calculate the ground state and the excitation spectrum of this model in terms of the modulation parameters. Our result shows that the superradiant phases can be observed in cavity- or circuit-quantum electrodynamics systems with strong coupling. © 2022, CC BY.

关键词： Ground state

Outstanding long-cycling lithium−sulfur batteries by core-shell structure of S@Pt composite with ultrahigh sulfur content

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Advanced Powder Materials

Advanced Powder Materials 2022年第1期1卷 88-96页

作者： Mengqin Gao Wan-Ying Zhou Yu-Xue Mo Tian Sheng Yanhong Deng Liezun Chen Kai Wang Yanliang Tan Haiqing Zhou College of Physics and Electronic Engineering Hengyang Normal UniversityHenghua Road No.16Hengyang City421002Hunan ProvinceChina College of Chemistry and Materials Science Anhui Normal UniversityWuhu241000China Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan ProvinceHunan Normal UniversityChangsha410081China Institute of Nanotechnology Karlsruhe Institute of TechnologyEggenstein-Leopoldshafen76344Germany

Here we proposed a novel approach to greatly enhance the electrochemical performance of Li-S batteries by designing a composite electrode material composed of a core-shell structure of S@Pt composite(sulfur content,85%)grown on the S *** platinum(Pt)nanosheets provide physical barrier and strong chemical binding to anchor LiPSs and improve the electronic conductivity of ***,by introducing carbon nanofibers(CNFs)as the interlayer,we achieved outstanding Li-S battery with a high initial discharge capacity of 1040 mAh g^(-1)at 1.0C and a reversible capacity of 742 mAh g^(-1)after 350 cycles,demonstrating its excellent long-term cycling stability with a low capacity decay rate of 0.08%per *** to the density functional theory(DFT)calculations,we proposed that the superior performance is attributed to the cooperative effects of the strong interfacial interaction between Pt(111)surface and the S8 molecule,and very low reaction energy of decomposition,−6.4eV.

关键词： Lithium-sulfur batteries Wet chemistry High sulfur content Pt nanoshell Carbon fibers layer

Spin Quantum Heat Engine Quantified by Quantum Steering

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Physical Review Letters 2022年第9期128卷 090602-090602页

作者： Wentao Ji Zihua Chai Mengqi Wang Yuhang Guo Xing Rong Fazhan Shi Changliang Ren Ya Wang Jiangfeng Du CAS Key Laboratory of Microscale Magnetic Resonance and School of Physical Sciences University of Science and Technology of China Hefei 230026 China CAS Center for Excellence in Quantum Information and Quantum Physics University of Science and Technology of China Hefei 230026 China Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan Province Department of Physics and Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha 410081 China

Following the rising interest in quantum information science, the extension of a heat engine to the quantum regime by exploring microscopic quantum systems has seen a boon of interest in the last decade. Although quantum coherence in the quantum system of the working medium has been investigated to play a nontrivial role, a complete understanding of the intrinsic quantum advantage of quantum heat engines remains elusive. We experimentally demonstrate that the quantum correlation between the working medium and the thermal bath is critical for the quantum advantage of a quantum Szilárd engine, where quantum coherence in the working medium is naturally excluded. By quantifying the nonclassical correlation through quantum steering, we reveal that the heat engine is quantum when the demon can truly steer the working medium. The average work obtained by taking different ways of work extraction on the working medium can be used to verify the real quantum Szilárd engine.

关键词： Quantum correlations in quantum information Quantum heat engines & refrigerators

Deterministic generation of multi-photon bundles in a quantum Rabi model

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arXiv 2022年

作者： Liu, Cheng Huang, Jin-Feng Tian, Lin Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan Province Department of Physics Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha410081 China School of Natural Sciences University of California MercedCA95343 United States

Multi-photon bundle states are crucial for a broad range of applications such as quantum metrology, quantum lithography, quantum communication, and quantum biology. Here we propose a scheme that generates multi-photon bundles via virtual excitations in a quantum Rabi model. Our approach utilizes a Ξ-type three-level atom, where the upper two levels are coupled to a cavity field to form a quantum Rabi model with ultrastrong coupling, and the transition between the lower two levels is driven by two sequences of Gaussian pulses. We show that the driving pulses induce deterministic emission of multiple photons from the eigenstates of the quantum Rabi model via the stimulated Raman adiabatic passage technique, and hence can create bundles of multiple photons on-demand in the cavity output field. We calculate the generalized second-order correlation functions of the output photons, which reveal that the emitted photons form antibunched multi-photon bundles. © 2022, CC BY.

关键词： Photons

Electrically switchable valley polarization, spin/valley filter, and valve effects in transition-metal dichalcogenide monolayers interfaced with two-dimensional ferromagnetic semiconductors

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Physical Review B 2021年第20期104卷 L201403-L201403页

作者： Ao Zhang Kaike Yang Yun Zhang Anlian Pan Mingxing Chen School of Physics and Electronics Hunan Normal University Key Laboratory for Matter Microstructure and Function of Hunan Province Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Changsha 410081 China Baoji University of Arts and Sciences Baoji 721016 China Key Laboratory for Micro-Nano Physics and Technology of Hunan Province College of Materials Science and Engineering Hunan University Changsha 410082 China

Electron valleys in transition-metal dichalcogenide monolayers drive novel physics and allow designing multifunctional architectures for applications. We propose to manipulate the electron valleys in these systems for spin/valley filter and valve devices through band engineering. Instead of the magnetic proximity effect that has been extensively used in previous studies, in our strategy, the electron valleys are directly coupled to the spin-polarized states of two-dimensional ferromagnets. We find that this coupling results in a valley-selective gap opening due to the spin-momentum locking in the transition-metal dichalcogenide monolayers. This physics gives rise to a variety of unexpected electronic properties and phenomena including half-metallicity, electrically switchable valley polarization, spin/valley filter, and valve effects in the transition-metal dichalcogenide monolayers. We further demonstrate our idea in MoTe2/CoCl2 and CoCl2/MoTe2/CoCl2 van der Waals heterojunctions based on first-principles calculations. Thus, our study provides a way of engineering the electron valleys in transition-metal dichalcogenide monolayers for contemporary devices.

关键词： First-principles calculations Valleytronics Transition metal dichalcogenides Electronic structure

Predicting hidden bottom molecular tetraquarks with a complex scaling method

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arXiv 2024年

作者： Song, Qing-Fu Lü, Qi-Fang Chen, Dian-Yong Dong, Yu-Bing Department of Physics Hunan Normal University Changsha410081 China Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Changsha410081 China Key Laboratory for Matter Microstructure and Function of Hunan Province Hunan Normal University Changsha410081 China School of Physics Southeast University Nanjing210094 China Lanzhou Center for Theoretical Physics Lanzhou University Lanzhou730000 China Institute of High Energy Physics Chinese Academy of Sciences Beijing100049 China School of Physical Sciences University of Chinese Academy of Sciences Beijing101408 China

In present work, we perform a coupled-channel analysis of B((∗s))B¯((∗s)) systems with the one-boson-exchange potentials. We first study the I(JPC) = 1(1+−) BB¯∗/B∗B¯∗ system to describe the Zb(10610) and Zb(10650) particles as molecular states and determine the reasonable range of cutoff parameter Λ. Then, other B((∗s))B¯((∗s)) combinations with different quantum numbers are systematically investigated. Some bound states and resonances appear in the isoscalar systems, while only several shallow bound states exist for isovector systems. Far away from the excited conventional P−wave bottomium, these predicted states can be easily identified as exotic particles both theoretically and experimentally. Moreover, the ηb(nS)/Υ(nS) plus light mesons are the excellent final states to search for the bound states, while the BB¯∗ + h.c. and B∗B¯∗ channels are suitable for the resonances. We highly recommend that the LHCb and Belle II Collaborations can hunt for these bottomonium-like states in future. Copyright © 2024, The Authors. All rights reserved.

关键词： Bosons

Manipulating Topological Polaritons in Optomechanical Ladders

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arXiv 2024年

作者： Wu, Jia-Kang Xu, Xun-Wei Jing, Hui Kuang, Le-Man Nori, Franco Liao, Jie-Qiao Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan Province Department of Physics Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha410081 China Institute of Interdisciplinary Studies Hunan Normal University Changsha410081 China Theoretical Quantum Physics Laboratory Cluster for Pioneering Research RIKEN Saitama Wakoshi351-0198 Japan Quantum Computing Center RIKEN Saitama Wakoshi351-0198 Japan Physics Department University of Michigan Ann ArborMI48109-1040 United States

We propose to manipulate topological polaritons in optomechanical ladders consisting of an optical Su-Schrieffer-Heeger (SSH) chain and a mechanical SSH chain connected through optomechanical (interchain) interactions. We show that the topological phase diagrams are divided into six areas by four boundaries and that there are four topological phases characterized by the Berry phases. We find that a topologically nontrivial phase of the polaritons is generated by the optomechanical interaction between the optical and mechanical SSH chains even though they are both in the topologically trivial phases. Counter-intuitively, six edge states appear in one of the topological phases with only two topological nontrivial bands, and some edge states are localized near but not at the boundaries of an open-boundary ladder. Moreover, a two-dimensional Chern insulator with higher Chern numbers is simulated by introducing proper periodical adiabatic modulations of the driving amplitude and frequency. Our work not only opens a route towards topological polaritons manipulation by optomachanical interactions, but also will exert a far-reaching influence on designing topologically protected polaritonic devices. © 2024, CC BY.

关键词： Polariton

Quantum collapse and exponential growth of out-of-time-ordered correlator in anisotropic quantum Rabi model

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arXiv 2023年

作者： Wang, Shangyun Chen, Songbai Jing, Jiliang Wang, Jieci Fan, Heng College of Physics and Electronic Engineering Hengyang Normal University Hengyang421002 China Key Laboratory of Low-Dimensional Quantum Structures Quantum Control of Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan Province Department of Physics Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha410081 China Center for Gravitation and Cosmology College of Physical Science and Technology Yangzhou University Yangzhou225009 China Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing100190 China

Quantum chaos is an intriguing topic and has attracting a great deal of interests in quantum mechanics and black hole physics. Recently, the exponential growth of out-of-time-ordered correlator (OTOC) has been proposed to diagnose quantum chaos and verify the correspondence principle. Here, we demonstrate that the exponential growth of the OTOC at early times for the initial states centered both in the chaotic and stable regions of the anisotropic quantum Rabi model. We attribute the exponential growth of the OTOC to quantum collapse which provides a novel mechanism of yielding exponential growth of the OTOC in quantum systems. Moreover, the quantum collapse effect is more obvious for the initial states centered in the chaotic one. Our results show that compared with the OTOC, the linear entanglement entropy and Loschmidt echo seem to be more effective to diagnose the signals of quantum chaos in the anisotropic quantum Rabi model. Copyright © 2023, The Authors. All rights reserved.

关键词： Quantum optics

Thermal-noise-resistant optomechanical entanglement via general dark-mode control

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arXiv 2022年

作者： Huang, Jian Lai, Deng-Gao Liao, Jie-Qiao Key Laboratory of Low-Dimensional Quantum Structures Quantum Control of Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan Province Department of Physics Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha410081 China Theoretical Quantum Physics Laboratory Riken Cluster for Pioneering Research Saitama Wako-shi351-0198 Japan

Quantum entanglement not only plays an important role in the study of the fundamentals of quantum theory, but also is considered as a crucial resource in quantum information science. The generation of macroscopic entanglement involving multiple optical and mechanical modes is a desired task in cavity optomechanics. However, the dark-mode effect is a critical obstacle against the generation of quantum entanglement in multimode optomechanical systems consisting of multiple degenerate or near-degenerate mechanical modes coupled to a common cavity mode. Here we propose an auxiliary-cavity-mode method to enhance optomechanical entanglement in a multimode optomechanical system by breaking the dark-mode effect. We find that the introduction of the auxiliary cavity mode not only assists the entanglement creation between the cavity mode and the mechanical modes, but also improves the immunity of the optomechanical entanglement to the thermal excitations by about three orders of magnitude. We also study the optomechanical entanglement in the network-coupled optomechanical system consisting of two mechanical modes and two cavity modes. By analyzing the correspondence between the optomechanical entanglement and the darkmode effect, we find that optomechanical entanglement can be largely enhanced once the dark mode is broken. In addition, we study the mechanical entanglement and find that it is negligibly small. We also present some discussions on the experimental implementation with a microwave optomechanical setup, on the relationship between the dark-mode-breaking mechanism and the center-of-mass and relative coordinates, and on the explanation of the important role of the dark-mode breaking in the enhancement of optomechanical entanglement. Our results pave the way towards the preparation of entangled optomechanical networks and noise-resistant quantum resources. Copyright © 2022, The Authors. All rights reserved.

关键词： Quantum entanglement