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Producing keV photoelectrons from one-dimensional stretched H+2 by near-infrared intense chirped laser fields

Optics Express 2025年第9期33卷 19760-19770页

作者： Wang, Na Jing, Wen-Quan Du, Jin-Xu Jiao, Zhi-Hong Wang, Guo-Li Zhao, Song-Feng Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province College of Physics and Electronic Engineering Northwest Normal University Lanzhou730070 China Hunan Key Laboratory of Super-Microstructure and Ultrafast Process School of Physics Central South University Changsha410083 China

We theoretically present a method for producing keV high-order above-threshold ionization (HATI) electrons from one-dimensional stretched H+2 in near-infrared (NIR) intense chirped laser fields by solving the time-dependent Schrödinger equation in momentum space. We find that the photoelectron energy can only be extended to 18Up if the stretched H+2 is driven by a chirp-free laser pulse, with Up being the ponderomotive energy. However, the cutoff position of the HATI plateau sensitively depends on the chirp rate, intensity and wavelength of laser pulses and the highest photoelectron energy can reach up to 46Up (i.e., 2.577 keV) when the stretched H+2 is exposed to NIR intense chirped laser fields. Based on the classical analysis method, we confirm that the dramatic extension of photoelectron energy can be attributed to the well-known fact that the released electron from one proton (i.e., A or B) is elastically scattered by the neighboring proton (i.e., B or A). This work demonstrates the possibility for producing keV photoelectrons using table-top NIR intense chirped laser fields. © 2025 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.

关键词： Schrodinger equation

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Frustration-enhanced persistent currents in correlated trimer nanorings

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Physical Review B 2025年第8期111卷 L081117-L081117页

作者： Tie-Feng Fang Wei-Tao Lu Ai-Min Guo Qing-Feng Sun School of Physical Science and Technology Nantong University Nantong 226019 China Hunan Key Laboratory for Super-microstructure and Ultrafast Process School of Physics and Electronics Central South University Changsha 410083 China International Center for Quantum Materials School of Physics Peking University Beijing 100871 China Hefei National Laboratory Hefei 230088 China

We investigate the persistent current in a correlated trimer nanoring comprising three magnetic atoms, which sits on a metallic host and encloses a magnetic flux. In the molecular-orbital regime, charge fluctuations can reverse the aromaticity of the trimer molecule by driving quantum phase transitions between many-body states. It is shown that in frustrated trimers the superexchange-induced current as a function of interatom hopping is enhanced by the competition of conflicting magnetic orders, with an asymmetric peak at the quantum criticality separating the ferromagnetic and antiferromagnetic Kondo regimes. Interestingly, the critical current undergoes an anomalous rise with temperature before decaying, signaling the suppression of the Kondo bound state at finite temperature. Our results demonstrate that the coherent current response to external flux indeed conveys important information on the states of strongly correlated systems.

关键词： Nanorings

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Channel-resolved photoionization time delay of hydrogen atoms in two-color ultraviolet laser fields

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Optics Express 2025年第7期33卷 15044-15056页

作者： Gao, Xuan-Hong Jing, Wen-Quan Du, Jin-Xu Jiao, Zhi-Hong Wang, Guo-Li Zhao, Song-Feng College of Physics and Electronic Engineering Northwest Normal University Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province Lanzhou730070 China Laboratory of Super-Microstructure and Ultrafast Process School of Physics Central South University Changsha410083 China

We investigate theoretically the phase-dependent photoelectron spectra in resonance-enhanced multiphoton ionization (REMPI) of hydrogen atoms with 200-400-nm ultraviolet laser fields by solving the time-dependent Schrödinger equation. Unlike photoionization time delay in the REMPI of Ne and Ar driven by 400-800-nm laser fields, several Rydberg states are involved [Phys. Rev. A 98, 013409 (2018);Phys. Rev. A 109, 013103 (2024)]. Here we show that the electron can be released to the continuum state by absorbing three 200-nm photons (i.e., non-resonant channel) or firstly excited to one Rydberg state (i.e., the 3d state) through a two-photon transition and then removed by absorbing another 200-nm photon (i.e., resonant channel). The channel-resolved time delays of the above-threshold ionization (ATI) and sideband (SB) peaks are extracted from the phase-dependent photoelectron spectra. We find that a relative time delay about +165 attoseconds exists between the first resonant SB and non-resonant SB. The phase shifts of the high-energy electrons in these two channels are affected by the continuum-continuum (CC) transitions and the centrifugal barrier effect. Additionally, the intensities of the pump and probe fields affect the phase shifts of high-energy electrons in the non-resonant and resonant channels, respectively. This study demonstrates the possibility of higher-order transitions in ATI of hydrogen atoms at higher laser intensities and offers a theoretical insight for understanding the channel-resolved time delays in atomic REMPI processes. © 2025 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement.

关键词： Rydberg states

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Giant magnetocaloric effect in Cr-based two-dimensional materials

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Applied Physics Letters 2025年第17期126卷

作者： Zhai, Guangwei Xu, Xiong Niu, Chang Xie, Weifeng Li, Min Lin, Xuhui Wang, Hui School of Physics Hunan Key Laboratory of Super Microstructure and Ultrafast Process Hunan Key Laboratory of Nanophotonics and Devices State Key Laboratory of Powder Metallurgy Central South University Changsha410083 China

The rise of two-dimensional magnets offers a broad research platform for exploring low-dimensional magnetocaloric technology for efficient and green refrigeration applications. Here, we focus on a two-dimensional ferromagnetic semiconductor CrSX (X = F, Cl, Br, I) to investigate its magnetocaloric properties and thermal transport properties along with the underlying physical mechanisms. It is found that CrSX intrinsically possesses a substantial isothermal entropy change ( − Δ S mag max ) of 12.3 μJ m−2 K−1 and adiabatic temperature change ( Δ T a d max ) of 2.3 K during magnetic phase transition. Surprisingly, it exhibits remarkably high thermal conductivity of up to 54.47 W/mK that is attributed to the extended phonon lifetime. Additionally, tensile strain effectively modulates the Curie temperature and refrigerant capacity, with tensile strain weakening direct antiferromagnetic coupling, thus enhancing ferromagnetism. Hole doping efficiently adjusts the magnetic exchange interaction, which enhances the Curie temperature of CrSI to room temperature (305 K) while maintaining a high refrigerant capacity of 180 J/mol under a magnetic field, ascribing to the reduced energy gap between eg orbitals of transition metal cations and p orbitals of nonmagnetic anions. The present work provides insights for understanding the relation between magnetic exchange interactions, thermal transport, and refrigerant performance, offering guidance for designing two-dimensional magnets for magnetocaloric applications. © 2025 Author(s).

关键词： Magnetic refrigeration

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Precise quantum control of molecular rotation toward a desired orientation

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Physical Review Research 2025年第1期7卷 L012049-L012049页

作者： Qian-Qian Hong Daoyi Dong Niels E. Henriksen Franco Nori Jun He Chuan-Cun Shu Hunan Key Laboratory of Nanophotonics and Devices Hunan Key Laboratory of Super-Microstructure and Ultrafast Process School of Physics Central South University Changsha 410083 China Australian Artificial Intelligence Institute Faculty of Engineering and Information Technology University of Technology Sydney NSW 2007 Australia Department of Chemistry Technical University of Denmark Building 207 DK-2800 Kongens Lyngby Denmark Quantum Computing Center and Theoretical Quantum Physics Laboratory RIKEN Saitama 351-0198 Japan Physics Department University of Michigan Ann Arbor Michigan 48109 USA

The lack of a direct map between control fields and desired control objectives poses a significant challenge in applying quantum control theory to quantum technologies. Here, we propose an analytical framework to precisely control a limited set of quantum states and construct desired coherent superpositions using a well-designed laser pulse sequence with optimal amplitudes, phases, and delays. This theoretical framework that corresponds to a multilevel pulse-area theorem establishes a straightforward mapping between the control parameters of the pulse sequence and the amplitudes and phases of rotational states within a specific subspace. As an example, we utilize this approach to generate 15 distinct and desired rotational superpositions of ultracold polar molecules, leading to 15 desired field-free molecular orientations. By optimizing the superposition of the lowest 16 rotational states, we demonstrate that this approach can achieve a maximum orientation value of |〈cosθ〉|max above 0.99, which is very close to the global optimal value of 1 that could be achieved in an infinite-dimensional state space. This work marks a significant advancement in achieving precise control over multilevel subsystems within molecules. It holds potential applications in molecular alignment and orientation, as well as in various interdisciplinary fields related to the precise quantum control of ultracold polar molecules, opening up considerable opportunities in molecular-based quantum techniques.

关键词： Molecular orientation

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Maximizing orientation of a three-state molecule in a cavity with analytically designed pulses

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Physical Review A 2025年第3期111卷 033119-033119页

作者： Li-Bao Fan Hai-Ji Li Qi Chen Hang Zhou Heng Liu Chuan-Cun Shu Hunan Key Laboratory of Nanophotonics and Devices Hunan Key Laboratory of Super-Microstructure and Ultrafast Process School of Physics Central South University Changsha 410083 China Hunan Provincial Key Laboratory of Flexible Electronic Materials Genome Engineering School of Physics and Electronic Science Changsha University of Science and Technology Changsha 410114 China

We theoretically explore the precise control of a molecular polariton by strongly coupling the lowest three rotational states of a single molecule with a single-mode cavity. We examine two distinct cavity resonance configurations: a fundamental frequency cavity (ωc=2B with the rotational constant B) resonating with the lowest two rotational states, and a second harmonic cavity (ωc=4B) coupling with the first and second excited rotational states. We propose two control schemes based on the two polariton configurations and derive the corresponding pulse-area theorems to achieve a theoretical maximum orientation of 0.7746, identical to the molecule without the cavity. The control schemes are analyzed in carbonyl sulfide (OCS) molecules in their ground rotational state. Our numerical simulation results demonstrate the theoretical control schemes and analyze the sensitivity of the molecular polariton orientation degree to the control field bandwidth and phases. This work provides a valuable reference for achieving maximum field-free orientation of ultracold three-state molecules in a cavity using analytically designed pulses.

关键词： Molecular polarity

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Piezovalley effect and magnetovalley coupling in altermagnetic semiconductors studied by first-principles calculations

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Physical Review B 2025年第13期111卷 134429-134429页

作者： Weifeng Xie Xiong Xu Yunliang Yue Huayan Xia Hui Wang School of Microelectronics and Physics Hunan University of Technology and Business Changsha 410205 China School of Physics Hunan Key Laboratory of Super Microstructure and Ultrafast Process Hunan Key Laboratory of Nanophotonics and Devices State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China College of Information Engineering Yangzhou University Yangzhou 225127 China

Clarifying the physical origin of valley polarization and exploring promising ferrovalley materials are conducive to the application of valley degrees of freedom in the field of information storage. Here, we explore two altermagnetic semiconductors (monolayers Nb2Se2O and Nb2SeTeO) with Néel temperature above room temperature based on first-principles calculations. We find that uniaxial strain induces valley polarization without spin-orbital coupling (SOC) in altermagnets owing to the piezovalley effect, while uniaxial compressive strain transforms the intrinsic ferrovalley semiconductor into a semimetal, half metal, and metal. Moreover, moderate biaxial compressive strain renders Janus monolayer Nb2SeTeO to robust Dirac-conelike band dispersion. The SOC and intrinsic in-plane magnetocrystalline anisotropy energy induce Dirac-conelike altermagnets to generate apparent valley polarization through magnetovalley coupling. In terms of SOC perturbation, we elucidate the physical mechanism behind in-plane magnetization-induced valley polarization and demonstrate that valley polarization is negatively correlated with the band gap. The present work reveals the physical origin of valley polarization in altermagnets and expands the application of ferrovalley at room temperature in valleytronics.

关键词： Degrees of freedom (mechanics)

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Dual-Interface Passivation of Wide-Bandgap Perovskite Films for Efficient Four-Terminal Perovskite-Organic Tandem Solar Cells

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Journal of Physical Chemistry Letters 2025年 5195-5201页

作者： Aslam, Fawad Li, Hengyue Chang, Jianhui Tahir, Muhammad Zahid, Muhammad Sadiq, Muhammad Irfan Liao, Xiang Zeng, Qiang Liu, Fangyang Yang, Junliang Hunan Key Laboratory for Super-microstructure and Ultrafast Process School of Physics Central South University Changsha 410083 China Hunan Key Laboratory of Nanophotonics and Devices School of Physics Central South University Hunan Changsha 410083 China School of Metallurgy and Environment Central South University Changsha 410083 China State Key Laboratory of Powder Metallurgy Central South University Hunan Changsha 410083 China

Interface defects in perovskite solar cells (PSCs) can significantly impair device efficiency by promoting nonradiative recombination, hindering charge transport, and facilitating ion migration. In this work, we introduce a dual-interface passivation strategy utilizing 2-(N-morpholino)ethanesulfonic acid potassium (MESK) and octylammonium iodide (OAI), targeting both the electron transport layer (ETL)/perovskite and perovskite/hole transport layer (HTL) interfaces to enhance the efficiency of wide-bandgap PSCs based on FA_0.8Cs_0.2Pb(I_0.6Br_0.4)₃ with a bandgap of 1.77 eV. The sulfonic group in MESK passivates bottom interface defects through coordination with Pb ions, while the amine group in OAI interacts with Pb and halide ions to effectively passivate top interface defects. The dual-interface passivation strategy improves perovskite crystallinity, enlarges grain size, and reduces nonradiative recombination. As a result, the performance of PSCs is significantly enhanced, achieving a power conversion efficiency (PCE) of 23.69% in a four-terminal (4T) perovskite-organic tandem solar cell (TSC), which provides a promising and sustainable solution for the commercialization of TSCs. © 2025 American Chemical Society.

关键词： Bromine compounds

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Dynamical theory of chiral-induced spin selectivity in electron donor–chiral molecule–acceptor systems

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Physical Review B 2025年第20期111卷 205417-205417页

作者： Tian-Yi Zhang Yue Mao Ai-Min Guo Qing-Feng Sun International Center for Quantum Materials School of Physics Peking University Beijing 100871 China Hunan Key Laboratory for Super-microstructure and Ultrafast Process School of Physics Central South University Changsha 410083 China Hefei National Laboratory Hefei 230088 China

The chiral-induced spin selectivity (CISS) effect, a phenomenon where the chirality of molecules imparts significant spin selectivity to electron transfer processes, has garnered increasing interest among the chemistry, biology, and physics communities. Although this effect was discovered more than a decade ago, the dynamical process of how electron spin polarization is caused by chiral molecules is still unclear. Here, we propose a dynamical theory of electron transfer in donor-chiral molecule bridge-acceptor systems without electrodes or substrates based on the Lindblad-type master equation. We demonstrate that the molecular spin-orbit coupling generates unequal spin velocities and achieves steady spin polarization with the help of dephasing. Our work elucidates the dynamical process of CISS and may promote the applications of chiral-based spintronic devices.

关键词： Spin orbit coupling

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A passive power management unit based on charge shunting and current enhancing for significantly improving the efficiency of triboelectric energy harvesting

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Nano Energy 2025年 141卷

作者： Xu, Xiaowen Bian, Zhaolong Luo, Yuguang Xiongsong, Tengxiao Zhang, Hao Gao, Mang Dai, Guozhang Yang, Junliang School of Electronic Information Central South University Hunan Changsha410083 China Hunan Key Laboratory of Nanophotonics and Devices School of Physics Central South University Hunan Changsha410083 China Hunan Key Laboratory for Super-Microstructure and Ultrafast Process School of Physics Central South University Changsha410083 China

The power management unit (PMU) plays a crucial role in enhancing the energy storage efficiency of triboelectric nanogenerators (TENGs). However, the majority of traditional PMUs cannot meet the high requirements of modern Internet of Things (IoT) for power management systems due to the limitation in achieving fully self-powered functions or relatively high energy storage efficiency. In this work, we propose a fully self-powered PMU that combines charge-shunting and current-enhancing strategies to significantly improve energy storage efficiency. The charge-shunting circuit effectively mitigates energy losses caused by charge recombination, while the current-enhancing circuit significantly boosts the output current compared to conventional designs. Moreover, the proposed PMU achieves the energy storage efficiency of 53.6 %, representing a significant improvement over conventional passive electronic switch PMUs. This PMU enables continuous wireless transmission of attitude sensor data via Bluetooth for one min. This work presents a self-powered PMU for TENGs, offering a practical solution for widely used IoT sensor networks. © 2025 Elsevier Ltd

关键词： Electric energy storage

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