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Complex phase diagram and supercritical matter

Physical Review E 2024年第2期109卷 024118-024118页

作者： Xiao-Yu Ouyang Qi-Jun Ye Xin-Zheng Li State Key Laboratory for Artificial Microstructure and Mesoscopic Physics Frontier Science Center for Nano-optoelectronics and School of Physics Peking University Beijing 100871 People's Republic of China Interdisciplinary Institute of Light-Element Quantum Materials Research Center for Light-Element Advanced Materials and Collaborative Innovation Center of Quantum Matter Peking University Beijing 100871 People's Republic of China Peking University Yangtze Delta Institute of Optoelectronics Nantong Jiangsu 226010 People's Republic of China

The supercritical region is often described as uniform with no definite transitions. The distinct behaviors of the matter therein, e.g., as liquidlike and gaslike, however, suggest “supercritical boundaries.” Here we provide a mathematical description of these phenomena by revisiting the Yang-Lee theory and introducing a complex phase diagram, specifically a four-dimensional (4D) one with complex T and p. While the traditional 2D phase diagram with real temperature T and pressure p values (the physical plane) lacks Lee-Yang (LY) zeros beyond the critical point, preventing the occurrence of criticality, the off-plane zeros in this 4D scenario still induce critical anomalies in various physical properties. This relationship is evidenced by the correlation between the Widom line and LY edges in van der Waals, 2D Ising model, and water. The diverged supercritical boundaries manifest the high-dimensional feature of the phase diagram: e.g., when LY zeros of complex T or p are projected onto the physical plane, boundaries defined by isobaric heat capacity Cp or isothermal compression coefficient KT emanates. These results demonstrate the incipient phase transition nature of the supercritical matter.

关键词： Classical statistical mechanics Critical phenomena Phase diagrams Van der Waals systems Water Molecular dynamics

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Crystal-Structure Matches in Solid-Solid Phase Transitions

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Physical Review Letters 2024年第8期132卷 086101-086101页

作者： Fang-Cheng Wang Qi-Jun Ye Yu-Cheng Zhu Xin-Zheng Li State Key Laboratory for Artificial Microstructure and Mesoscopic Physics Frontier Science Center for Nano-optoelectronics School of Physics Peking University Beijing 100871 People’s Republic of China Interdisciplinary Institute of Light-Element Quantum Materials Research Center for Light-Element Advanced Materials and Collaborative Innovation Center of Quantum Matter Peking University Beijing 100871 People’s Republic of China Peking University Yangtze Delta Institute of Optoelectronics Nantong Jiangsu 226010 People’s Republic of China

The exploration of solid-solid phase transition suffers from the uncertainty of how atoms in two crystal structures match. We devised a theoretical framework to describe and classify crystal-structure matches (CSM). Such description fully exploits the translational and rotational symmetries and is independent of the choice of supercells. This is enabled by the use of the Hermite normal form, an analog of reduced echelon form for integer matrices. With its help, exhausting all CSMs is made possible, which goes beyond the conventional optimization schemes. In an example study of the martensitic transformation of steel, our enumeration algorithm finds many candidate CSMs with lower strains than known mechanisms. Two long-sought CSMs accounting for the most commonly observed Kurdjumov-Sachs orientation relationship and the Nishiyama-Wassermann orientation relationship are unveiled. Given the comprehensiveness and efficiency, our enumeration scheme provide a promising strategy for solid-solid phase transition mechanism research.

关键词： Crystal structure Martensitic phase transition Solid-solid transformations Metals Crystallography

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Self-suppressed quantum diffusion and fundamental noise limit of soliton microcombs

arXiv

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arXiv 2023年

作者： Jin, Xing Lv, Zhe Gong, Qihuang Yang, Qi-Fan State Key Laboratory for Artificial Microstructure and Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics School of Physics Peking University Beijing100871 China Collaborative Innovation Center of Extreme Optics Shanxi University Taiyuan030006 China Peking University Yangtze Delta Institute of Optoelectronics Jiangsu Nantong226010 China

Quantum diffusion of soliton microcombs has long been recognized as their fundamental noise limit. Here we surpass such limit by utilizing dispersive wave dynamics in multimode microresonators. Through the recoil force provided by these dispersive waves, the quantum diffusion can be suppressed to a much lower level that forms the ultimate fundamental noise limit of soliton microcombs. Our findings enable coherence engineering of soliton microcombs in the quantum-limited regime, providing critical guidelines for using soliton microcombs to synthesize ultralow-noise microwave and optical signals. © 2023, CC BY.

关键词： Solitons

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Quantum disorder induced by nuclear tunneling in lattice

arXiv

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arXiv 2025年

作者： Zhu, Yu-Cheng Zeng, Jia-Xi Ye, Qi-Jun Li, Xin-Zheng State Key Laboratory for Artificial Microstructure and Mesoscopic Physics Frontier Science Center for Nano-optoelectronics School of Physics Peking University Beijing100871 China Interdisciplinary Institute of Light-Element Quantum Materials Research Center for Light-Element Advanced Materials Collaborative Innovation Center of Quantum Materials Peking University Beijing100871 China Peking University Yangtze Delta Institute of Optoelectronics Jiangsu Nantong226010 China

Lattice degrees of freedom (DoFs) may induce quantum disorder (QD) when nuclear tunneling outvies long-range order, but conventional phonon theory is incapable of describing such QD phases. Here we develop a method based on path-integral molecular dynamics to solve this problem. Its accuracy is verified in a double-well chain model and it is applied to a real material from first principles. A quantum order-disorder-order phase transition sequence is demonstrated when varying the strength of quantum fluctuations using the lattice constants as the tuning factor. Combining the excitation spectra and Rényi entanglement entropy, we pinpoint the QD region. This picture may be general in lattice systems having soft phonon modes, not limited to quantum paraelectricity, in which novel entangled lattice motion and its coupling with other DoFs can be expected. © 2025, CC BY.

关键词： Degrees of freedom (mechanics)

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Effect of Grain Coalescence on Dislocation and Stress Evolution of GaN Films Grown on Nanoscale Patterned Sapphire Substrates

arXiv

引用

arXiv 2023年

作者： Pan, Zuojian Chen, Zhizhong Chen, Yiyong Zhang, Haodong Yang, Han Nie, Jingxin Deng, Chuhan Dong, Boyan Wang, Daqi Li, Yuchen Chen, Weihua Jiao, Fei Kang, Xiangning Jia, Chuanyu Liang, Zhiwen Wang, Qi Zhang, Guoyi Shen, Bo State Key Laboratory for Artificial Microstructure and Mesoscopic Physics School of Physics Peking University Beijing100871 China Dongguan Institute of Optoelectronics Peking University Guangdong Dongguan523808 China Yangtze Delta Institute of Optoelectronics Peking University Jiangsu Nantong226000 China State Key Laboratory of Nuclear Physics and Technology School of Physics Peking University Beijing100871 China School of Electrical Engineering and Intelligentization Dongguan University of Technology Dongguan523808 China

Two types of nucleation layers (NLs), including in-situ low-temperature grown GaN (LT-GaN) and ex-situ sputtered physical vapor deposition AlN (PVD-AlN), are applied on cone-shaped nanoscale patterned sapphire substrate (NPSS). The initial growth process of GaN on these two NLs is comparably investigated by a series of growth interruptions. The coalescence process of GaN grains is modulated by adjusting the three-dimensional (3D) temperatures. The results indicate that higher 3D temperatures reduce the edge dislocation density while increasing the residual compressive stress in GaN films. Compared to the LT-GaN NLs, the PVD-AlN NLs effectively resist Ostwald ripening and facilitate the uniform growth of GaN grains on NPSS. Furthermore, GaN films grown on NPSS with PVD-AlN NLs exhibit a reduction of over 50% in both screw and edge dislocation densities compared to those grown on LT-GaN NLs. Additionally, PVD-AlN NLs result in an increase of about 0.5 GPa in the residual compressive stress observed in GaN films. © 2023, CC BY.

关键词： Physical vapor deposition

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Tunable spin photogalvanic effect in two-dimensional van der Waals ferroelectric semiconductors with spin-orbit coupling

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Physical Review B 2024年第19期109卷 195202-195202页

作者： Shibo Fang Min Wang Xingyue Yang Zongmeng Yang Qiuhui Li Zhaochu Luo Jing Lu State Key Laboratory of Artificial Microstructure and Mesoscopic Physics School of Physics Peking University Beijing 100871 People's Republic of China School of Information Science and Engineering Hebei University of Science and Technology Shijiazhuang 050018 People's Republic of China Collaborative Innovation Center of Quantum Matter Beijing 100871 People's Republic of China Beijing Key Laboratory for Magnetoelectric Materials and Devices (BKL-MEMD) Peking University Beijing 100871 People's Republic of China Peking University Yangtze Delta Institute of Optoelectronics Nantong 226010 People's Republic of China Key Laboratory for the Physics and Chemistry of Nanodevices Peking University Beijing 100871 People's Republic of China Beijing Key Laboratory of Quantum Devices Peking University Beijing 100871 People's Republic of China

Spin photogalvanic effect is a nonlinear effect that can generate spin currents through optical excitation in intrinsic semiconductors without parity inversion symmetry. The efficient control of the spin photogalvanic effect is of great significance for the research of computing-in-memory devices. In this work, we investigate the ferroelectric modulation of the spin photogalvanic effect in two-dimensional (2D) van der Waals (vdW) ferroelectric semiconductors with spin-orbit coupling, including the in-plane, out-of-plane, and in-plane/out-of-plane-coupled ferroelectrics. We provide the general form of the spin photogalvanic effect controlled by ferroelectricity in 2D vdW spin-orbit coupling ferroelectric semiconductors by the second-order perturbation theory. In the in-plane ferroelectrics excited by circularly polarized light, we discover an effect where the reversal of the ferroelectric polarization will maintain the spin current unchanged but change the direction of the charge current. We name this effect the hidden spin current modulation. Using first-principles quantum transport simulation, we validate our theory with three cases of the black phosphorus-like Bi (in-plane ferroelectric), monolayer α-GeTe (out-of-plane ferroelectric), and α−In2Se3 (in-plane and out-of-plane coupled ferroelectric). Our study paves the way for the research of next-generation low-dimensional computing-in-memory devices.

关键词： Photocurrent Photogalvanic effect Spin current Ferroelectrics Van der Waals systems Density functional theory Landauer formula

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Facile and fast growth of high mobility nanoribbons of ZrTe5

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Chinese physics B 2020年第6期29卷 69-74页

作者： Jingyue Wang Jingjing Niu Xinqi Li Xiumei Ma Yuan Yao Xiaosong Wu State Key Laboratory for Artificial Microstructure and Mesoscopic Physics Peking UniversityBeijing 100871China Institute of Physics Chinese Academy of SciencesBeijing 100190China Frontiers Science Center for Nano-optoelectronics and Collaborative Innovation Center of Quantum Matter Peking UniversityBeijing 100871China Department of Physics South University of Science and Technology of ChinaShenzhen 518055China

Recently, ZrTe5 has received a lot of attention as it exhibits various topological phases, such as weak and strong topological insulators, a Dirac semimetal, a three-dimensional quantum Hall state, and a quantum spin Hall insulator in the monolayer limit. While most of studies have been focused on the three-dimensional bulk material, it is highly desired to obtain nanostructured materials due to their advantages in device applications. We report the synthesis and characterizations of ZrTe5 nanoribbons. Via a silicon-assisted chemical vapor transport method, long nanoribbons with thickness as thin as 20 nm can be grown. The growth rate is over an order of magnitude faster than the previous method for the bulk ***, transport studies show that the nanoribbons are of low unintentional doping and high carrier mobility, over30000 cm2/V·s, which enable reliable determination of the Berry phase of π in the ac plane from quantum oscillations. Our method holds great potential in growth of high quality ultra-thin nanostructures of ZrTe5.

关键词： ZrTe5 nanoribbons growth chemical vapor transport mobility

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Functionalized Porphyrin as a Carrier Bridge and a Passivator for Perovskite Solar Cells

SSRN

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SSRN 2024年

作者： Tao, Longchen Zhang, Haitao Zhu, Xinyu Qi, Chenhan Ye, Tianhong Chen, Niping Xiao, Lixin Li, Baojun Sun, Xufei Yun, Daqin Zheng, Lingling College of Energy Xiamen University Xiang’an Campus Fujian Xiamen361100 China Department of Physics Xiamen University Fujian Xiamen361005 China Jiujiang Research Institute Xiamen University Jiujiang332000 China State Key Laboratory of Artificial Microstructure and Mesoscopic Physics School of Physics Peking University Beijing100871 China Fujian Key Laboratory of Architectural Coating Skshu Paint Co. Ltd. Fujian Putian351100 China Co. Ltd. Shanghai201100 China

Interfacial modification becomes one of the most emerging strategies in the state-of-the-art perovskite solar cells (PSCs). Here, two porphyrin derivatives (p-MeOTPP, m-DMeOTPP) with different numbers of methoxy groups are employed as the modifiers between perovskite and the hole transporting layer (HTL). The interaction at both of perovskite/modifier and modifier/HTL interfaces, and the hole-transfer property of the modifier itself are comprehensively studied, which are jointly responsible for the significant improvement in the electrical properties of the device. More importantly, discussion on a molecular level reveals the distinct roles of modifiers with highly similar structures. A highest power conversion efficiency (PCE) of 24.56% is achieved for m-DMeOTPP modified PSCs, which is attributed to a synergy of efficient passivation effect at perovskite/modifier interface, sufficient built-in potential at modifier/HTL interface and minimal reorganization energy for hole hopping process. p-MeOTPP has a stronger passivation ability, but causes unfavorable interfacial dipole at modifier/HTL interface and a large energy barrier when hole’s hopping, only resulting in a smaller enhancement in PCE. This work presents a synergy mechanism for interfacial engineering to pursue PSCs with high efficiency and stability, and provides practical guidelines at molecular level to design a modifier not only as an efficient passivator but also as a high-speed carrier bridge. © 2024, The Authors. All rights reserved.

关键词： Perovskite solar cells

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Spin texture and tunneling magnetoresistance in atomically thin CrSBr

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Physical Review B 2025年第14期111卷 L140417-L140417页

作者： Ziqi Liu Yichang Sun Chengfeng Zhu Canyu Hong Yuchen Gao Zeyuan Sun Kenji Watanabe Takashi Taniguchi Shiwei Wu Zuxin Chen Pingfan Gu Yu Ye State Key Laboratory for Artificial Microstructure & Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics School of Physics Peking University Beijing 100871 China State Key Laboratory of Surface Physics Key Laboratory of Micro and Nano Photonic Structures (MOE) and Department of Physics Fudan University Shanghai 200433 China Research Center for Electronic and Optical Materials National Institute for Materials Science 1-1 Namiki Tsukuba 305-0044 Japan Research Center for Materials Nanoarchitectonics National Institute for Materials Science 1-1 Namiki Tsukuba 304-0044 Japan School of Semiconductor Science and Technology South China Normal University Foshan 528225 China MIIT Key Laboratory of Semiconductor Microstructure and Quantum Sensing Department of Applied Physics Nanjing University of Science and Technology Nanjing 210094 China Collaborative Innovation Center of Quantum Matter Beijing 100871 China Liaoning Academy of Materials Shenyang 110167 China

The exploration of spin configurations and magnetoresistance in van der Waals magnetic semiconductors, particularly in the realm of thin-layer structures, is of paramount significance for the development of two-dimensional spintronic nanodevices. In this Letter, we present detailed magnetotransport and photoluminescence studies on few-layer CrSBr flakes utilizing a vertical tunneling device configuration. Our investigations revealed complex magnetic states along the evolutionary path of few-layer CrSBr. We observed intermediate states exhibiting identical net magnetization demonstrate rectification properties, reminiscent of a diodelike behavior at positive and negative bias voltages. Notably, in devices with five-layer CrSBr, we detected an intriguing positive magnetoresistive state when subjected to an in-plane magnetic field along the b axis. The implementation of the Mott two-current model successfully calculated the tunneling resistance of different magnetic states, thereby elucidating the spin configurations responsible for the observed transport phenomena. These insights not only provide different perspectives on the intricate spin textures of two-dimensional CrSBr, but also highlight the efficacy of tunneling measurements as a sensitive method for probing magnetic order in van der Waals materials.

关键词： Van der Waals forces

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Defect suppression and energy level alignment in formamidinium-based perovskite solar cells

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Journal of Energy Chemistry 2022年第4期31卷 65-72页

作者： Yi Wang Xiaobing Wang Chenhui Wang Renying Cheng Lanxin Zhao Xu Wang Xuewen Zhang Jingzhi Shang Huang Zhang Lichen Zhao Yongguang Tu Wei Huang Frontiers Science Center for Flexible Electronics Xi’an Institute of Flexible Electronics(IFE)&Xi’an Institute of Biomedical Materials and EngineeringNorthwestern Polytechnical UniversityXi’an 710072ShaanxiChina Engineering Research Centre of Environment-Friendly Functional Materials Ministry of EducationFujian Engineering Research Centre of Green Functional MaterialsHuaqiao UniversityXiamen 361021FujianChina Honors College Northwestern Polytechnical UniversityXi’an 710072ShaanxiChina State Key Laboratory for Artificial Microstructure and Mesoscopic Physics School of PhysicsFrontiers Science Center for Nano-optoelectronics&Collaborative Innovation Center of Quantum MatterPeking UniversityBeijing 100871China Key Laboratory of Flexible Electronics(KLoFE)&Institution of Advanced Materials(IAM) Jiangsu National Synergetic Innovation Center for Advanced Materials(SICAM)Nanjing Tech UniversityNanjing 211816JiangsuChina Key Laboratory for Organic Electronics&Information Displays(KLOEID)&Institute of Advanced Materials(IAM) Nanjing University of Posts and TelecommunicationsNanjing 210023JiangsuChina

The vast majority of high-performance perovskite solar cells(PSCs) are based on a formamidinium lead iodide(FAPbI_(3))-dominant composition. Nevertheless, the FA-based perovskite films suffer from undesirable phase transition and defects-induced non-ideal interfacial recombination, which significantly induces energy loss and hinders the improvement of device performance. Herein, we employed 4-fluorophenylmethylammonium iodide(F-PMAI) to modulate surface structure and energy level alignment of the FA-based perovskite films. The superior optoelectronic films were obtained with reduced trap density, pure α-phase FAPbI_(3) and favorable energy band bending. The lifetime of photogenerated charge carriers increased from 489.3 ns to 1010.6 ns, and a more “p-type” perovskite film was obtained by the post-treatment with F-PMAI. Following this strategy, we demonstrated an improved power conversion efficiency of 22.59% for the FA-based PSCs with an open-circuit voltage loss of 399 m V.

关键词： Perovskite solar cells Defect suppression Energy level alignment Phase transition 4-Fluorophenylmethylammonium iodide

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