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Quantum parametric oscillator heat engines in squeezed thermal baths: Foundational theoretical issues

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arXiv 2021年

作者： Arisoy, Onat Hsiang, Jen-Tsung Hu, Bei-Lok Chemical Physics Program Institute for Physical Science and Technology University of Maryland College ParkMD20742 United States Center for High Energy and High Field Physics National Central University Chungli32001 Taiwan Joint Quantum Institute Maryland Center for Fundamental Physics University of Maryland College ParkMD20742 United States

In this paper we examine some foundational issues of a class of quantum engines where the system consists of a single quantum parametric oscillator, operating in an Otto cycle consisting of 4 stages of two alternating phases: the isentropic phase is detached from any bath (thus a closed system) where the natural frequency of the oscillator is changed from one value to another, and the isothermal phase where the system (now rendered open) is put in contact with one or two squeezed baths of different temperatures, whose nonequilibrium dynamics follows the Hu-Paz-Zhang (HPZ) master equation for quantum Brownian motion. The HPZ equation is an exact nonMarkovian equation which preserves the positivity of the density operator and is valid for a) all temperatures, b) arbitrary spectral density of the bath, and c) arbitrary coupling strength between the system and the bath. Taking advantage of these properties we examine some key foundational issues of theories of quantum open and squeezed systems for these two phases of the quantum Otto engines. This include, i) the nonMarkovian regimes for non-Ohmic, low temperature baths, ii) what to expect in nonadiabatic frequency modulations, iii) strong system-bath coupling, as well as iv) the proper junction conditions between these two phases. Our aim here is not to present ways for attaining higher efficiency but to build a more solid theoretical foundation for quantum engines of continuous variables covering a broader range of parameter spaces hopefully of use for exploring such possibilities. Copyright © 2021, The Authors. All rights reserved.

关键词： Spectral density

Hyperbolic phonon-polariton electroluminescence in graphene-hBN van der Waals heterostructures

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arXiv 2023年

作者： Guo, Qiushi Esin, Iliya Li, Cheng Chen, Chen Liu, Song Edgar, James H. Zhou, Selina Demler, Eugene Refael, Gil Xia, Fengnian Department of Electrical Engineering Yale University New Haven06511 United States Photonics Initiative Advanced Science Research Center City University of New York NY United States Physics Program Graduate Center City University of New York New YorkNY United States Department of Physics Institute for Quantum Information and Matter California Institute of Technology PasadenaCA91125 United States Tim Taylor Department of Chemical Engineering Kansas State University ManhattanKS66506 United States Department of Electrical Engineering California Institute of Technology PasadenaCA91125 United States Institute for Theoretical Physics ETH Zurich Zürich Switzerland

Phonon-polaritons are electromagnetic waves resulting from the coherent coupling of photons with optical phonons in polar dielectrics. Due to their exceptional ability to confine electric fields to deep subwavelength scales with low loss, they are uniquely poised to enable a suite of applications beyond the reach of conventional photonics, such as sub-diffraction imaging and near-field energy transfer. The conventional approach to exciting phonon-polaritons through optical methods, however, necessitates costly mid-infrared and terahertz coherent light sources along with near-field scanning probes, and generally leads to low excitation efficiency due to the substantial momentum mismatch between phonon-polaritons and free-space photons. Here, we demonstrate that under proper conditions, phonon-polaritons can be excited all-electrically by flowing charge carriers. Specifically, in hexagonal boron nitride (hBN)/graphene heterostructures, by electrically driving charge carriers in ultra-high-mobility graphene out of equilibrium, we observe bright electroluminescence of hBN’s hyperbolic phonon-polaritons (HPhPs) at mid-IR frequencies. The HPhP electroluminescence shows a temperature and carrier density dependence distinct from black-body or super-Planckian thermal emission. Moreover, the carrier density dependence of HPhP electroluminescence spectra reveals that HPhP electroluminescence can arise from both inter-band transition and intra-band Cherenkov radiation of charge carriers in graphene. The HPhP electroluminescence offers fundamentally new avenues for realizing electrically-pumped, tunable mid-IR and THz phonon-polariton lasers, and efficient cooling of electronic devices. © 2023, CC BY.

关键词： Photons

Proton-mediated reversible switching of metastable ferroelectric phases with low operation voltages

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arXiv 2023年

作者： He, Xin Ma, Yinchang Zhang, Chenhui Fu, Aiping Hu, Weijin Xu, Yang Yu, Bin Liu, Kai Wang, Hua Zhang, Xixiang Xue, Fei ZJU-Hangzhou Global Scientific and Technological Innovation Center School of Micro-Nano Electronics Zhejiang University Hangzhou310020 China Physical Science and Engineering Division King Abdullah University of Science and Technology Thuwal23955-6900 Saudi Arabia College of Chemistry and Chemical Engineering Qingdao University Qingdao266071 China Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang110016 China School of Materials Science and Engineering University of Science and Technology of China Shenyang110016 China Physics Department Georgetown University WashingtonDC20057 United States

The exploration of ferroelectric phase transitions enables an in-depth understanding of ferroelectric switching and promising applications in information storage. However, controllably tuning the dynamics of ferroelectric phase transitions remains challenging owing to inaccessible hidden phases. Here, using protonic gating technology, we create a series of metastable ferroelectric phases and demonstrate their reversible transitions in van der Waals ferroelectric α-In2Se3 transistors. By varying the gate bias, protons can be incrementally injected or extracted, achieving controllable tuning of the ferroelectric α-In2Se3 protonic dynamics across the channel and obtaining numerous intermediate phases. Combining piezoelectric force microscopy and electrical hysteresis measurements, we surprisingly discover that the gate tuning of α-In2Se3 protonation is volatile, unlike the conventional gating effect, and the created new phases remain polar. Their origin, revealed by first-principles calculations, is related to the formation of metastable hydrogen-stabilized α-In2Se3 phases with switchable dipoles. Furthermore, our approach enables ultralow gate-voltage switching of different phases (below 0.4 V), and easy integration with transistor components. This work provides fundamental insights into the interactions between protons and ferroelectric phase transitions, providing a possible avenue for accessing hidden phases in ferroelectric switching and for developing energy-efficient, multilevel-switching memory devices. Copyright © 2023, The Authors. All rights reserved.

关键词： Van der Waals forces

Cholesterol allosteric modulation of the oxytocin receptor

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Biophysical Journal 2025年第12期124卷 1930-1943页

作者： Marlow, Brennica Vogel, Alexander Kuenze, Georg Pankonin, Maik Reinhardt, Franziska Stadler, Peter F. Hildebrand, Peter W. Meiler, Jens Center for Structural Biology Vanderbilt University Nashville TN United States Institute for Drug Discovery Medical Faculty Leipzig University Leipzig Germany Center for Scalable Data Analytics and Artificial Intelligence ScaDS.AI Leipzig University Leipzig Germany Interdisciplinary Center for Bioinformatics Leipzig University Leipzig Germany Chemical and Physical Biology Program Vanderbilt University Nashville TN United States Department of Chemistry Vanderbilt University Nashville TN United States Institute of Medical Physics and Biophysics Medical Faculty Leipzig University Leipzig Germany Bioinformatics Group Institute of Computer Science Interdisciplinary Center of Bioinformatics Leipzig University Leipzig Germany Max-Planck-Institute for Mathematics in the Sciences Leipzig Germany Institute of Theoretical Chemistry University of Vienna Wien Austria Facultad de Ciencias Universidad National de Colombia Sede Bogota Colombia Santa Fe Institute New Mexico Santa Fe Mexico

G-protein coupled receptors are critical components in cellular signaling, mediating various physiological responses to external stimuli. Here, we investigate the intricate relationship between cholesterol and the oxytocin receptor (OXTR), focusing on the binding mechanisms and the allosteric cross talk of bound cholesterol to the orthosteric ligand binding pocket. Utilizing molecular docking and molecular dynamics simulations, we identify cholesterol binding sites both on the agonist-bound and antagonist-bound state, which show differing distributions and residence times of the cholesterol molecules. Importantly, both methods converge on several key sites, demonstrating strong predictive overlap. Notably, one such site, and several sites detected by our molecular dynamics approach, also coincide with electron density observed in an experimental cryo-EM map, providing orthogonal validation for computational predictions. Allosteric network analysis uncovers the distinct pathways through which cholesterol may affect ligand-mediated receptor signaling, highlighting the significance of one site on the extracellular leaflet between TM4 and TM5, and two sites on the intracellular leaflet between TM2, TM3, and TM4 and between TM4 and TM5 in transmitting allosteric signals to the orthosteric pocket. These findings provide insights into the impact of cholesterol on OXTR function, emphasizing specific binding sites and signaling paths for further experimental exploration. © 2025 Biophysical Society

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Analysis of Some Parameters of Synthesized Anodized Aluminum Oxide Matrices

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Analysis of Some Parameters of Synthesized Anodized Aluminum...

International Conference on Modern Problems of Radio Engineering, Telecommunications and Computer science

作者： Roxoliana Bukliv Volodymyr Adamiv Ihor Bordun Nazariy Andrushchak Ihor Teslyuk Anatoliy Andrushchak Department of Chemistry and Technology of Inorganic Substances Institute of Chemistry and Chemical Technologies Lviv Polytechnic National University Lviv Ukraine O. G. Vlokh Institute of Physical Opics Ivan Franko National University of Lviv Lviv Ukraine Department of Electrical Power Engineering Czestochowa University of Technology Czestochowa Poland Department of Ecology and Sustainable Environmental Management Lviv Polytechnic National University Lviv Ukraine Computer-Aided Design Systems Lviv Politechnic National University Lviv Ukraine Department of Applied Physics and Nanomaterials Science Lviv Polytechnic National University Lviv Ukraine

ISBN: (数字)9798331520564

ISBN: (纸本)9798331520571

Studies have been conducted on anodized aluminum oxide (AAO) nanomatrices manufactured by SmartMembranes (SM) (Germany) and InRedox (USA). An X-ray fluorescence analyzer determined the quantitative and qualitative composition of AAO matrices. It is shown that the AAO matrices have a large transparency window (250 - 2750 nm) and the dependence of the second harmonic generation (SHG) signal on the pore size. The parameters of the porous structure of the samples were estimated by isothermal processes of nitrogen adsorption/desorption at its boiling point (T = 77 K).

关键词： Micrometers Sensitivity Fluorescence Market research Harmonic analysis Frequency conversion Telecommunications Nitrogen Isothermal processes Aluminum oxide

Spectroscopic origin of giant anomalous Hall effect in an interwoven magnetic kagome metal

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arXiv 2024年

作者： Cheng, Erjian Wang, Kaipu Hao, Yiqing Chen, Wenqing Tan, Hengxin Li, Zongkai Wang, Meixiao Gao, Wenli Wu, Di Sun, Shuaishuai Ying, Tianping Nie, Simin Li, Yiwei Schnelle, Walter Chen, Houke Zhou, Xingjiang Koban, Ralf Chen, Yulin Yan, Binghai Yang, Yifeng Wu, Weida Liu, Zhongkai Felser, Claudia Max Planck Institute for Chemical Physics of Solids Dresden01187 Germany School of Physical Science and Technology ShanghaiTech Laboratory for Topological Physics ShanghaiTech University Shanghai201210 China Neutron Scattering Division Oak Ridge National Laboratory P.0. Box 2008 Oak RidgeTN37831 United States Department of Physics & Astronomy Rutgers University PiscatawayNJ08854 United States Department of Condensed Matter Physics Weizmann Institute of Science Rehovot7610001 Israel University of Chinese Academy of Sciences Chinese Academy of Sciences Beijing100190 China Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing100190 China Department of Mechanical Engineering Stanford University StanfordCA94305 United States Wuhan University Wuhan430072 China Department of Physics University of Oxford OxfordOX1 3PU United Kingdom Songshan Lake Materials Laboratory Guangdong Dongguan523808 China

The discovery of a giant anomalous Hall effect (AHE) and its novel mechanism holds significant promise for advancing both fundamental research and practical applications. Magnetic kagome lattice materials are uniquely suited for studying the AHE due to their interplay between electronic structure, topology, and magnetism. However, the geometric frustration inherent in kagome lattices often limits the configuration and tunability of magnetic order. Here, we present a new design strategy for kagome-lattice materials with emergent magnetism, exemplified by the magnetic kagome metal TbTi3Bi4, which features interwoven magnetic Tb zigzag chains and non-magnetic Ti kagome bilayers. This material exhibits a record-high anomalous Hall conductivity (AHC) of 105 Ω−1cm−1. Spectroscopy measurements reveal a large band folding gap observed via angle-resolved photoemission spectroscopy, coexisting spin-density-wave (SDW) order detected through spin-polarized scanning tunneling spectroscopy, and a spiral magnetic order with large magnetic moments identified by neutron diffraction. These findings highlight a strong electron-magnetic coupling between itinerant charges and ordered magnetic moments, offering a spectroscopic explanation for the giant AHC in TbTi3Bi4. This work establishes a pathway for innovative material design strategies, unlocking new possibilities for future exploration and applications in quantum and spintronic technologies. © 2024, CC BY.

关键词： Spin density waves

Higher-Order Photon Statistics as a New Tool to Reveal Hidden Excited States in a Plasmonic Cavity

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arXiv 2021年

作者： Stegmann, Philipp Gupta, Satyendra Nath Haran, Gilad Cao, Jianshu Department of Chemistry Massachusetts Institute of Technology CambridgeMA02139 United States Department of Chemical and Biological Physics Weizmann Institute of Science Rehovot761001 Israel Physical Research Laboratory Ahmedabad380009 India

Among the best known quantities obtainable from photon correlation measurements are the g(m) correlation functions. Here, we introduce a new procedure to evaluate these correlation functions based on higher-order factorial cumulants CF,m which integrate over the time dependence of the correlation functions, i.e., summarize the available information at different time spans. In a systematic manner, the information content of higher-order correlation functions as well as the distribution of photon waiting times is taken into account. Our procedure greatly enhances the sensitivity for probing correlations and, moreover, is robust against a limited counting efficiency and time resolution in experiment. It can be applied even in case g(m) is not accessible at short time spans. We use the new evaluation scheme to analyze the photon emission of a plasmonic cavity coupled to a single quantum dot. We derive criteria which must hold if the system can be described by a generic Jaynes-Cummings model. A violation of the criteria can be explained by the presence of an additional excited quantum dot state. Copyright © 2021, The Authors. All rights reserved.

关键词： Nanocrystals

Coexistence of zero-, one- And two-dimensional degeneracy in tetragonal SnO2 phonons

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arXiv 2021年

作者： Wang, Jianhua Yuan, Hongkuan Kuang, Minquan Yang, Tie Yu, Zhi-Ming Zhang, Zeying Wang, Xiaotian School of Physical Science and Technology Southwest University Chongqing400715 China School of Physics Beijing Institute of Technology Beijing100081 China Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems School of Physics Beijing Institute of Technology Beijing100081 China College of Mathematics and Physics Beijing University of Chemical Technology Beijing100029 China

Based on the dimension of degeneracy, topological electronic systems can roughly be divided into three parts: nodal point, line and surface materials corresponding to zero-, one- and two-dimensional degeneracy, respectively. In parallel to electronic systems, the concept of topology was extended to phonons, promoting the birth of topological phonons. Till date, few nodal point, line and surface phonons candidates have been predicted in solid-state materials. In this study, based on symmetry analysis and first-principles calculation, for the first time, we prove that zero-, one- and two-dimensional degeneracy co-exist in the phonon dispersion of one single realistic solid-state material SnO2 with P42/mnm structure. In contrast to the previously reported electronic systems, the topological phonons observed in SnO2 are not restricted by the Pauli exclusion principle, and they experience negligible spin-orbit coupling effect. Hence, SnO2 with multiple dimensions of degeneracy phonons is a good platform for studying the entanglement among nodal point, line and surface phonons. Moreover, obvious phonon surface states are visible, which is beneficial for experimental detection. © 2021, CC BY.

关键词： Phonons

Synthesis of a semimetallic Weyl ferromagnet with point Fermi surface

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arXiv 2024年

作者： Belopolski, Ilya Watanabe, Ryota Sato, Yuki Yoshimi, Ryutaro Kawamura, Minoru Nagahama, Soma Zhao, Yilin Shao, Sen Jin, Yuanjun Kato, Yoshihiro Okamura, Yoshihiro Zhang, Xiao-Xiao Fujishiro, Yukako Takahashi, Youtarou Hirschberger, Max Tsukazaki, Atsushi Takahashi, Kei S. Chiu, Ching-Kai Chang, Guoqing Kawasaki, Masashi Nagaosa, Naoto Tokura, Yoshinori Saitama Wako351-0198 Japan University of Tokyo Tokyo113-8656 Japan Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 21 Nanyang Link 637371 Singapore Wuhan National High Magnetic Field Center School of Physics Huazhong University of Science and Technology Wuhan430074 China Saitama Wako351-0198 Japan Institute for Materials Research Tohoku University Miyagi Sendai980-8577 Japan Saitama Wako351-0198 Japan Fundamental Quantum Science Program TRIP Headquarters RIKEN Saitama Wako351-0198 Japan Tokyo College University of Tokyo Tokyo113-8656 Japan

Quantum materials governed by emergent topological fermions have become a cornerstone of physics. Dirac fermions in graphene form the basis for moiré quantum matter, and Dirac fermions in magnetic topological insulators enabled the discovery of the quantum anomalous Hall effect [1–3]. In contrast, there are few materials whose electromagnetic response is dominated by emergent Weyl fermions [4–6]. Nearly all known Weyl materials are overwhelmingly metallic, and are largely governed by irrelevant, conventional electrons. Here we theoretically predict and experimentally observe a semimetallic Weyl ferromagnet in van der Waals (Cr,Bi)2Te3. In transport, we find a record bulk anomalous Hall angle > 0.5 along with non-metallic conductivity, a regime sharply distinct from conventional ferromagnets. Together with symmetry analysis, our data suggest a semimetallic Fermi surface composed of two Weyl points, with a giant separation > 75% of the linear dimension of the bulk Brillouin zone, and no other electronic states. Using state-of-the-art crystal synthesis techniques, we widely tune the electronic structure, allowing us to annihilate the Weyl state and visualize a unique topological phase diagram exhibiting broad Chern insulating, Weyl semimetallic and magnetic semiconducting regions. Our observation of a semimetallic Weyl ferromagnet offers an avenue toward novel correlated states and non-linear phenomena, as well as zero-magnetic-field Weyl spintronic and optical devices. © 2024, CC BY.

关键词： Van der Waals forces