Physical Review X最新文献

{"title":"Beyond-Hubbard Pairing in a Cuprate Ladder","authors":"Hari Padma, Jinu Thomas, Sophia F. R. TenHuisen, Wei He, Ziqiang Guan, Jiemin Li, Byungjune Lee, Yu Wang, Seng Huat Lee, Zhiqiang Mao, Hoyoung Jang, Valentina Bisogni, Jonathan Pelliciari, Mark P. M. Dean, Steven Johnston, Matteo Mitrano","doi":"10.1103/physrevx.15.021049","DOIUrl":"https://doi.org/10.1103/physrevx.15.021049","url":null,"abstract":"The Hubbard model is believed to capture the essential physics of cuprate superconductors. However, recent theoretical studies suggest that it fails to reproduce a robust and homogeneous superconducting ground state. Here, using resonant inelastic x-ray scattering and density matrix renormalization group calculations, we show that magnetic excitations in the prototypical cuprate ladder Sr</a:mi></a:mrow>14</a:mn></a:mrow></a:msub>Cu</a:mi></a:mrow>24</a:mn></a:mrow></a:msub>O</a:mi></a:mrow>41</a:mn></a:mrow></a:msub></a:mrow></a:math> are inconsistent with those of a simple Hubbard model. The magnetic response of hole carriers, contributing to an emergent branch of spin-flip excitations, is strongly suppressed. This effect is the consequence of strong <d:math xmlns:d=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><d:mi>d</d:mi></d:math>-wavelike pairing, enhanced by nearly an order of magnitude through a large nearest-neighbor attractive interaction and persisting up to at least 260 K. The close connection between the physics of cuprate ladders and that of the two-dimensional compounds suggests that such an enhanced hole pairing may be a universal feature of superconducting cuprates. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"1 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143940286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Superconductivity in the Parent Infinite-Layer Nickelate NdNiO2","authors":"C. T. Parzyck, Y. Wu, L. Bhatt, M. Kang, Z. Arthur, T. M. Pedersen, R. Sutarto, S. Fan, J. Pelliciari, V. Bisogni, G. Herranz, A. B. Georgescu, D. G. Hawthorn, L. F. Kourkoutis, D. A. Muller, D. G. Schlom, K. M. Shen","doi":"10.1103/physrevx.15.021048","DOIUrl":"https://doi.org/10.1103/physrevx.15.021048","url":null,"abstract":"We report evidence for superconductivity with onset temperatures up to 11 K in thin films of the infinite-layer nickelate parent compound NdNiO</a:mi></a:mrow>2</a:mn></a:mrow></a:msub></a:mrow></a:math>. A combination of oxide molecular beam epitaxy and atomic hydrogen reduction yields samples with high crystallinity and low residual resistivities, a substantial fraction of which exhibit superconducting transitions. We survey a large series of samples with a variety of techniques, including electrical transport, scanning transmission electron microscopy, x-ray absorption spectroscopy, and resonant inelastic x-ray scattering, to investigate the possible origins of superconductivity. We propose that superconductivity could be intrinsic to the undoped infinite-layer nickelates but suppressed by disorder due to a possibly sign-changing order parameter, a finding which would necessitate a reconsideration of the nickelate phase diagram. Another possible hypothesis is that the parent materials can be hole doped from randomly dispersed apical oxygen atoms, which would suggest an alternative pathway for achieving superconductivity. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"55 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143940287","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unifying Non-Markovian Characterization with an Efficient and Self-Consistent Framework","authors":"G. A. L. White, P. Jurcevic, C. D. Hill, K. Modi","doi":"10.1103/physrevx.15.021047","DOIUrl":"https://doi.org/10.1103/physrevx.15.021047","url":null,"abstract":"Noise on quantum devices is much more complex than it is commonly given credit. Far from usual models of decoherence, nearly all quantum devices are plagued by both a continuum of environments and temporal instabilities. These induce noisy quantum and classical correlations at the level of the circuit. The relevant spatiotemporal effects are difficult enough to understand, let alone combat. There is presently a lack of either scalable or complete methods to address the phenomena responsible for scrambling and loss of quantum information. Here, we make deep strides to remedy this problem. We establish a theoretical framework that uniformly incorporates and classifies all non-Markovian phenomena. Our framework is universal, assumes no parameters values, and is written entirely in terms of experimentally accessible circuit-level quantities. We formulate an efficient reconstruction using tensor network learning, allowing also for easy modularization and simplification based on the expected physics of the system. This is then demonstrated through both extensive numerical studies and implementations on IBM Quantum devices, estimating a comprehensive set of spacetime correlations. Finally, we conclude our analysis with applications thereof to the efficacy of control techniques to counteract these effects—including noise-aware circuit compilation and optimized dynamical decoupling. We find significant improvements are possible in the diamond norm and average gate fidelity of arbitrary SU(4) operations, as well as related decoupling improvements in contrast to off-the-shelf schemes. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"16 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143930680","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Isotope Substitution and Polytype Control for Point Defects Identification: The Case of the Ultraviolet Color Center in Hexagonal Boron Nitride","authors":"J. Plo, A. Pershin, S. Li, T. Poirier, E. Janzen, H. Schutte, M. Tian, M. Wynn, S. Bernard, A. Rousseau, A. Ibanez, P. Valvin, W. Desrat, T. Michel, V. Jacques, B. Gil, A. Kaminska, N. Wan, J. H. Edgar, A. Gali, G. Cassabois","doi":"10.1103/physrevx.15.021045","DOIUrl":"https://doi.org/10.1103/physrevx.15.021045","url":null,"abstract":"Defects in crystals can have a transformative effect on the properties and functionalities of solid-state systems. Dopants in semiconductors are core components in electronic and optoelectronic devices. The control of single color centers is at the basis of advanced applications for quantum technologies. Unintentional defects can also be detrimental to the crystalline structure and hinder the development of novel materials. Whatever the research perspective, the identification of defects is a key, but complicated, and often long-standing issue. Here, we present a general methodology to identify point defects by combining isotope substitution and polytype control, with a systematic comparison between experiments and first-principles calculations. We apply this methodology to hexagonal boron nitride (h</a:mi></a:math>-BN) and its ubiquitous color center emitting in the ultraviolet spectral range. From isotopic purification of the host <c:math xmlns:c=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><c:mi>h</c:mi></c:math>-BN matrix, a local vibrational mode of the defect is uncovered, and isotope-selective carbon doping proves that this mode belongs to a carbon-based center. Then, by varying the stacking sequence of the host <e:math xmlns:e=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><e:mi>h</e:mi></e:math>-BN matrix, we unveil different optical responses to hydrostatic pressure for the nonequivalent configurations of this ultraviolet color center. We conclude that this defect is a carbon dimer in the honeycomb lattice of <g:math xmlns:g=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><g:mi>h</g:mi></g:math>-BN. Our results show that tuning the stacking sequence in different polytypes of a given crystal provides unique fingerprints contributing to the identification of defects in 2D materials. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"1 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143927201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Small Polaron-Induced Ultrafast Ferroelectric Restoration in BiFeO3","authors":"Wenfan Chen, Tian Wang, Chun-Chieh Yu, Yuancheng Jing, Xiaosong Li, Wei Xiong","doi":"10.1103/physrevx.15.021046","DOIUrl":"https://doi.org/10.1103/physrevx.15.021046","url":null,"abstract":"In this report, we apply a suite of ultrafast spectroscopic techniques and advanced calculations to reveal the interplay between electronic and lattice degrees of freedom in ferroelectric BiFeO</a:mi></a:mrow>3</a:mn></a:mrow></a:msub></a:mrow></a:math>. Using transient sum frequency generation spectroscopy, which is sensitive to electronic polarizations, we observe a transient electronic dipole reduction upon optical excitation which recovers at 0.5 and 10 ps timescale. The time-dependent density functional theory calculation reveals that both ligand-metal charge transfer and local excitation transition occurred upon photo excitation. To reveal the nature of electronic dipole restoration, we employ transient extreme ultraviolet (EUV) spectroscopy—an element-specific ultrafast technique that follows charge dynamics of Bi, Fe, and O altogether. The transient EUV dynamics observed both ultrafast free charge carrier relaxation to excitons, as well as polaron formation. However, a timescale comparison suggests that only the polaron formation is responsible for the 0.5 ps electronic dipole restoration, whereas the faster electronic relaxation does not contribute to the ferroelectric property changes. Multireference configuration interaction calculation further corroborates this result by showing both Fe and Bi atoms shift from the ground state equilibrium—leading to the polaron formation. Our result disentangles the multidegrees of freedom in ultrafast ferroelectric modulation and identifies the pivotal motion—a local polaron formation—for the fast ferroelectric recovery. It provides crucial insights on the specific lattice distortion that could modulate properties or phase transitions of condensed matter materials. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"20 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143926851","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multiscale Field Theory for Network Flows","authors":"Guram Mikaberidze, Oriol Artime, Albert Díaz-Guilera, Raissa M. D’Souza","doi":"10.1103/physrevx.15.021044","DOIUrl":"https://doi.org/10.1103/physrevx.15.021044","url":null,"abstract":"Network flows are pervasive, including the movement of people, transportation of goods, transmission of energy, and dissemination of information; they occur on a range of empirical interconnected systems, from designed infrastructure to naturally evolved networks. Despite the broad spectrum of applications, because of their domain-specific nature and the inherent analytic complexity, a comprehensive theory of network flows is lacking. We introduce a unifying treatment for network flows that considers the fundamental properties of packet symmetries, conservation laws, and routing strategies. For example, electrons in power grids possess interchangeability symmetry, unlike packages sent by postal mail, which are distinguishable. Likewise, packets can be conserved, such as cars in road networks, or dissipated, such as Internet packets that time out. We introduce a hierarchy of analytical field-theoretic approaches to capture the different scales of complexity required. Mean-field analysis uncovers the nature of the transition through which flow becomes unsustainable upon unchecked growth of demand. Mesoscopic field theory accurately accounts for complicated network structures, packet symmetries, and conservation laws and yet is capable of admitting closed-form solutions. Finally, the full-scale field theory allows us to study routing strategies ranging from random diffusion to shortest path. Our theoretical results indicate that flow bottlenecks tend to be near sources for interchangeable packets and near sinks for distinguishable ones, and that dissipation hinders the maximum sustainable throughput for interchangeable packets but can enhance throughput for distinguishable packets. Finally, we showcase the flexibility of our multiscale theory by applying it in two distinct domains of road networks and the neuronal network. Our work paves the way for a more unifying and comprehensive theory of network flows. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"12 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143920326","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Symmetry-Dependent Dielectric Screening of Optical Phonons in Monolayer Graphene","authors":"Loïc Moczko, Sven Reichardt, Aditya Singh, Xin Zhang, Elise Jouaiti, Luis E. Parra López, Joanna L. P. Wolff, Aditi Raman Moghe, Etienne Lorchat, Rajendra Singh, Kenji Watanabe, Takashi Taniguchi, Hicham Majjad, Michelangelo Romeo, Arnaud Gloppe, Ludger Wirtz, Stéphane Berciaud","doi":"10.1103/physrevx.15.021043","DOIUrl":"https://doi.org/10.1103/physrevx.15.021043","url":null,"abstract":"Quantized lattice vibrations (i.e., phonons) in solids are robust and unambiguous fingerprints of crystal structures and of their symmetry properties. In metals and semimetals, strong electron-phonon coupling may lead to so-called Kohn anomalies in the phonon dispersion, providing an image of the Fermi surface in a nonelectronic observable. Kohn anomalies become prominent in low-dimensional systems, in particular, in graphene, where they appear as sharp kinks in the in-plane optical phonon branches. However, in spite of intense research efforts on electron-phonon coupling in graphene and related van der Waals heterostructures, little is known regarding the links between the symmetry properties of optical phonons at and near Kohn anomalies and their sensitivity towards the local environment. Here, using inelastic light scattering (Raman) spectroscopy, we investigate a set of custom-designed graphene-based van der Waals heterostructures, wherein dielectric screening is finely controlled at the atomic-layer level. We demonstrate experimentally and explain theoretically that, depending exclusively on their symmetry properties, the two main Raman lines of graphene react differently to the surrounding environment. While the 2D line, which is due to near-zone-edge optical phonons, undergoes changes due to the neighboring dielectric environment, the in-plane, zone-center optical phonons are symmetry protected from the influence of the latter. These results shed new light on the unique electron-phonon coupling properties in graphene and related systems and provide invaluable guidelines to characterize dielectric screening in van der Waals heterostructures and moiré superlattices. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"66 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143920125","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Theoretical Lower Limit of Coercive Field in Ferroelectric Hafnia","authors":"Jiyuan Yang, Jing Wu, Jingxuan Li, Chao Zhou, Yang Sun, Zuhuang Chen, Shi Liu","doi":"10.1103/physrevx.15.021042","DOIUrl":"https://doi.org/10.1103/physrevx.15.021042","url":null,"abstract":"The high coercive field (E&lt;/a:mi&gt;c&lt;/a:mi&gt;&lt;/a:msub&gt;&lt;/a:math&gt;) of hafnia-based ferroelectrics presents a major obstacle to their applications. The ferroelectric switching mechanisms in hafnia that dictate &lt;d:math xmlns:d=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;d:msub&gt;&lt;d:mi mathvariant=\"script\"&gt;E&lt;/d:mi&gt;&lt;d:mi&gt;c&lt;/d:mi&gt;&lt;/d:msub&gt;&lt;/d:math&gt;, especially those related to domain nucleation in the nucleation-limited-switching (NLS) model and domain-wall motion in the Kolmogorov-Avrami-Ishibashi (KAI) model, have remained elusive. We develop a deep-learning-assisted multiscale approach, incorporating atomistic insights into the critical nucleus, to predict both NLS- and KAI-type coercive fields. The theoretical NLS-type &lt;g:math xmlns:g=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;g:msub&gt;&lt;g:mi mathvariant=\"script\"&gt;E&lt;/g:mi&gt;&lt;g:mi&gt;c&lt;/g:mi&gt;&lt;/g:msub&gt;&lt;/g:math&gt; values agree with previous experimental results as well as our own measurements and also exhibit the correct thickness scaling for films between 3 and 20 nm. Combined theoretical and experimental investigations reveal that the giant &lt;j:math xmlns:j=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;j:msub&gt;&lt;j:mi mathvariant=\"script\"&gt;E&lt;/j:mi&gt;&lt;j:mi&gt;c&lt;/j:mi&gt;&lt;/j:msub&gt;&lt;/j:math&gt; in hafnia-based ferroelectrics arises from the ultrathin geometry, which confines switching to the NLS mechanism. We predict that the theoretical lower limit for KAI-type &lt;m:math xmlns:m=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;m:msub&gt;&lt;m:mi mathvariant=\"script\"&gt;E&lt;/m:mi&gt;&lt;m:mi&gt;c&lt;/m:mi&gt;&lt;/m:msub&gt;&lt;/m:math&gt; is &lt;p:math xmlns:p=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;p:mrow&gt;&lt;p:mn&gt;0.1&lt;/p:mn&gt;&lt;p:mtext&gt; &lt;/p:mtext&gt;&lt;p:mtext&gt; &lt;/p:mtext&gt;&lt;p:mi&gt;MV&lt;/p:mi&gt;&lt;p:mo&gt;/&lt;/p:mo&gt;&lt;p:mi&gt;cm&lt;/p:mi&gt;&lt;/p:mrow&gt;&lt;/p:math&gt; arising from mobile domain walls. The activation of KAI-type switching to achieve lower &lt;r:math xmlns:r=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;r:msub&gt;&lt;r:mi mathvariant=\"script\"&gt;E&lt;/r:mi&gt;&lt;r:mi&gt;c&lt;/r:mi&gt;&lt;/r:msub&gt;&lt;/r:math&gt; is supported by our experimental demonstration of a low coercive field of &lt;u:math xmlns:u=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;u:mrow&gt;&lt;u:mn&gt;1&lt;/u:mn&gt;&lt;u:mtext&gt; &lt;/u:mtext&gt;&lt;u:mtext&gt; &lt;/u:mtext&gt;&lt;u:mi&gt;MV&lt;/u:mi&gt;&lt;u:mo&gt;/&lt;/u:mo&gt;&lt;u:mi&gt;cm&lt;/u:mi&gt;&lt;/u:mrow&gt;&lt;/u:math&gt; in 60 nm ferroelectric &lt;w:math xmlns:w=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;w:mrow&gt;&lt;w:mo stretchy=\"false\"&gt;(&lt;/w:mo&gt;&lt;w:mrow&gt;&lt;w:msub&gt;&lt;w:mrow&gt;&lt;w:mi&gt;HfO&lt;/w:mi&gt;&lt;/w:mrow&gt;&lt;w:mrow&gt;&lt;w:mn&gt;2&lt;/w:mn&gt;&lt;/w:mrow&gt;&lt;/w:msub&gt;&lt;/w:mrow&gt;&lt;w:msub&gt;&lt;w:mrow&gt;&lt;w:mo stretchy=\"false\"&gt;)&lt;/w:mo&gt;&lt;/w:mrow&gt;&lt;w:mrow&gt;&lt;w:mi&gt;n&lt;/w:mi&gt;&lt;/w:mrow&gt;&lt;/w:msub&gt;&lt;w:mo&gt;/&lt;/w:mo&gt;&lt;w:mo stretchy=\"false\"&gt;(&lt;/w:mo&gt;&lt;w:mrow&gt;&lt;w:msub&gt;&lt;w:mrow&gt;&lt;w:mi&gt;ZrO&lt;/w:mi&gt;&lt;/w:mrow&gt;&lt;w:mrow&gt;&lt;w:mn&gt;2&lt;/w:mn&gt;&lt;/w:mrow&gt;&lt;/w:msub&gt;&lt;/w:mrow&gt;&lt;w:msub&gt;&lt;w:mrow&gt;&lt;w:mo stretchy=\"false\"&gt;)&lt;/w:mo&gt;&lt;/w:mrow&gt;&lt;w:mrow&gt;&lt;w:mi&gt;n&lt;/w:mi&gt;&lt;/w:mrow&gt;&lt;/w:msub&gt;&lt;/w:mrow&gt;&lt;/w:math&gt; (&lt;cb:math xmlns:cb=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;cb:mi&gt;n&lt;/cb:mi&gt;&lt;cb:mo&gt;=&lt;/cb:mo&gt;&lt;cb:mn&gt;3&lt;/cb:mn&gt;&lt;/cb:math&gt; unit cel","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"25 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143915437","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Topological Meron-Antimeron Domain Walls and Skyrmions in a Low-Symmetry System","authors":"Reiner Brüning, Levente Rózsa, Roberto Lo Conte, André Kubetzka, Roland Wiesendanger, Kirsten von Bergmann","doi":"10.1103/physrevx.15.021041","DOIUrl":"https://doi.org/10.1103/physrevx.15.021041","url":null,"abstract":"The generation of topologically nontrivial magnetic configurations has been a pivotal topic in both basic and applied nanomagnetism research. Localized noncoplanar magnetic defects such as skyrmions or merons were found to interact strongly with currents, making them interesting candidates for future spintronics applications. So far, mostly systems with a high rotational symmetry have been investigated where skyrmions were axially symmetric. Here, we study a low-symmetry system by spin-polarized scanning tunneling microscopy and an atomistic spin model using parameters based on first-principles calculations. We demonstrate how a delicate balance between energy terms generates both topologically trivial and nontrivial domain walls, depending on their nonequivalent crystallographic direction. The topological walls consist of alternating merons and antimerons, and the topological charge is 1 for every 6-nm length of the wall. The incorporation of holes in the films facilitates the transition from an in-plane ferromagnetic ground state to a spin-spiral state. Both domain walls and spirals transition into isolated elongated magnetic skyrmions in applied magnetic fields. These findings establish low-symmetry systems as a versatile platform for spin-texture engineering. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"50 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143915436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Realistic Ab Initio Predictions of Excimer Behavior under Collective Light-Matter Strong Coupling","authors":"Matteo Castagnola, Marcus T. Lexander, Henrik Koch","doi":"10.1103/physrevx.15.021040","DOIUrl":"https://doi.org/10.1103/physrevx.15.021040","url":null,"abstract":"Experiments show that light-matter strong coupling affects chemical properties, though the underlying mechanism remains unclear. A major challenge is to perform reliable and affordable simulation of molecular behavior when many molecules are collectively coupled to the same optical mode. This paper presents an quantum electrodynamics coupled cluster method for the collective strong coupling regime. The model describes electronic and electron-photon correlation within a molecular subsystem, while a simplified description of the collective polaritonic excitations allows for a realistic microscopic light-matter coupling. The developed framework provides a computationally tractable route to accurately simulate a molecule in a collective environment, which is unfeasible when several molecules are treated explicitly. We investigate the properties of the argon dimer under strong light-matter coupling. In the single-molecule regime (large light-matter coupling), the potential energies are substantially modified, weakening the excimer bond. In contrast, in the collective regime (small light-matter coupling, large number of molecules), the ground state potential energy surface and the first vibrational levels of the excited state do not change significantly. However, collective strong coupling produces an abrupt transition in the vibrational landscape of the excimer, causing higher vibrational levels to behave similarly to the vibrations in the ground state. We expect the excimer formation to be inhibited by light-matter strong coupling and conclude that chemical properties are altered via distinct mechanisms in the collective and single-molecule regimes. We also discuss fundamental aspects of polaritonic chemistry, such as resonance conditions and sudden changes of the molecular properties when a critical collective coupling strength is achieved. <jats:supplementary-material> <jats:copyright-statement>Published by the American Physical Society</jats:copyright-statement> <jats:copyright-year>2025</jats:copyright-year> </jats:permissions> </jats:supplementary-material>","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"11 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143909768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}