Physical Review X最新文献

{"title":"Theory of Electron-Phonon Interactions in Extended Correlated Systems Probed by Resonant Inelastic X-Ray Scattering","authors":"Jinu Thomas, Debshikha Banerjee, Alberto Nocera, Steven Johnston","doi":"10.1103/physrevx.15.021030","DOIUrl":"https://doi.org/10.1103/physrevx.15.021030","url":null,"abstract":"An emerging application of resonant inelastic x-ray scattering (RIXS) is the study of lattice excitations and electron-phonon (e</a:mi></a:math>-ph) interactions in quantum materials. Despite the growing importance of this area of research, the community lacks a complete understanding of how the RIXS process excites the lattice and how these excitations encode information about the <c:math xmlns:c=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><c:mi>e</c:mi></c:math>-ph interactions. Here, we present a detailed study of the RIXS spectra of the Hubbard-Holstein model defined on extended one-dimensional lattices. Using the density matrix renormalization group method, we compute the RIXS response while treating the electron mobility, many-body interactions, and core-hole interactions on an equal footing. The predicted spectra exhibit notable differences from those obtained using the commonly adopted Lang-Firsov models, with important implications for analyzing past and future experiments. Our results provide a deeper understanding of how RIXS probes <e:math xmlns:e=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><e:mi>e</e:mi></e:math>-ph interactions and set the stage for a more realistic analysis of future experiments. <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":"8 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143876065","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 Mixed Valence Model for Twisted Bilayer Graphene","authors":"Liam L. H. Lau, Piers Coleman","doi":"10.1103/physrevx.15.021028","DOIUrl":"https://doi.org/10.1103/physrevx.15.021028","url":null,"abstract":"Song and Bernevig (SB) have recently proposed a topological heavy-fermion description of the physics of magic angle twisted bilayer graphene (MATBG), involving the hybridization of flat-band electrons with a relativistic conduction sea. Here, we explore the consequences of this model, seeking a synthesis of understanding drawn from heavy-fermion physics and MATBG experiments. Our work identifies a key discrepancy between measured and calculated on-site Coulomb interactions, implicating renormalization effects that are not contained in the current model. With these considerations in mind, we consider a SB model with a single, renormalized on-site interaction between the f</a:mi></a:math> electrons, containing a phenomenological heavy-fermion binding potential on the moiré <c:math xmlns:c=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><c:mi>A</c:mi><c:mi>A</c:mi></c:math> sites. This feature allows the simplified model to capture the periodic reset of the chemical potential with filling and the observed stability of local moment behavior. We argue that a two-stage Kondo effect will develop in MATBG as a consequence of the relativistic conduction band: Kondo I occurs at high temperatures, establishing a coherent hybridization at the <e:math xmlns:e=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><e:mi mathvariant=\"normal\">Γ</e:mi></e:math> points and a non-Fermi liquid of incoherent fermions at the moiré <h:math xmlns:h=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><h:mi>K</h:mi></h:math> points; at much lower temperatures, Kondo II leads to a Fermi liquid in the flat band. Utilizing an auxiliary-rotor approach, we formulate a mean-field treatment of MATBG that captures this physics, describing the evolution of the normal state across a full range of filling factors. By contrasting the relative timescales of phonons and valence fluctuations in bulk heavy-fermion materials with that of MATBG, we are led to propose a valley-polaron origin to the Coulomb renormalization and the heavy-fermion binding potential identified from experiment. We also discuss the possibility that the two-fluid, non-Fermi liquid physics of the relativistic Kondo lattice is responsible for the strange-metal physics observed in MATBG. <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":"15 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143872863","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":"Theory of Fractional Quantum Hall Liquids Coupled to Quantum Light and Emergent Graviton-Polaritons","authors":"Zeno Bacciconi, Hernan B. Xavier, Iacopo Carusotto, Titas Chanda, Marcello Dalmonte","doi":"10.1103/physrevx.15.021027","DOIUrl":"https://doi.org/10.1103/physrevx.15.021027","url":null,"abstract":"Recent breakthrough experiments have demonstrated how it is now possible to explore the dynamics of quantum Hall states interacting with quantum electromagnetic cavity fields. While the impact of strongly coupled nonlocal cavity modes on integer quantum Hall physics has been recently addressed, the effects on fractional quantum Hall (FQH) liquids—and, more generally, fractionalized states of matter—remain largely unexplored. In this work, we develop a theoretical framework for the understanding of FQH states coupled to quantum light. In particular, combining analytical arguments with tensor network simulations, we study the dynamics of a ν</a:mi>=</a:mo>1</a:mn>/</a:mo>3</a:mn></a:math> Laughlin state in a single-mode cavity with finite electric field gradients. We find that the topological signatures of the FQH state remain robust against the nonlocal cavity vacuum fluctuations, as indicated by the endurance of the quantized Hall resistivity. The entanglement spectra, however, carry direct fingerprints of light-matter entanglement and topology, revealing peculiar polaritonic replicas of the U(1) counting. As a further response to cavity fluctuations, we also find a squeezed FQH geometry, encoded in long-wavelength correlations. By exploring the low-energy excited spectrum inside the FQH phase, we identify a new neutral quasiparticle, the graviton polariton, arising from the hybridization between quadrupolar FQH collective excitations (known as gravitons) and light. Pushing the light-matter interaction to ultrastrong-coupling regimes, we find other two important effects, a cavity vacuum-induced Stark shift for charged quasiparticles and a potential instability toward a density modulated stripe phase, competing against the phase separation driven by the Stark shift. Finally, we discuss the experimental implications of our findings and possible extension of our results to more complex scenarios. <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":"24 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143872864","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":"Effects of Polydispersity and Concentration on Elastocapillary Thinning of Dilute Polymer Solutions","authors":"Vincenzo Calabrese, Amy Q. Shen, Simon J. Haward","doi":"10.1103/physrevx.15.021025","DOIUrl":"https://doi.org/10.1103/physrevx.15.021025","url":null,"abstract":"The self-thinning of liquid bridges under the action of capillarity occurs in widespread processes like jetting, dripping, and spraying and gives rise to a strong extensional flow capable of stretching dissolved polymers. If the resulting elastic stress exceeds the viscous stress, an exponential “elastocapillary” (EC) thinning regime arises, yielding a timescale τ&lt;/a:mi&gt;EC&lt;/a:mi&gt;&lt;/a:mrow&gt;&lt;/a:msub&gt;&lt;/a:math&gt; that is commonly considered equivalent to the longest relaxation time of the polymer &lt;c:math xmlns:c=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;c:mi&gt;λ&lt;/c:mi&gt;&lt;/c:math&gt;. A long-standing question is why &lt;e:math xmlns:e=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;e:msub&gt;&lt;e:mi&gt;τ&lt;/e:mi&gt;&lt;e:mrow&gt;&lt;e:mi&gt;EC&lt;/e:mi&gt;&lt;/e:mrow&gt;&lt;/e:msub&gt;&lt;/e:math&gt; depends strongly on the polymer concentration, even at high dilutions where &lt;g:math xmlns:g=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;g:mi&gt;λ&lt;/g:mi&gt;&lt;/g:math&gt; should be constant in theory. To date, this is understood in terms of intermolecular interactions that arise due to “self-concentration” effects as polymers stretch. However, &lt;i:math xmlns:i=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;i:mi&gt;λ&lt;/i:mi&gt;&lt;/i:math&gt; depends on the polymer molecular weight &lt;k:math xmlns:k=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;k:mi&gt;M&lt;/k:mi&gt;&lt;/k:math&gt;, and we show how the concentration dependence of &lt;m:math xmlns:m=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;m:msub&gt;&lt;m:mi&gt;τ&lt;/m:mi&gt;&lt;m:mrow&gt;&lt;m:mi&gt;EC&lt;/m:mi&gt;&lt;/m:mrow&gt;&lt;/m:msub&gt;&lt;/m:math&gt; can be explained by considering the molecular weight distribution (MWD) inherent in real polymer samples, without the need to invoke self-concentration. We demonstrate this by blending low-&lt;o:math xmlns:o=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;o:mi&gt;M&lt;/o:mi&gt;&lt;/o:math&gt; and high-&lt;q:math xmlns:q=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;q:mi&gt;M&lt;/q:mi&gt;&lt;/q:math&gt; polymer samples with narrow MWDs at dilute concentrations and in different proportions and by measuring &lt;s:math xmlns:s=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;s:msub&gt;&lt;s:mi&gt;τ&lt;/s:mi&gt;&lt;s:mrow&gt;&lt;s:mi&gt;EC&lt;/s:mi&gt;&lt;/s:mrow&gt;&lt;/s:msub&gt;&lt;/s:math&gt; for each blend in capillary thinning experiments. Through a simple model that qualitatively reproduces the experimental results, we show how elastic stresses generated by the polymer build up prior to the EC regime due to the sequential stretching of progressively decreasing molecular weight species in the MWD. Since the elastic stress generated by each species depends on its concentration, the fraction of the MWD that is required to stretch in order to induce the EC regime depends on the total polymer concentration &lt;u:math xmlns:u=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;u:mi&gt;c&lt;/u:mi&gt;&lt;/u:math&gt; in the solution. For higher &lt;w:math xmlns:w=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;w:mi&gt;c&lt;/w:mi&gt;&lt;/w:math&gt;, the EC regime is induced by stretching of a higher-&lt;y:math xmlns:y=\"http://www.w3.org/1998/Math/Ma","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"13 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143866284","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":"Photocurrent Nanoscopy of Quantum Hall Bulk","authors":"Ran Jing, Boyi Zhou, Jiacheng Sun, Shoujing Chen, Wenjun Zheng, Zijian Zhou, Heng Wang, Lukas Wehmeier, Bing Cheng, Michael Dapolito, Yinan Dong, Zengyi Du, G. L. Carr, Xu Du, D. N. Basov, Qiang Li, Mengkun Liu","doi":"10.1103/physrevx.15.021026","DOIUrl":"https://doi.org/10.1103/physrevx.15.021026","url":null,"abstract":"Understanding nanoscale electronic and thermal transport of two-dimensional (2D) electron systems in the quantum Hall regime, particularly in the bulk insulating state, poses considerable challenges. One of the primary difficulties arises from the presence of chiral edge channels, whose transport behavior obscures the investigation of the insulating bulk. Using near-field optical and photocurrent nanoscopy, we probe real-space variations of the optical and thermal dynamics of graphene in the quantum Hall regime without relying on complex sample or electrode geometries. Near the charge-neutrality point, we detect strong optical and photothermal signals from resonant inter-Landau-level (LL) magnetoexciton excitations between the zeroth and ±</a:mo>1</a:mn></a:mrow></a:math> st LLs, which gradually weaken with increasing doping due to Pauli blocking. Interestingly, at higher doping levels and full-integer LL fillings, photothermal signals reappear across the entire sample over an approximately <c:math xmlns:c=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><c:mrow><c:mn>10</c:mn><c:mtext>−</c:mtext><c:mrow><c:mi mathvariant=\"normal\">μ</c:mi><c:mi mathvariant=\"normal\">m</c:mi></c:mrow></c:mrow></c:math> scale, indicating unexpectedly long cooling lengths and nonlocal photothermal heating through the insulating bulk. This observation suggests that thermal conductivity persists for the localized states even as electronic transport is suppressed—a clear violation of the Wiedemann-Franz law. Our experiments provide novel insights into nanoscale thermal and electronic transport in incompressible 2D gases, highlighting the roles of magnetoexcitons and chiral edge states in the thermo-optoelectric dynamics of the Dirac quantum Hall state. <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":"31 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143866336","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":"Probing Many-Body Bell Correlation Depth with Superconducting Qubits","authors":"Ke Wang, Weikang Li, Shibo Xu, Mengyao Hu, Jiachen Chen, Yaozu Wu, Chuanyu Zhang, Feitong Jin, Xuhao Zhu, Yu Gao, Ziqi Tan, Zhengyi Cui, Aosai Zhang, Ning Wang, Yiren Zou, Tingting Li, Fanhao Shen, Jiarun Zhong, Zehang Bao, Zitian Zhu, Zixuan Song, Jinfeng Deng, Hang Dong, Xu Zhang, Pengfei Zhang, Wenjie Jiang, Zhide Lu, Zheng-Zhi Sun, Hekang Li, Qiujiang Guo, Zhen Wang, Patrick Emonts, Jordi Tura, Chao Song, H. Wang, Dong-Ling Deng","doi":"10.1103/physrevx.15.021024","DOIUrl":"https://doi.org/10.1103/physrevx.15.021024","url":null,"abstract":"Quantum nonlocality describes a stronger form of quantum correlation than that of entanglement. It refutes Einstein’s belief of local realism and is among the most distinctive and enigmatic features of quantum mechanics. It is a crucial resource for achieving quantum advantages in a variety of practical applications, ranging from cryptography and certified random number generation via self-testing to machine learning. Nevertheless, the detection of nonlocality, especially in quantum many-body systems, is notoriously challenging. Here, we report an experimental certification of genuine multipartite Bell-operator correlations, which signal nonlocality in quantum many-body systems, up to 24 qubits with a fully programmable superconducting quantum processor. In particular, we employ energy as a Bell-operator correlation witness and variationally decrease the energy of a many-body system across a hierarchy of thresholds, below which an increasing Bell-operator correlation depth can be certified from experimental data. We variationally prepare the low-energy state of a two-dimensional honeycomb model with 73 qubits and certify its Bell-operator correlations by measuring an energy that surpasses the corresponding classical bound with up to 48 standard deviations. In addition, we variationally prepare a sequence of low-energy states and certify their genuine multipartite Bell-operator correlations up to 24 qubits via energies measured efficiently by parity oscillation and multiple quantum coherence techniques. Our results establish a viable approach for preparing and certifying multipartite Bell-operator correlations, which provide not only a finer benchmark beyond entanglement for quantum devices, but also a valuable guide toward exploiting multipartite Bell correlations in a wide spectrum of practical applications. <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":"108 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143862117","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":"Unitary k -Designs from Random Number-Conserving Quantum Circuits","authors":"Sumner N. Hearth, Michael O. Flynn, Anushya Chandran, Chris R. Laumann","doi":"10.1103/physrevx.15.021022","DOIUrl":"https://doi.org/10.1103/physrevx.15.021022","url":null,"abstract":"Local random circuits scramble efficiently and, accordingly, have a range of applications in quantum information and quantum dynamics. With a global U(1) charge, however, the scrambling ability is reduced; for example, such random circuits do not generate the entire group of number-conserving unitaries. We establish two results using the statistical mechanics of k&lt;/a:mi&gt;&lt;/a:math&gt;-fold replicated circuits. First, we show that finite moments cannot distinguish the ensemble that local random circuits generate from the Haar ensemble on the entire group of number-conserving unitaries. Specifically, the circuits form a &lt;c:math xmlns:c=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;c:msub&gt;&lt;c:mi&gt;k&lt;/c:mi&gt;&lt;c:mi&gt;c&lt;/c:mi&gt;&lt;/c:msub&gt;&lt;/c:math&gt;-design with &lt;e:math xmlns:e=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;e:msub&gt;&lt;e:mi&gt;k&lt;/e:mi&gt;&lt;e:mi&gt;c&lt;/e:mi&gt;&lt;/e:msub&gt;&lt;e:mo&gt;=&lt;/e:mo&gt;&lt;e:mi&gt;O&lt;/e:mi&gt;&lt;e:mo stretchy=\"false\"&gt;(&lt;/e:mo&gt;&lt;e:msup&gt;&lt;e:mi&gt;L&lt;/e:mi&gt;&lt;e:mi&gt;d&lt;/e:mi&gt;&lt;/e:msup&gt;&lt;e:mo stretchy=\"false\"&gt;)&lt;/e:mo&gt;&lt;/e:math&gt; for a system in &lt;i:math xmlns:i=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;i:mi&gt;d&lt;/i:mi&gt;&lt;/i:math&gt; spatial dimensions with linear dimension &lt;k:math xmlns:k=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;k:mi&gt;L&lt;/k:mi&gt;&lt;/k:math&gt;. Second, for &lt;m:math xmlns:m=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;m:mi&gt;k&lt;/m:mi&gt;&lt;m:mo&gt;&lt;&lt;/m:mo&gt;&lt;m:msub&gt;&lt;m:mi&gt;k&lt;/m:mi&gt;&lt;m:mi&gt;c&lt;/m:mi&gt;&lt;/m:msub&gt;&lt;/m:math&gt;, we derive bounds on the depth &lt;o:math xmlns:o=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;o:mi&gt;τ&lt;/o:mi&gt;&lt;/o:math&gt; required for the circuit to converge to an approximate &lt;q:math xmlns:q=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;q:mi&gt;k&lt;/q:mi&gt;&lt;/q:math&gt;-design. The depth is lower bounded by diffusion &lt;s:math xmlns:s=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;s:mi&gt;k&lt;/s:mi&gt;&lt;s:msup&gt;&lt;s:mi&gt;L&lt;/s:mi&gt;&lt;s:mn&gt;2&lt;/s:mn&gt;&lt;/s:msup&gt;&lt;s:mi&gt;ln&lt;/s:mi&gt;&lt;s:mo stretchy=\"false\"&gt;(&lt;/s:mo&gt;&lt;s:mi&gt;L&lt;/s:mi&gt;&lt;s:mo stretchy=\"false\"&gt;)&lt;/s:mo&gt;&lt;s:mo&gt;≲&lt;/s:mo&gt;&lt;s:mi&gt;τ&lt;/s:mi&gt;&lt;/s:math&gt;. In contrast, without number conservation &lt;w:math xmlns:w=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;w:mi&gt;τ&lt;/w:mi&gt;&lt;w:mo&gt;∼&lt;/w:mo&gt;&lt;w:mrow&gt;&lt;w:mi&gt;poly&lt;/w:mi&gt;&lt;/w:mrow&gt;&lt;w:mo stretchy=\"false\"&gt;(&lt;/w:mo&gt;&lt;w:mi&gt;k&lt;/w:mi&gt;&lt;w:mo stretchy=\"false\"&gt;)&lt;/w:mo&gt;&lt;w:mi&gt;L&lt;/w:mi&gt;&lt;/w:math&gt;. The convergence of the circuit ensemble is controlled by the low-energy properties of a frustration-free quantum statistical model which spontaneously breaks k&lt;/ab:mi&gt;&lt;/ab:math&gt; U(1) symmetries. We conjecture that the associated Goldstone modes set the spectral gap for arbitrary spatial and qudit dimensions, leading to an upper bound &lt;cb:math xmlns:cb=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"&gt;&lt;cb:mi&gt;τ&lt;/cb:mi&gt;&lt;cb:mo&gt;≲&lt;/cb:mo&gt;&lt;cb:mi&gt;k&lt;/cb:mi&gt;&lt;cb:msup&gt;&lt;cb:mi&gt;L&lt;/cb:mi&gt;&lt;cb:mrow&gt;&lt;cb:mi&gt;d&lt;/cb:mi&gt;&lt;cb:mo&gt;+&lt;/cb:mo&gt;&lt;cb:mn&gt;2&lt;/cb:mn&gt;&lt;/cb:mrow&gt;&lt;/cb:msup&gt;&lt;/cb:math&gt;. &lt;jats:supplementary-material&gt; &lt;jats:copyright-statement&gt;Published by the American Physical Society&lt;/jats:copyright-statement&gt; &lt;jats:copyright-y","PeriodicalId":20161,"journal":{"name":"Physical Review X","volume":"17 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143857741","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":"Pulling Order Back from the Brink of Disorder: Observation of a Nodal-Line Spin Liquid and Fluctuation Stabilized Order in K2IrCl6","authors":"Qiaochu Wang, Alberto de la Torre, Jose A. Rodriguez-Rivera, Andrey A. Podlesnyak, Wei Tian, Adam A. Aczel, Masaaki Matsuda, Philip J. Ryan, Jong-Woo Kim, Jeffrey G. Rau, Kemp W. Plumb","doi":"10.1103/physrevx.15.021021","DOIUrl":"https://doi.org/10.1103/physrevx.15.021021","url":null,"abstract":"Competing interactions in frustrated magnets can give rise to highly degenerate ground states from which correlated liquidlike states of matter often emerge. The scaling of this degeneracy influences the ultimate ground state, with extensive degeneracies potentially yielding quantum spin liquids, while subextensive or smaller degeneracies yield static orders. A long-standing problem is to understand how ordered states precipitate from this degenerate manifold and what echoes of the degeneracy survive ordering. Here, we use neutron scattering to experimentally demonstrate a new “nodal-line” spin liquid, where spins collectively fluctuate within a subextensive manifold spanning one-dimensional lines in reciprocal space. Realized in the spin-orbit-coupled, face-centered-cubic iridate K</a:mi>2</a:mn></a:msub>IrCl</a:mi>6</a:mn></a:msub></a:math>, we show that the subextensive degeneracy is robust, but remains susceptible to fluctuations or longer-range interactions which cooperate to select a magnetic order at low temperatures. Proximity to the nodal-line spin liquid influences the ordered state, enhancing the effects of quantum fluctuations that in turn act to stabilize the sublattice magnetization through the self-consistent opening of a large spin-wave gap. Our results demonstrate how quantum fluctuations can act counterintuitively in frustrated materials: Even in a case where fluctuations are ineffective at selecting an ordered state from a degenerate manifold, at the brink of the nodal spin liquid, they can act to protect the ordered state and dictate its low-energy physics. <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":"29 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143857742","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":"Theory of Free Fermions Dynamics under Partial Postselected Monitoring","authors":"Chun Y. Leung, Dganit Meidan, Alessandro Romito","doi":"10.1103/physrevx.15.021020","DOIUrl":"https://doi.org/10.1103/physrevx.15.021020","url":null,"abstract":"Monitored quantum systems undergo measurement-induced phase transitions (MiPTs) stemming from the interplay between measurements and unitary dynamics. When the detector readout is postselected to match a given value, the dynamics is generated by a non-Hermitian Hamiltonian with MiPTs characterized by different universal features. Here, we derive a stochastic Schrödinger equation based on a microscopic description of continuous weak measurement. This formalism connects the monitored and postselected dynamics to a broader family of stochastic evolution. We apply the formalism to a chain of free fermions subject to partial postselected monitoring of local fermion parities. Within a two-replica approach, we obtain an effective bosonized Hamiltonian in the strong postselected limit. Using a renormalization group analysis, we find that the universality of the non-Hermitian MiPT is stable against a finite (weak) amount of stochasticity. We further show that the passage to the monitored universality occurs abruptly at finite partial postselection, which we confirm from the numerical finite size scaling of the MiPT. Our approach establishes a way to study MiPTs for arbitrary subsets of quantum trajectories and provides a potential route to tackle the experimental postselected problem. <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":"28 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143846634","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":"A Quantum Critical Line Bounds the High Field Metamagnetic Transition Surface in UTe2","authors":"Z. Wu, T. I. Weinberger, A. J. Hickey, D. V. Chichinadze, D. Shaffer, A. Cabala, H. Chen, M. Long, T. J. Brumm, W. Xie, Y. Ling, Z. Zhu, Y. Skourski, D. E. Graf, V. Sechovský, M. Vališka, G. G. Lonzarich, F. M. Grosche, A. G. Eaton","doi":"10.1103/physrevx.15.021019","DOIUrl":"https://doi.org/10.1103/physrevx.15.021019","url":null,"abstract":"Quantum critical phenomena are widely studied across various materials families, from high-temperature superconductors to magnetic insulators. They occur when a thermodynamic phase transition is suppressed to zero temperature as a function of some tuning parameter such as pressure or magnetic field. This generally yields a point of instability—a so-called quantum critical point—at which the phase transition is driven exclusively by quantum fluctuations. Here, we show that the heavy fermion metamagnet UTe</a:mi></a:mrow>2</a:mn></a:mrow></a:msub></a:mrow></a:math> possesses a quantum phase transition at extreme magnetic field strengths of over 70 T. Rather than terminating at one singular point, we find that the phase boundary is sensitive to magnetic field components in each of the three Cartesian axes of magnetic field space. This results in the transition surface being bounded by a continuous ring of quantum critical points, the locus of which forms an extended line of quantum criticality—a novel form of quantum critical phase boundary. Within this quantum critical line sits a magnetic field-induced superconducting state in a toroidal shape, which persists to fields over 70 T. We model our data by a phenomenological free energy expansion and show how a quantum critical line—rather than a more conventional singular point of instability—anchors the remarkable high magnetic field phase landscape of <c:math xmlns:c=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><c:mrow><c:msub><c:mrow><c:mi>UTe</c:mi></c:mrow><c:mrow><c:mn>2</c:mn></c:mrow></c:msub></c:mrow></c:math>. <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":"25 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143846556","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}