Pub Date : 2025-01-24DOI: 10.1103/physrevx.15.011013
Florian Sammüller, Matthias Schmidt, Robert Evans
We use supervised machine learning together with the concepts of classical density functional theory to investigate the effects of interparticle attraction on the pair structure, thermodynamics, bulk liquid-gas coexistence, and associated interfacial phenomena in many-body systems. Local learning of the one-body direct correlation functional is based on Monte Carlo simulations of inhomogeneous systems with randomized thermodynamic conditions, randomized planar shapes of the external potential, and randomized box sizes. Focusing on the prototypical Lennard-Jones system, we test predictions of the resulting neural attractive density functional across a broad spectrum of physical behavior associated with liquid-gas phase coexistence in bulk and at interfaces. We analyze the bulk radial distribution function g(r) obtained from automatic differentiation and the Ornstein-Zernike route and determine (i) the Fisher-Widom line, i.e., the crossover of the asymptotic (large distance) decay of g(r) from monotonic to oscillatory, (ii) the (Widom) line of maximal correlation length, (iii) the line of maximal isothermal compressibility, and (iv) the spinodal by calculating the poles of the structure factor in the complex plane. The bulk binodal and the density profile of the free liquid-gas interface are obtained from density functional minimization and the corresponding surface tension from functional line integration. We also show that the neural functional describes accurately the phenomena of drying at a hard wall and of capillary evaporation for a liquid confined in a slit pore. Our neural framework yields results that improve significantly upon standard mean-field treatments of interparticle attraction. Comparison with independent simulation results demonstrates a consistent picture of phase separation even when restricting the training to supercritical states only. We argue that phase coexistence and its associated signatures can be discovered as emerging phenomena via functional mappings and educated extrapolation. Published by the American Physical Society2025
{"title":"Neural Density Functional Theory of Liquid-Gas Phase Coexistence","authors":"Florian Sammüller, Matthias Schmidt, Robert Evans","doi":"10.1103/physrevx.15.011013","DOIUrl":"https://doi.org/10.1103/physrevx.15.011013","url":null,"abstract":"We use supervised machine learning together with the concepts of classical density functional theory to investigate the effects of interparticle attraction on the pair structure, thermodynamics, bulk liquid-gas coexistence, and associated interfacial phenomena in many-body systems. Local learning of the one-body direct correlation functional is based on Monte Carlo simulations of inhomogeneous systems with randomized thermodynamic conditions, randomized planar shapes of the external potential, and randomized box sizes. Focusing on the prototypical Lennard-Jones system, we test predictions of the resulting neural attractive density functional across a broad spectrum of physical behavior associated with liquid-gas phase coexistence in bulk and at interfaces. We analyze the bulk radial distribution function g</a:mi>(</a:mo>r</a:mi>)</a:mo></a:math> obtained from automatic differentiation and the Ornstein-Zernike route and determine (i) the Fisher-Widom line, i.e., the crossover of the asymptotic (large distance) decay of <e:math xmlns:e=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><e:mi>g</e:mi><e:mo stretchy=\"false\">(</e:mo><e:mi>r</e:mi><e:mo stretchy=\"false\">)</e:mo></e:math> from monotonic to oscillatory, (ii) the (Widom) line of maximal correlation length, (iii) the line of maximal isothermal compressibility, and (iv) the spinodal by calculating the poles of the structure factor in the complex plane. The bulk binodal and the density profile of the free liquid-gas interface are obtained from density functional minimization and the corresponding surface tension from functional line integration. We also show that the neural functional describes accurately the phenomena of drying at a hard wall and of capillary evaporation for a liquid confined in a slit pore. Our neural framework yields results that improve significantly upon standard mean-field treatments of interparticle attraction. Comparison with independent simulation results demonstrates a consistent picture of phase separation even when restricting the training to supercritical states only. We argue that phase coexistence and its associated signatures can be discovered as emerging phenomena via functional mappings and educated extrapolation. <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":"3 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143030930","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}
Pub Date : 2025-01-23DOI: 10.1103/physrevx.15.011012
Daniel Jost, Eder G. Lomeli, Ta Tang, Joshua J. Kas, John J. Rehr, Wei-Sheng Lee, Hong-Chen Jiang, Brian Moritz, Thomas P. Devereaux
X-ray spectroscopy has been a key method to determine ground- and excited-state properties of quantum materials with atomic specificity. Now, new x-ray facilities are opening the door to the study of pump-probe x-ray spectroscopy—specifically, time-resolved x-ray absorption (trXAS) and time-resolved resonant inelastic x-ray scattering (trRIXS). In this paper, we will present simulations of each of these spectroscopies using a time-domain full atomic multiplet, charge-transfer Hamiltonian adapted to study the properties of a generalized cluster model including a central transition-metal ion caged by ligand atoms in a planar geometry. The numerically evaluated trXAS and trRIXS cross sections for representative electron configurations 3d9 and 3d8 demonstrate the insights that can be obtained from charge-transfer pumping and how this nonequilibrium process affects ground- and excited-state properties. The straightforward characterization of the excitations in these systems based on our analysis of the simulations can serve as a benchmark for future experiments, as access to these time-resolved spectroscopic techniques becomes more widely available. Published by the American Physical Society2025
{"title":"Time-Resolved X-Ray Spectroscopy from the Atomic Orbital Ground State Up","authors":"Daniel Jost, Eder G. Lomeli, Ta Tang, Joshua J. Kas, John J. Rehr, Wei-Sheng Lee, Hong-Chen Jiang, Brian Moritz, Thomas P. Devereaux","doi":"10.1103/physrevx.15.011012","DOIUrl":"https://doi.org/10.1103/physrevx.15.011012","url":null,"abstract":"X-ray spectroscopy has been a key method to determine ground- and excited-state properties of quantum materials with atomic specificity. Now, new x-ray facilities are opening the door to the study of pump-probe x-ray spectroscopy—specifically, time-resolved x-ray absorption (trXAS) and time-resolved resonant inelastic x-ray scattering (trRIXS). In this paper, we will present simulations of each of these spectroscopies using a time-domain full atomic multiplet, charge-transfer Hamiltonian adapted to study the properties of a generalized cluster model including a central transition-metal ion caged by ligand atoms in a planar geometry. The numerically evaluated trXAS and trRIXS cross sections for representative electron configurations 3</a:mn>d</a:mi>9</a:mn></a:msup></a:math> and <c:math xmlns:c=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><c:mn>3</c:mn><c:msup><c:mi>d</c:mi><c:mn>8</c:mn></c:msup></c:math> demonstrate the insights that can be obtained from charge-transfer pumping and how this nonequilibrium process affects ground- and excited-state properties. The straightforward characterization of the excitations in these systems based on our analysis of the simulations can serve as a benchmark for future experiments, as access to these time-resolved spectroscopic techniques becomes more widely available. <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":"51 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143026598","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}
Pub Date : 2025-01-22DOI: 10.1103/physrevx.15.011011
L.-A. Sellem, A. Sarlette, Z. Leghtas, M. Mirrahimi, P. Rouchon, P. Campagne-Ibarcq
We propose a novel approach to generate, protect, and control Gottesman-Kitaev-Preskill (GKP) qubits. It employs a microwave frequency comb parametrically modulating a Josephson circuit to enforce a dissipative dynamics of a high-impedance circuit mode, autonomously stabilizing the finite-energy GKP code. The encoded GKP qubit is robustly protected against all dominant decoherence channels plaguing superconducting circuits but quasiparticle poisoning. In particular, noise from ancillary modes leveraged for dissipation engineering does not propagate at the logical level. In a state-of-the-art experimental setup, we estimate that the encoded qubit lifetime could extend 2 orders of magnitude beyond the break-even point, with substantial margin for improvement through progress in fabrication and control electronics. Qubit initialization, readout, and control via Clifford gates can be performed while maintaining the code stabilization, paving the way toward the assembly of GKP qubits in a fault-tolerant quantum computing architecture. Published by the American Physical Society2025
{"title":"Dissipative Protection of a GKP Qubit in a High-Impedance Superconducting Circuit Driven by a Microwave Frequency Comb","authors":"L.-A. Sellem, A. Sarlette, Z. Leghtas, M. Mirrahimi, P. Rouchon, P. Campagne-Ibarcq","doi":"10.1103/physrevx.15.011011","DOIUrl":"https://doi.org/10.1103/physrevx.15.011011","url":null,"abstract":"We propose a novel approach to generate, protect, and control Gottesman-Kitaev-Preskill (GKP) qubits. It employs a microwave frequency comb parametrically modulating a Josephson circuit to enforce a dissipative dynamics of a high-impedance circuit mode, autonomously stabilizing the finite-energy GKP code. The encoded GKP qubit is robustly protected against all dominant decoherence channels plaguing superconducting circuits but quasiparticle poisoning. In particular, noise from ancillary modes leveraged for dissipation engineering does not propagate at the logical level. In a state-of-the-art experimental setup, we estimate that the encoded qubit lifetime could extend 2 orders of magnitude beyond the break-even point, with substantial margin for improvement through progress in fabrication and control electronics. Qubit initialization, readout, and control via Clifford gates can be performed while maintaining the code stabilization, paving the way toward the assembly of GKP qubits in a fault-tolerant quantum computing architecture. <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":"2025-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143020436","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}
Pub Date : 2025-01-21DOI: 10.1103/physrevx.15.011010
Tobias Nadolny, Christoph Bruder, Matteo Brunelli
Active agents are capable of exerting nonreciprocal forces upon one another. For instance, one agent, say A, may attract another agent B while B repels A. These antagonistic nonreciprocal interactions have been extensively studied in classical systems, revealing a wealth of exciting phenomena such as novel phase transitions and traveling-wave states. Whether these phenomena can originate in quantum many-body systems is an open issue, and proposals for their realization are lacking. In this work, we present a model of two species of quantum spins that interact in an antagonistic nonreciprocal way of the attraction-repulsion type. We propose an implementation based on two atomic ensembles coupled via chiral waveguides featuring both braided and nonbraided geometries. The spins are active due to the presence of local gain, which allows them to synchronize. In the thermodynamic limit, we show that nonreciprocal interactions result in a nonreciprocal phase transition to time-crystalline traveling-wave states, associated with spontaneous breaking of parity-time symmetry. We establish how this symmetry emerges from the microscopic quantum model. For a finite number of spins, signatures of the time-crystal phase can still be identified by inspecting equal-time or two-time correlation functions. Remarkably, continuous monitoring of the output field of the waveguides induces a quantum traveling-wave state: a time-crystalline state of a finite-size quantum system, in which parity-time symmetry is spontaneously broken. Our work lays the foundation to explore nonreciprocal interactions in active quantum matter. Published by the American Physical Society2025
{"title":"Nonreciprocal Synchronization of Active Quantum Spins","authors":"Tobias Nadolny, Christoph Bruder, Matteo Brunelli","doi":"10.1103/physrevx.15.011010","DOIUrl":"https://doi.org/10.1103/physrevx.15.011010","url":null,"abstract":"Active agents are capable of exerting nonreciprocal forces upon one another. For instance, one agent, say A</a:mi></a:math>, may attract another agent <c:math xmlns:c=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><c:mi>B</c:mi></c:math> while <e:math xmlns:e=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><e:mi>B</e:mi></e:math> repels <g:math xmlns:g=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><g:mi>A</g:mi></g:math>. These antagonistic nonreciprocal interactions have been extensively studied in classical systems, revealing a wealth of exciting phenomena such as novel phase transitions and traveling-wave states. Whether these phenomena can originate in quantum many-body systems is an open issue, and proposals for their realization are lacking. In this work, we present a model of two species of quantum spins that interact in an antagonistic nonreciprocal way of the attraction-repulsion type. We propose an implementation based on two atomic ensembles coupled via chiral waveguides featuring both braided and nonbraided geometries. The spins are active due to the presence of local gain, which allows them to synchronize. In the thermodynamic limit, we show that nonreciprocal interactions result in a nonreciprocal phase transition to time-crystalline traveling-wave states, associated with spontaneous breaking of parity-time symmetry. We establish how this symmetry emerges from the microscopic quantum model. For a finite number of spins, signatures of the time-crystal phase can still be identified by inspecting equal-time or two-time correlation functions. Remarkably, continuous monitoring of the output field of the waveguides induces a quantum traveling-wave state: a time-crystalline state of a finite-size quantum system, in which parity-time symmetry is spontaneously broken. Our work lays the foundation to explore nonreciprocal interactions in active quantum matter. <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":"74 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142992201","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}
Pub Date : 2025-01-17DOI: 10.1103/physrevx.15.011009
Michael Peper, Yiyi Li, Daniel Y. Knapp, Mila Bileska, Shuo Ma, Genyue Liu, Pai Peng, Bichen Zhang, Sebastian P. Horvath, Alex P. Burgers, Jeff D. Thompson
Highly excited Rydberg states and their interactions play an important role in quantum computing and simulation. These properties can be predicted accurately for alkali atoms with simple Rydberg level structures. However, an extension of these methods to more complex atoms such as alkaline-earth atoms has not been demonstrated or experimentally validated. Here, we present multichannel quantum defect models for highly excited Yb174 and Yb171 Rydberg states with L≤2. The models are developed using a combination of existing literature data and new, high-precision laser and microwave spectroscopy in an atomic beam, and validated by detailed comparison with experimentally measured Stark shifts and magnetic moments. We then use these models to compute interaction potentials between two Yb atoms, and find excellent agreement with direct measurements in an optical tweezer array. From the computed interaction potential, we identify an anomalous Förster resonance that likely degraded the fidelity of previous entangling gates in Yb171 using F=3/2 Rydberg states. We then identify a more suitable F=1/2 state, and achieve a state-of-the-art controlled- gate fidelity of F=0.994(1), with the remaining error fully explained by known sources. This work establishes a solid foundation for the continued development of quantum computing, simulation, and entanglement-enhanced metrology with Yb neutral atom arrays. Published by the American Physical Society2025
{"title":"Spectroscopy and Modeling of Yb171 Rydberg States for High-Fidelity Two-Qubit Gates","authors":"Michael Peper, Yiyi Li, Daniel Y. Knapp, Mila Bileska, Shuo Ma, Genyue Liu, Pai Peng, Bichen Zhang, Sebastian P. Horvath, Alex P. Burgers, Jeff D. Thompson","doi":"10.1103/physrevx.15.011009","DOIUrl":"https://doi.org/10.1103/physrevx.15.011009","url":null,"abstract":"Highly excited Rydberg states and their interactions play an important role in quantum computing and simulation. These properties can be predicted accurately for alkali atoms with simple Rydberg level structures. However, an extension of these methods to more complex atoms such as alkaline-earth atoms has not been demonstrated or experimentally validated. Here, we present multichannel quantum defect models for highly excited Yb</a:mi></a:mrow>174</a:mn></a:mrow></a:mmultiscripts></a:mrow></a:math> and <c:math xmlns:c=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><c:mrow><c:mmultiscripts><c:mrow><c:mi>Yb</c:mi></c:mrow><c:mprescripts/><c:none/><c:mrow><c:mn>171</c:mn></c:mrow></c:mmultiscripts></c:mrow></c:math> Rydberg states with <e:math xmlns:e=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><e:mi>L</e:mi><e:mo>≤</e:mo><e:mn>2</e:mn></e:math>. The models are developed using a combination of existing literature data and new, high-precision laser and microwave spectroscopy in an atomic beam, and validated by detailed comparison with experimentally measured Stark shifts and magnetic moments. We then use these models to compute interaction potentials between two Yb atoms, and find excellent agreement with direct measurements in an optical tweezer array. From the computed interaction potential, we identify an anomalous Förster resonance that likely degraded the fidelity of previous entangling gates in <g:math xmlns:g=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><g:mrow><g:mmultiscripts><g:mrow><g:mi>Yb</g:mi></g:mrow><g:mprescripts/><g:none/><g:mrow><g:mn>171</g:mn></g:mrow></g:mmultiscripts></g:mrow></g:math> using <i:math xmlns:i=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><i:mi>F</i:mi><i:mo>=</i:mo><i:mn>3</i:mn><i:mo>/</i:mo><i:mn>2</i:mn></i:math> Rydberg states. We then identify a more suitable <k:math xmlns:k=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><k:mi>F</k:mi><k:mo>=</k:mo><k:mn>1</k:mn><k:mo>/</k:mo><k:mn>2</k:mn></k:math> state, and achieve a state-of-the-art controlled- gate fidelity of <m:math xmlns:m=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><m:mi mathvariant=\"script\">F</m:mi><m:mo>=</m:mo><m:mn>0.994</m:mn><m:mo stretchy=\"false\">(</m:mo><m:mn>1</m:mn><m:mo stretchy=\"false\">)</m:mo></m:math>, with the remaining error fully explained by known sources. This work establishes a solid foundation for the continued development of quantum computing, simulation, and entanglement-enhanced metrology with Yb neutral atom arrays. <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":"2 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142987818","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}
Pub Date : 2025-01-16DOI: 10.1103/physrevx.15.011008
Jun Wang, Taran Driver, Paris L. Franz, Přemysl Kolorenč, Emily Thierstein, River R. Robles, Erik Isele, Zhaoheng Guo, David Cesar, Oliver Alexander, Sandra Beauvarlet, Kurtis Borne, Xinxin Cheng, Louis F. DiMauro, Joseph Duris, James M. Glownia, Martin Graßl, Paul Hockett, Matthias Hoffman, Andrei Kamalov, Kirk A. Larsen, Siqi Li, Xiang Li, Ming-Fu Lin, Razib Obaid, Philipp Rosenberger, Peter Walter, Thomas J. A. Wolf, Jon P. Marangos, Matthias F. Kling, Philip H. Bucksbaum, Agostino Marinelli, James P. Cryan
The detailed understanding of electronic coherence in quantum systems requires measurements on the attosecond timescale. Attosecond x-ray pulses enable the study of electronic coherence in core-excited molecular systems. Here we report on the coherent motion of electrons in the 1,1-difluoroethylene ion following ionization of the K shell of the two nonequivalent carbon sites with a subfemtosecond x-ray pulse. Using the angular streaking technique to track the Auger-Meitner decay, we observe temporal modulations of the emission, indicating the electronic coherence of the core-excited ionic states, and extract a 6.5±0.8fs average lifetime of the core-level vacancies. A quantum-mechanical model is employed to interpret the measurement, and we find the observed temporal modulations are independent of charge density oscillations. This work opens a new regime of coherent electronic motion, beyond charge migration, where electronic coherence manifests in the nonlocal quantum correlation between atomic sites while charge density oscillation is absent. Our results broaden the landscape of electronic coherence in molecular systems. Published by the American Physical Society2025
{"title":"Probing Electronic Coherence between Core-Level Vacancies at Different Atomic Sites","authors":"Jun Wang, Taran Driver, Paris L. Franz, Přemysl Kolorenč, Emily Thierstein, River R. Robles, Erik Isele, Zhaoheng Guo, David Cesar, Oliver Alexander, Sandra Beauvarlet, Kurtis Borne, Xinxin Cheng, Louis F. DiMauro, Joseph Duris, James M. Glownia, Martin Graßl, Paul Hockett, Matthias Hoffman, Andrei Kamalov, Kirk A. Larsen, Siqi Li, Xiang Li, Ming-Fu Lin, Razib Obaid, Philipp Rosenberger, Peter Walter, Thomas J. A. Wolf, Jon P. Marangos, Matthias F. Kling, Philip H. Bucksbaum, Agostino Marinelli, James P. Cryan","doi":"10.1103/physrevx.15.011008","DOIUrl":"https://doi.org/10.1103/physrevx.15.011008","url":null,"abstract":"The detailed understanding of electronic coherence in quantum systems requires measurements on the attosecond timescale. Attosecond x-ray pulses enable the study of electronic coherence in core-excited molecular systems. Here we report on the coherent motion of electrons in the 1,1-difluoroethylene ion following ionization of the K</a:mi></a:math> shell of the two nonequivalent carbon sites with a subfemtosecond x-ray pulse. Using the angular streaking technique to track the Auger-Meitner decay, we observe temporal modulations of the emission, indicating the electronic coherence of the core-excited ionic states, and extract a <c:math xmlns:c=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><c:mn>6.5</c:mn><c:mo>±</c:mo><c:mn>0.8</c:mn><c:mtext> </c:mtext><c:mtext> </c:mtext><c:mi>fs</c:mi></c:math> average lifetime of the core-level vacancies. A quantum-mechanical model is employed to interpret the measurement, and we find the observed temporal modulations are independent of charge density oscillations. This work opens a new regime of coherent electronic motion, beyond charge migration, where electronic coherence manifests in the nonlocal quantum correlation between atomic sites while charge density oscillation is absent. Our results broaden the landscape of electronic coherence in molecular systems. <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":"45 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142988066","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}
Pub Date : 2025-01-15DOI: 10.1103/physrevx.15.011007
Noah Schnitzer, Berit H. Goodge, Gregory Powers, Jaewook Kim, Sang-Wook Cheong, Ismail El Baggari, Lena F. Kourkoutis
Charge order pervades the phase diagrams of quantum materials where it competes with superconducting and magnetic phases, hosts electronic phase transitions and topological defects, and couples to the lattice generating intricate structural distortions. Incommensurate charge order is readily stabilized in manganese oxides, where it is associated with anomalous electronic and magnetic properties, but its nanoscale structural inhomogeneity complicates precise characterization and understanding of its relationship with competing phases. Leveraging atomic-resolution variable-temperature cryogenic scanning transmission electron microscopy, we characterize the thermal evolution of charge order as it transforms from its ground state in a model manganite system. We find that mobile networks of discommensurations and dislocations generate phase inhomogeneity and induce global incommensurability in an otherwise lattice-locked modulation. Driving the order to melt at high temperatures, the discommensuration density grows, and regions of order locally decouple from the lattice periodicity. Published by the American Physical Society2025
{"title":"Atomic-Scale Tracking of Topological Defect Motion and Incommensurate Charge Order Melting","authors":"Noah Schnitzer, Berit H. Goodge, Gregory Powers, Jaewook Kim, Sang-Wook Cheong, Ismail El Baggari, Lena F. Kourkoutis","doi":"10.1103/physrevx.15.011007","DOIUrl":"https://doi.org/10.1103/physrevx.15.011007","url":null,"abstract":"Charge order pervades the phase diagrams of quantum materials where it competes with superconducting and magnetic phases, hosts electronic phase transitions and topological defects, and couples to the lattice generating intricate structural distortions. Incommensurate charge order is readily stabilized in manganese oxides, where it is associated with anomalous electronic and magnetic properties, but its nanoscale structural inhomogeneity complicates precise characterization and understanding of its relationship with competing phases. Leveraging atomic-resolution variable-temperature cryogenic scanning transmission electron microscopy, we characterize the thermal evolution of charge order as it transforms from its ground state in a model manganite system. We find that mobile networks of discommensurations and dislocations generate phase inhomogeneity and induce global incommensurability in an otherwise lattice-locked modulation. Driving the order to melt at high temperatures, the discommensuration density grows, and regions of order locally decouple from the lattice periodicity. <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":"53 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142986639","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}
Pub Date : 2025-01-14DOI: 10.1103/physrevx.15.011006
Yishuai Wang, Siyuan Hong, Wenze Pan, Yi Zhou, Yanwu Xie
The extremely low superfluid density and unprecedented tunability of oxide interface superconductors provide an ideal platform for studying fluctuations in two-dimensional superconductors. In this work, we fabricate an LaAlO3/KTaO3 interface superconductor patterned with a nanohoneycomb array of insulating islands. Little-Parks-like magnetoresistance oscillations are observed, which are dictated by the superconducting flux quantum h/2e. Moreover, an anomalous negative magnetoresistance (ANMR) appears under a weak magnetic field, suggesting magnetic-field-enhanced superconductivity. By examining their dependences on temperature, measurement current, and electrical gating, we conclude that both phenomena are associated with superconducting order parameter: The h/2e oscillations provide direct evidence of Cooper-pair transport, and the ANMR is interpreted as a consequence of multiple connected narrow superconducting paths with strong fluctuations. Published by the American Physical Society2025
{"title":"Superconducting Quantum Oscillations and Anomalous Negative Magnetoresistance in a Honeycomb Nanopatterned Oxide Interface Superconductor","authors":"Yishuai Wang, Siyuan Hong, Wenze Pan, Yi Zhou, Yanwu Xie","doi":"10.1103/physrevx.15.011006","DOIUrl":"https://doi.org/10.1103/physrevx.15.011006","url":null,"abstract":"The extremely low superfluid density and unprecedented tunability of oxide interface superconductors provide an ideal platform for studying fluctuations in two-dimensional superconductors. In this work, we fabricate an LaAlO</a:mi></a:mrow>3</a:mn></a:msub>/</a:mo>KTaO</a:mi></a:mrow>3</a:mn></a:msub></a:mrow></a:math> interface superconductor patterned with a nanohoneycomb array of insulating islands. Little-Parks-like magnetoresistance oscillations are observed, which are dictated by the superconducting flux quantum <d:math xmlns:d=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><d:mrow><d:mi>h</d:mi><d:mo stretchy=\"false\">/</d:mo><d:mn>2</d:mn><d:mi>e</d:mi></d:mrow></d:math>. Moreover, an anomalous negative magnetoresistance (ANMR) appears under a weak magnetic field, suggesting magnetic-field-enhanced superconductivity. By examining their dependences on temperature, measurement current, and electrical gating, we conclude that both phenomena are associated with superconducting order parameter: The <g:math xmlns:g=\"http://www.w3.org/1998/Math/MathML\" display=\"inline\"><g:mrow><g:mi>h</g:mi><g:mo stretchy=\"false\">/</g:mo><g:mn>2</g:mn><g:mi>e</g:mi></g:mrow></g:math> oscillations provide direct evidence of Cooper-pair transport, and the ANMR is interpreted as a consequence of multiple connected narrow superconducting paths with strong fluctuations. <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":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142981538","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}
Pub Date : 2025-01-13DOI: 10.1103/physrevx.15.011004
Valentin Crépel, Jennifer Cano
Two-dimensional materials subject to long-wavelength modulations have emerged as novel platforms to study topological and correlated quantum phases. In this article, we develop a versatile and computationally inexpensive method to predict the topological properties of materials subjected to a superlattice potential by combining degenerate perturbation theory with the method of symmetry indicators. In the absence of electronic interactions, our analysis provides a systematic rule to find the Chern number of the superlattice-induced miniband starting from the harmonics of the applied potential and a few material-specific coefficients. Our method also applies to anomalous (interaction-generated) bands, for which we derive an efficient algorithm to determine all Chern numbers compatible with a self-consistent solution to the Hartree-Fock equations. Our approach gives a microscopic understanding of the quantum anomalous Hall insulators recently observed in rhombohedral graphene multilayers. Published by the American Physical Society2025
{"title":"Efficient Prediction of Superlattice and Anomalous Miniband Topology from Quantum Geometry","authors":"Valentin Crépel, Jennifer Cano","doi":"10.1103/physrevx.15.011004","DOIUrl":"https://doi.org/10.1103/physrevx.15.011004","url":null,"abstract":"Two-dimensional materials subject to long-wavelength modulations have emerged as novel platforms to study topological and correlated quantum phases. In this article, we develop a versatile and computationally inexpensive method to predict the topological properties of materials subjected to a superlattice potential by combining degenerate perturbation theory with the method of symmetry indicators. In the absence of electronic interactions, our analysis provides a systematic rule to find the Chern number of the superlattice-induced miniband starting from the harmonics of the applied potential and a few material-specific coefficients. Our method also applies to anomalous (interaction-generated) bands, for which we derive an efficient algorithm to determine all Chern numbers compatible with a self-consistent solution to the Hartree-Fock equations. Our approach gives a microscopic understanding of the quantum anomalous Hall insulators recently observed in rhombohedral graphene multilayers. <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":"6 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142974527","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}
Pub Date : 2025-01-13DOI: 10.1103/physrevx.15.011005
William Gilpin
Unmeasured causal forces influence diverse experimental time series, such as the transcription factors that regulate genes or the descending neurons that steer motor circuits. Combining the theory of skew-product dynamical systems with topological data analysis, we show that simultaneous recurrence events across multiple time series reveal the structure of their shared unobserved driving signal. We introduce a physics-based unsupervised learning algorithm that reconstructs causal drivers by iteratively building a recurrence graph with glasslike structure. As the amount of data increases, a percolation transition on this graph leads to weak ergodicity breaking for random walks—revealing the shared driver’s dynamics, even from strongly corrupted measurements. We relate reconstruction accuracy to the rate of information transfer from a chaotic driver to the response systems, and we find that effective reconstruction proceeds through gradual approximation of the driver’s dynamical attractor. Through extensive benchmarks against classical signal processing and machine learning techniques, we demonstrate our method’s ability to extract causal drivers from diverse experimental datasets spanning ecology, genomics, fluid dynamics, and physiology. Published by the American Physical Society2025
{"title":"Recurrences Reveal Shared Causal Drivers of Complex Time Series","authors":"William Gilpin","doi":"10.1103/physrevx.15.011005","DOIUrl":"https://doi.org/10.1103/physrevx.15.011005","url":null,"abstract":"Unmeasured causal forces influence diverse experimental time series, such as the transcription factors that regulate genes or the descending neurons that steer motor circuits. Combining the theory of skew-product dynamical systems with topological data analysis, we show that simultaneous recurrence events across multiple time series reveal the structure of their shared unobserved driving signal. We introduce a physics-based unsupervised learning algorithm that reconstructs causal drivers by iteratively building a recurrence graph with glasslike structure. As the amount of data increases, a percolation transition on this graph leads to weak ergodicity breaking for random walks—revealing the shared driver’s dynamics, even from strongly corrupted measurements. We relate reconstruction accuracy to the rate of information transfer from a chaotic driver to the response systems, and we find that effective reconstruction proceeds through gradual approximation of the driver’s dynamical attractor. Through extensive benchmarks against classical signal processing and machine learning techniques, we demonstrate our method’s ability to extract causal drivers from diverse experimental datasets spanning ecology, genomics, fluid dynamics, and physiology. <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":"6 1","pages":""},"PeriodicalIF":12.5,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142974822","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}
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