Pub Date : 2024-09-17DOI: 10.1103/physrevresearch.6.l032067
Christopher Ekman, Emil J. Bergholtz
Strongly interacting nonequilibrium systems are of great fundamental interest, yet their inherent complexity make them notoriously hard to analyze. We demonstrate that the dynamics of the Bose-Hubbard model, which by itself evades solvability, can be solved exactly at any interaction strength in the presence of loss tuned to a rate matching the hopping amplitude. Remarkably, the full solvability of the corresponding Liouvillian, and the integrability of the pertinent effective non-Hermitian Hamiltonian, survives the addition of disorder and generic boundary conditions. By analyzing the Bethe ansatz solutions we find that even weak interactions change the qualitative features of the system, leading to an intricate dynamical phase diagram featuring non-Hermitian Mott-skin effects, disorder induced localization, highly degenerate exceptional points, and a Bose glasslike phase of fragmented condensates. We discuss realistic implementations of this model with cold atoms.
{"title":"Liouvillian skin effects and fragmented condensates in an integrable dissipative Bose-Hubbard model","authors":"Christopher Ekman, Emil J. Bergholtz","doi":"10.1103/physrevresearch.6.l032067","DOIUrl":"https://doi.org/10.1103/physrevresearch.6.l032067","url":null,"abstract":"Strongly interacting nonequilibrium systems are of great fundamental interest, yet their inherent complexity make them notoriously hard to analyze. We demonstrate that the dynamics of the Bose-Hubbard model, which by itself evades solvability, can be solved exactly at any interaction strength in the presence of loss tuned to a rate matching the hopping amplitude. Remarkably, the full solvability of the corresponding Liouvillian, and the integrability of the pertinent effective non-Hermitian Hamiltonian, survives the addition of disorder and generic boundary conditions. By analyzing the Bethe ansatz solutions we find that even weak interactions change the qualitative features of the system, leading to an intricate dynamical phase diagram featuring non-Hermitian Mott-skin effects, disorder induced localization, highly degenerate exceptional points, and a Bose glasslike phase of fragmented condensates. We discuss realistic implementations of this model with cold atoms.","PeriodicalId":20546,"journal":{"name":"Physical Review Research","volume":"38 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142248811","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-17DOI: 10.1103/physrevresearch.6.033310
Hang Ren, Yipei Zhang, Ze Zheng, Cuifeng Ying, Lei Xu, Mohsen Rahmani, K. Birgitta Whaley
Estimating properties of quantum states via randomized measurements has become a significant part of quantum information science. In this paper, we design an innovative approach leveraging metasurfaces to perform randomized measurements on photonic qubits, together with error mitigation techniques that suppress realistic metasurface measurement noise. Through fidelity and purity estimation, we confirm the capability of metasurfaces to implement randomized measurements and the unbiased nature of our error-mitigated estimator. Our findings show the potential of metasurface-based randomized measurement schemes in achieving robust and resource-efficient estimation of quantum state properties.
{"title":"Error mitigated metasurface-based randomized measurement schemes","authors":"Hang Ren, Yipei Zhang, Ze Zheng, Cuifeng Ying, Lei Xu, Mohsen Rahmani, K. Birgitta Whaley","doi":"10.1103/physrevresearch.6.033310","DOIUrl":"https://doi.org/10.1103/physrevresearch.6.033310","url":null,"abstract":"Estimating properties of quantum states via randomized measurements has become a significant part of quantum information science. In this paper, we design an innovative approach leveraging metasurfaces to perform randomized measurements on photonic qubits, together with error mitigation techniques that suppress realistic metasurface measurement noise. Through fidelity and purity estimation, we confirm the capability of metasurfaces to implement randomized measurements and the unbiased nature of our error-mitigated estimator. Our findings show the potential of metasurface-based randomized measurement schemes in achieving robust and resource-efficient estimation of quantum state properties.","PeriodicalId":20546,"journal":{"name":"Physical Review Research","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142248877","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-17DOI: 10.1103/physrevresearch.6.033308
Ralph Sabbagh, Olga Movilla Miangolarra, Tryphon T. Georgiou
Physical systems transition between states with finite speed that is limited by energetic costs. In this work, we derive bounds on transition times for general Langevin systems that admit a decomposition into reversible and irreversible dynamics, in terms of the Wasserstein distance between states and the energetic costs associated with respective reversible and irreversible currents. For illustration we discuss Brownian particles subject to arbitrary forcing and an RLC circuit with time-varying inductor.
{"title":"Wasserstein speed limits for Langevin systems","authors":"Ralph Sabbagh, Olga Movilla Miangolarra, Tryphon T. Georgiou","doi":"10.1103/physrevresearch.6.033308","DOIUrl":"https://doi.org/10.1103/physrevresearch.6.033308","url":null,"abstract":"Physical systems transition between states with finite speed that is limited by energetic costs. In this work, we derive bounds on transition times for general Langevin systems that admit a decomposition into reversible and irreversible dynamics, in terms of the Wasserstein distance between states and the energetic costs associated with respective reversible and irreversible currents. For illustration we discuss Brownian particles subject to arbitrary forcing and an RLC circuit with time-varying inductor.","PeriodicalId":20546,"journal":{"name":"Physical Review Research","volume":"116 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142248816","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-17DOI: 10.1103/physrevresearch.6.033309
Sergiy Zhuk, Niall F. Robertson, Sergey Bravyi
Multi-product formulas (MPFs) are linear combinations of Trotter circuits offering high-quality simulation of Hamiltonian time evolution with fewer Trotter steps. Here we report two contributions aimed at making multi-product formulas more viable for near-term quantum simulations. First, we extend the theory of Trotter error with commutator scaling developed by Childs et al. [A. M. Childs et al., Phys. Rev. X11, 011020 (2021)] to multi-product formulas. Our result implies that multi-product formulas can achieve a quadratic reduction of Trotter error in 1-norm (nuclear norm) on arbitrary time intervals compared with the regular product formulas without increasing the required circuit depth or qubit connectivity. The number of circuit repetitions grows only by a constant factor. Second, we introduce dynamic multi-product formulas with time-dependent coefficients chosen to minimize a certain efficiently computable proxy for the Trotter error. We use a minimax estimation method to make dynamic multi-product formulas robust to uncertainty from algorithmic errors, sampling, and hardware noise. We call this method the minimax MPF and we provide a rigorous bound on its error.
多乘积公式（MPF）是特罗特电路的线性组合，能以较少的特罗特步骤高质量地模拟哈密尔顿时间演化。我们在此报告两项贡献，旨在使多积公式在近期量子模拟中更加可行。首先，我们将 Childs 等人[A. M. Childs 等人，Phys. Rev. X 11, 011020 (2021)]开发的具有换向器缩放的特罗特误差理论扩展到多乘积公式。我们的结果意味着，与常规乘积公式相比，多乘积公式可以在任意时间间隔上实现 1-正态（核正态）特罗特误差的四次方减少，而无需增加所需的电路深度或量子比特连接性。电路重复次数只增加一个常数因子。其次，我们引入了动态多乘积公式，并选择了随时间变化的系数，以最小化某种可有效计算的特罗特误差代理。我们采用最小估计法，使动态多乘法公式对算法误差、采样和硬件噪声带来的不确定性具有鲁棒性。我们称这种方法为 minimax MPF，并为其误差提供了严格的约束。
{"title":"Trotter error bounds and dynamic multi-product formulas for Hamiltonian simulation","authors":"Sergiy Zhuk, Niall F. Robertson, Sergey Bravyi","doi":"10.1103/physrevresearch.6.033309","DOIUrl":"https://doi.org/10.1103/physrevresearch.6.033309","url":null,"abstract":"Multi-product formulas (MPFs) are linear combinations of Trotter circuits offering high-quality simulation of Hamiltonian time evolution with fewer Trotter steps. Here we report two contributions aimed at making multi-product formulas more viable for near-term quantum simulations. First, we extend the theory of Trotter error with commutator scaling developed by Childs <i>et al.</i> [A. M. Childs <i>et al.</i>, <span>Phys. Rev. X</span> <b>11</b>, 011020 (2021)] to multi-product formulas. Our result implies that multi-product formulas can achieve a quadratic reduction of Trotter error in 1-norm (nuclear norm) on arbitrary time intervals compared with the regular product formulas without increasing the required circuit depth or qubit connectivity. The number of circuit repetitions grows only by a constant factor. Second, we introduce dynamic multi-product formulas with time-dependent coefficients chosen to minimize a certain efficiently computable proxy for the Trotter error. We use a minimax estimation method to make dynamic multi-product formulas robust to uncertainty from algorithmic errors, sampling, and hardware noise. We call this method the minimax MPF and we provide a rigorous bound on its error.","PeriodicalId":20546,"journal":{"name":"Physical Review Research","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142248685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-16DOI: 10.1103/physrevresearch.6.l032065
M. Ahmadiet al.(The ALPHA Collaboration)
Magnetically trapped antihydrogen atoms can be cooled by expanding the volume of the trap in which they are confined. We report a proof-of-principle experiment in which antiatoms are deliberately released from expanded and static traps. Antiatoms escape at an average trap depth of (statistical errors only) from the expanded trap while they escape at average depths of and from two different static traps. (We employ temperature-equivalent energy units.) Detailed simulations qualitatively agree with the escape times measured in the experiment and show a decrease of (statistical ) in the mean energy of the population after the trap expansion without significantly increasing antiatom loss compared to typical static confinement protocols. This change is bracketed by the predictions of one-dimensional and three-dimensional semianalytic adiabatic expansion models. These experimental, simulational, and model results are consistent with obtaining an adiabatically cooled population of antihydrogen atoms that partially exchanged energy between axial and transverse degrees of freedom during the trap expansion. This result is important for future antihydrogen gravitational experiments which rely on adiabatic cooling, and it will enable antihydrogen cooling beyond the fundamental limits of laser cooling.
{"title":"Adiabatic expansion cooling of antihydrogen","authors":"M. Ahmadiet al.(The ALPHA Collaboration)","doi":"10.1103/physrevresearch.6.l032065","DOIUrl":"https://doi.org/10.1103/physrevresearch.6.l032065","url":null,"abstract":"Magnetically trapped antihydrogen atoms can be cooled by expanding the volume of the trap in which they are confined. We report a proof-of-principle experiment in which antiatoms are deliberately released from expanded and static traps. Antiatoms escape at an average trap depth of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>0.08</mn><mo>±</mo><mn>0.01</mn><mspace width=\"0.28em\"></mspace><mi mathvariant=\"normal\">K</mi></mrow></math> (statistical errors only) from the expanded trap while they escape at average depths of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>0.22</mn><mo>±</mo><mn>0.01</mn></mrow></math> and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>0.17</mn><mo>±</mo><mn>0.01</mn><mspace width=\"0.28em\"></mspace><mi mathvariant=\"normal\">K</mi></mrow></math> from two different static traps. (We employ temperature-equivalent energy units.) Detailed simulations qualitatively agree with the escape times measured in the experiment and show a decrease of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>38</mn><mo>%</mo></mrow></math> (statistical <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mtext>error</mtext><mo><</mo><mn>0.2</mn><mo>%</mo></mrow></math>) in the mean energy of the population after the trap expansion without significantly increasing antiatom loss compared to typical static confinement protocols. This change is bracketed by the predictions of one-dimensional and three-dimensional semianalytic adiabatic expansion models. These experimental, simulational, and model results are consistent with obtaining an adiabatically cooled population of antihydrogen atoms that partially exchanged energy between axial and transverse degrees of freedom during the trap expansion. This result is important for future antihydrogen gravitational experiments which rely on adiabatic cooling, and it will enable antihydrogen cooling beyond the fundamental limits of laser cooling.","PeriodicalId":20546,"journal":{"name":"Physical Review Research","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142248863","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-16DOI: 10.1103/physrevresearch.6.033307
Sebastian Morel-Balbi, Alec Kirkley
A common method for delineating urban and suburban boundaries is to identify clusters of spatial units that are highly interconnected in a network of mobility flows, each cluster signaling a cohesive economic submarket. It is critical that the methods employed for this task are principled and free of unnecessary tunable parameters to avoid unwanted inductive biases while remaining scalable for high-resolution mobility data. Here, we systematically assess the benefits and limitations of a wide array of stochastic block models (SBMs)—a family of principled, nonparametric models for identifying clusters in networks—for regionalization with mobility data. We find that the data compression capability and relative performance of different SBM variants heavily depend on the spatial extent of the mobility network, its aggregation scale, and the method used for weighting network edges. By constructing a measure to assess the degree to which a network partition violates spatial contiguity, we find that traditional SBMs may produce substantial spatial discontiguities that require extensive postprocessing to make them suitable for regionalization. We propose a fast nonparametric agglomerative algorithm to alleviate this issue, achieving data compression close to that of unconstrained SBM models while ensuring spatial contiguity, benefiting from a deterministic optimization procedure, and being generalizable to wide range of community detection objective functions.
{"title":"Bayesian regionalization of urban mobility networks","authors":"Sebastian Morel-Balbi, Alec Kirkley","doi":"10.1103/physrevresearch.6.033307","DOIUrl":"https://doi.org/10.1103/physrevresearch.6.033307","url":null,"abstract":"A common method for delineating urban and suburban boundaries is to identify clusters of spatial units that are highly interconnected in a network of mobility flows, each cluster signaling a cohesive economic submarket. It is critical that the methods employed for this task are principled and free of unnecessary tunable parameters to avoid unwanted inductive biases while remaining scalable for high-resolution mobility data. Here, we systematically assess the benefits and limitations of a wide array of stochastic block models (SBMs)—a family of principled, nonparametric models for identifying clusters in networks—for regionalization with mobility data. We find that the data compression capability and relative performance of different SBM variants heavily depend on the spatial extent of the mobility network, its aggregation scale, and the method used for weighting network edges. By constructing a measure to assess the degree to which a network partition violates spatial contiguity, we find that traditional SBMs may produce substantial spatial discontiguities that require extensive postprocessing to make them suitable for regionalization. We propose a fast nonparametric agglomerative algorithm to alleviate this issue, achieving data compression close to that of unconstrained SBM models while ensuring spatial contiguity, benefiting from a deterministic optimization procedure, and being generalizable to wide range of community detection objective functions.","PeriodicalId":20546,"journal":{"name":"Physical Review Research","volume":"191 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142248817","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-16DOI: 10.1103/physrevresearch.6.033301
Andrea Caprotti, Joshua Morris, Borivoje Dakić
In quantum information theory, the accurate estimation of observables is pivotal for quantum information processing, playing a crucial role in computational and communication protocols. This work introduces a technique for estimating such objects, leveraging an underutilized resource in the inversion map of classical shadows that greatly refines the estimation cost of target observables without incurring any additional overhead. A generalized framework for computing and optimizing additional degrees of freedom in the homogeneous space of the shadow inversion is given that may be adapted to a variety of near-term problems. In the special case of local measurement strategies, we show feasible optimization leading to an exponential separation in sample complexity versus the standard approach and, in an exceptional case, we give nontrivial examples of optimized postprocessing for local measurements, achieving the same efficiency as the global Cliffords shadows.
{"title":"Optimizing quantum tomography via shadow inversion","authors":"Andrea Caprotti, Joshua Morris, Borivoje Dakić","doi":"10.1103/physrevresearch.6.033301","DOIUrl":"https://doi.org/10.1103/physrevresearch.6.033301","url":null,"abstract":"In quantum information theory, the accurate estimation of observables is pivotal for quantum information processing, playing a crucial role in computational and communication protocols. This work introduces a technique for estimating such objects, leveraging an underutilized resource in the inversion map of classical shadows that greatly refines the estimation cost of target observables without incurring any additional overhead. A generalized framework for computing and optimizing additional degrees of freedom in the homogeneous space of the shadow inversion is given that may be adapted to a variety of near-term problems. In the special case of local measurement strategies, we show feasible optimization leading to an exponential separation in sample complexity versus the standard approach and, in an exceptional case, we give nontrivial examples of optimized postprocessing for local measurements, achieving the same efficiency as the global Cliffords shadows.","PeriodicalId":20546,"journal":{"name":"Physical Review Research","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142248867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-16DOI: 10.1103/physrevresearch.6.033303
Shin-ichi Shamoto, Hiroki Yamauchi, Kazuki Iida, Kazuhiko Ikeuchi, Koji Kaneko, Yu-Sheng Chen, Shin-ichiro Yano, Pai-Tse Hsu, Min Kai Lee, Amelia Elisabeth Hall, Geetha Balakrishnan, Lieh-Jeng Chang
In a paramagnetic state of a hyperkagome lattice antiferromagnet , magnetic diffuse scattering by magnetic short-range order is observed over a wide temperature range of approximately 500 K above the Néel temperature of 190 K. We have studied the magnetic excitation with a single crystal in a wide energy range from 0.3 to 140 meV by inelastic neutron scattering, where the prominent inelastic neutron-scattering signal is observed at . The inelastic scattering intensity integrated for two of twelve magnon modes leads to a localized magnetic moment of about 5 per Mn site, although the long-range ordered magnetic moment is only 2.61 at 4 K. The result suggests that a large part of the magnetic moment does not order in , possibly due to the geometrical spin frustration of the hyperkagome lattice.
{"title":"Magnetic excitation in the hyperkagome antiferromagnet Mn3RhSi","authors":"Shin-ichi Shamoto, Hiroki Yamauchi, Kazuki Iida, Kazuhiko Ikeuchi, Koji Kaneko, Yu-Sheng Chen, Shin-ichiro Yano, Pai-Tse Hsu, Min Kai Lee, Amelia Elisabeth Hall, Geetha Balakrishnan, Lieh-Jeng Chang","doi":"10.1103/physrevresearch.6.033303","DOIUrl":"https://doi.org/10.1103/physrevresearch.6.033303","url":null,"abstract":"In a paramagnetic state of a hyperkagome lattice antiferromagnet <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Mn</mi><mn>3</mn></msub><mi>RhSi</mi></mrow></math>, magnetic diffuse scattering by magnetic short-range order is observed over a wide temperature range of approximately 500 K above the Néel temperature of 190 K. We have studied the magnetic excitation with a single crystal in a wide energy range from 0.3 to 140 meV by inelastic neutron scattering, where the prominent inelastic neutron-scattering signal is observed at <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"bold\">Q</mi><mo>=</mo><mo>(</mo><mn>2</mn><mo>,</mo><mn>0</mn><mo>,</mo><mn>0</mn><mo>)</mo></mrow></math>. The inelastic scattering intensity integrated for two of twelve magnon modes leads to a localized magnetic moment of about 5 <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>μ</mi><mi mathvariant=\"normal\">B</mi></msub></math> per Mn site, although the long-range ordered magnetic moment is only 2.61 <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>μ</mi><mi mathvariant=\"normal\">B</mi></msub></math> at 4 K. The result suggests that a large part of the magnetic moment does not order in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Mn</mi><mn>3</mn></msub><mi>RhSi</mi></mrow></math>, possibly due to the geometrical spin frustration of the hyperkagome lattice.","PeriodicalId":20546,"journal":{"name":"Physical Review Research","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142248865","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-16DOI: 10.1103/physrevresearch.6.033299
Denise S. Christovam, Martin Sundermann, Andrea Marino, Daisuke Takegami, Johannes Falke, Paulius Dolmantas, Manuel Harder, Hlynur Gretarsson, Bernhard Keimer, Andrei Gloskovskii, Maurits W. Haverkort, Ilya Elfimov, Gertrud Zwicknagl, Alexander V. Andreev, Ladislav Havela, Mitchell M. Bordelon, Eric D. Bauer, Priscila F. S. Rosa, Andrea Severing, Liu Hao Tjeng
We investigate the topological superconductor candidate using high-resolution valence-band resonant inelastic x-ray scattering at the U edges. We observe atomiclike low-energy excitations that support the correlated nature of this unconventional superconductor. These excitations originate from the U configuration, which is unexpected since the short Te2-Te2 distances exclude Te2 being . By utilizing the photoionization cross-section dependence of the photoemission spectra in combination with band structure calculations, we infer that the stabilization of the U configuration is due to the U bonding states in the U dimers acting as a charge reservoir. Our results emphasize that the description of the physical properties should commence with a ansatz.
我们利用 U M4,5 边缘的高分辨率价带共振非弹性 X 射线散射研究了拓扑超导体候选物质 UTe2。我们观察到类似原子的低能激发，支持这种非常规超导体的相关性质。这些激发源于 U 5f2 构型，这出乎我们的意料，因为 Te2-Te2 的短距离排除了 Te2 是 2-的可能性。通过利用光发射光谱的光离子化截面依赖性并结合带状结构计算，我们推断出 U 5f2 构型的稳定是由于 U 二聚体中的 U 6d 键合态充当了电荷库。我们的研究结果强调，对物理特性的描述应从 5f2 定式开始。
{"title":"Stabilization of U 5f2 configuration in UTe2 through U 6d dimers in the presence of Te2 chains","authors":"Denise S. Christovam, Martin Sundermann, Andrea Marino, Daisuke Takegami, Johannes Falke, Paulius Dolmantas, Manuel Harder, Hlynur Gretarsson, Bernhard Keimer, Andrei Gloskovskii, Maurits W. Haverkort, Ilya Elfimov, Gertrud Zwicknagl, Alexander V. Andreev, Ladislav Havela, Mitchell M. Bordelon, Eric D. Bauer, Priscila F. S. Rosa, Andrea Severing, Liu Hao Tjeng","doi":"10.1103/physrevresearch.6.033299","DOIUrl":"https://doi.org/10.1103/physrevresearch.6.033299","url":null,"abstract":"We investigate the topological superconductor candidate <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>UTe</mi><mn>2</mn></msub></math> using high-resolution valence-band resonant inelastic x-ray scattering at the U <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>M</mi><mrow><mn>4</mn><mo>,</mo><mn>5</mn></mrow></msub></math> edges. We observe atomiclike low-energy excitations that support the correlated nature of this unconventional superconductor. These excitations originate from the U <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>5</mn><msup><mi>f</mi><mn>2</mn></msup></mrow></math> configuration, which is unexpected since the short Te2-Te2 distances exclude Te2 being <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mn>2</mn><mo>−</mo></math>. By utilizing the photoionization cross-section dependence of the photoemission spectra in combination with band structure calculations, we infer that the stabilization of the U <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>5</mn><msup><mi>f</mi><mn>2</mn></msup></mrow></math> configuration is due to the U <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>6</mn><mi>d</mi></mrow></math> bonding states in the U dimers acting as a charge reservoir. Our results emphasize that the description of the physical properties should commence with a <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>5</mn><msup><mi>f</mi><mn>2</mn></msup></mrow></math> ansatz.","PeriodicalId":20546,"journal":{"name":"Physical Review Research","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142248868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-16DOI: 10.1103/physrevresearch.6.033305
Krongtum Sankaewtong, John J. Molina, Ryoichi Yamamoto
The vision of deploying miniature vehicles within the human body for intricate tasks holds tremendous promise across engineering and medical domains. Herein, optimal navigation of a cargo-towing swimmer under an applied zig-zag flow is studied by employing direct numerical simulations coupled with a deep reinforcement learning algorithm. Tasks include navigation in flow and shear-gradient directions. We initially explore combinations of state inputs, finding that optimal navigation necessitates swimmers to perceive hydrodynamics and alignment, surpassing reliance solely on hydrodynamic signals while considering their memories. Next, we study combinations of action spaces, allowing dynamic changes in swimming and/or rotational velocities by tuning and parameters of the squirmer model, respectively. By keeping both parameters fixed, cargo-towing swimmers demonstrate superior performance in the flow direction compared to swimmers without load due to tumbling movements influenced by shear flow. In the shear-gradient direction, swimmers without load outperform cargo-towing swimmers, with performance decreasing as load length increases. Across the combination of allowing and to change, the policies from solely dynamic actions demonstrate superior navigation. The policies are then used as a showcase against naive cargo-towing and inert colloidal chains. A t-distributed stochastic neighbor embedding analysis reveals the complex interplay between perceived hydrodynamic signals and swimmer position. In the flow direction, swimmers align effectively with regions of maximum velocity, while in the shear-gradient direction, periodic transitions from minimum to maximum state values occur. Comparing pullers, pushers, and neutral swimmers, cargo-towing swimmers show a reversal in swimming velocity trends, with pullers outpacing neutral and pusher swimmers, irrespective of load lengths.
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