Pub Date : 2024-09-06DOI: 10.1088/1367-2630/ad7529
Hui Liu, Zhanpeng Lu, Xu Xia, Zhihao Xu
We investigate the influence of quasiperiodic modulations on one-dimensional non-Hermitian diamond lattices with an artificial magnetic flux θ that possess flat bands. Our study shows that the symmetry of these modulations and the magnetic flux θ play a pivotal role in shaping the localization properties of the system. When θ = 0, the non-Hermitian lattice exhibits a single flat band in the crystalline case, and symmetric as well as antisymmetric modulations can induce accurate mobility edges. In contrast, when θ=π, the clean diamond lattice manifests three dispersionless bands referred to as an ‘all-band-flat’ (ABF) structure, irrespective of the non-Hermitian parameter. The ABF structure restricts the transition from delocalized to localized states, as all states remain localized for any finite symmetric modulation. Our numerical calculations further unveil that the ABF system subjected to antisymmetric modulations exhibits multifractal-to-localized edges. Multifractal states are predominantly concentrated in the internal region of the spectrum. Additionally, we explore the case where θ lies within the range of (0,π), revealing a diverse array of complex localization features. Finally, we propose a classical electrical circuit scheme to realize the non-Hermitian flat-band chain with quasiperiodic modulations.
{"title":"Fate of localization features in a one-dimensional non-Hermitian flat-band lattice with quasiperiodic modulations","authors":"Hui Liu, Zhanpeng Lu, Xu Xia, Zhihao Xu","doi":"10.1088/1367-2630/ad7529","DOIUrl":"https://doi.org/10.1088/1367-2630/ad7529","url":null,"abstract":"We investigate the influence of quasiperiodic modulations on one-dimensional non-Hermitian diamond lattices with an artificial magnetic flux <italic toggle=\"yes\">θ</italic> that possess flat bands. Our study shows that the symmetry of these modulations and the magnetic flux <italic toggle=\"yes\">θ</italic> play a pivotal role in shaping the localization properties of the system. When <italic toggle=\"yes\">θ</italic> = 0, the non-Hermitian lattice exhibits a single flat band in the crystalline case, and symmetric as well as antisymmetric modulations can induce accurate mobility edges. In contrast, when <inline-formula>\u0000<tex-math><?CDATA $theta = pi$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:mi>θ</mml:mi><mml:mo>=</mml:mo><mml:mi>π</mml:mi></mml:mrow></mml:math><inline-graphic xlink:href=\"njpad7529ieqn1.gif\"></inline-graphic></inline-formula>, the clean diamond lattice manifests three dispersionless bands referred to as an ‘all-band-flat’ (ABF) structure, irrespective of the non-Hermitian parameter. The ABF structure restricts the transition from delocalized to localized states, as all states remain localized for any finite symmetric modulation. Our numerical calculations further unveil that the ABF system subjected to antisymmetric modulations exhibits multifractal-to-localized edges. Multifractal states are predominantly concentrated in the internal region of the spectrum. Additionally, we explore the case where <italic toggle=\"yes\">θ</italic> lies within the range of <inline-formula>\u0000<tex-math><?CDATA $(0, pi)$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:mo stretchy=\"false\">(</mml:mo><mml:mn>0</mml:mn><mml:mo>,</mml:mo><mml:mi>π</mml:mi><mml:mo stretchy=\"false\">)</mml:mo></mml:mrow></mml:math><inline-graphic xlink:href=\"njpad7529ieqn2.gif\"></inline-graphic></inline-formula>, revealing a diverse array of complex localization features. Finally, we propose a classical electrical circuit scheme to realize the non-Hermitian flat-band chain with quasiperiodic modulations.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"5 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142214495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-06DOI: 10.1088/1367-2630/ad7494
Nan Zhou, Yue Sun, Ivan S Veshchunov, S Kittaka, X L Shen, H M Ma, W Wei, Y Q Pan, M Cheng, Y F Zhang, Y Kono, Yuping Sun, T Tamegai, Xuan Luo, Zhixiang Shi, Toshiro Sakakibara
The interplay between superconductivity and magnetism is an important subject in condensed matter physics. EuFe2As2-based iron pnictides could offer an interesting plateau to study their relationship that has attracted considerable attention. So far, two magnetic phase transitions were observed in EuFe2As2-based crystal, which were deemed to originate from the itinerant Fe moments (~190 K) and the localized Eu2+ moments (~19 K), respectively. Here, we systematically studied the heat capacity for the EuFe2(As1−xPx)2 crystals with x = 0.21 (optimally doped) and x = 0.29 (overdoped). We have found two new magnetic orders in the superconducting state (ranging from 0.4 to 1.2 K) in the optimally doped crystal. As more P was introduced into the As site, one of the magnetic orders becomes absent in the overdoped crystal. Additionally, we observed strong field and orientation dependence in heat capacity. The present findings in EuFe2(As1−xPx)2 have detected the new low-temperature magnetic orders, which may originate from the localized Eu2+ spins order or the spin reorientation.
超导性与磁性之间的相互作用是凝聚态物理学的一个重要课题。基于 EuFe2As2 的铁锑化物为研究它们之间的关系提供了一个有趣的平台，引起了广泛关注。迄今为止，人们在 EuFe2As2 基晶体中观察到了两种磁性相变，认为它们分别源于流动铁矩（~190 K）和局部 Eu2+ 矩（~19 K）。在这里，我们系统地研究了 x = 0.21（最佳掺杂）和 x = 0.29（过度掺杂）的 EuFe2(As1-xPx)2 晶体的热容量。我们在最佳掺杂晶体的超导态（0.4 至 1.2 K）中发现了两个新的磁阶。随着更多的 P 被引入 As 位点，其中一个磁序在过掺杂晶体中变得不存在。此外，我们还观察到热容量具有很强的磁场和取向依赖性。目前在 EuFe2(As1-xPx)2 中的发现检测到了新的低温磁序，这可能源于局部 Eu2+ 自旋序或自旋重新定向。
{"title":"Multiple magnetic orders discovered in the superconducting state of EuFe2(As 1−x P x)2","authors":"Nan Zhou, Yue Sun, Ivan S Veshchunov, S Kittaka, X L Shen, H M Ma, W Wei, Y Q Pan, M Cheng, Y F Zhang, Y Kono, Yuping Sun, T Tamegai, Xuan Luo, Zhixiang Shi, Toshiro Sakakibara","doi":"10.1088/1367-2630/ad7494","DOIUrl":"https://doi.org/10.1088/1367-2630/ad7494","url":null,"abstract":"The interplay between superconductivity and magnetism is an important subject in condensed matter physics. EuFe<sub>2</sub>As<sub>2</sub>-based iron pnictides could offer an interesting plateau to study their relationship that has attracted considerable attention. So far, two magnetic phase transitions were observed in EuFe<sub>2</sub>As<sub>2</sub>-based crystal, which were deemed to originate from the itinerant Fe moments (~190 K) and the localized Eu<sup>2+</sup> moments (~19 K), respectively. Here, we systematically studied the heat capacity for the EuFe<sub>2</sub>(As<inline-formula>\u0000<tex-math><?CDATA $ _{1-x}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mrow></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math><inline-graphic xlink:href=\"njpad7494ieqn3.gif\"></inline-graphic></inline-formula>P<sub><italic toggle=\"yes\">x</italic></sub>)<sub>2</sub> crystals with <italic toggle=\"yes\">x</italic> = 0.21 (optimally doped) and <italic toggle=\"yes\">x</italic> = 0.29 (overdoped). We have found two new magnetic orders in the superconducting state (ranging from 0.4 to 1.2 K) in the optimally doped crystal. As more P was introduced into the As site, one of the magnetic orders becomes absent in the overdoped crystal. Additionally, we observed strong field and orientation dependence in heat capacity. The present findings in EuFe<sub>2</sub>(As<inline-formula>\u0000<tex-math><?CDATA $ _{1-x}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mrow></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math><inline-graphic xlink:href=\"njpad7494ieqn4.gif\"></inline-graphic></inline-formula>P<sub><italic toggle=\"yes\">x</italic></sub>)<sub>2</sub> have detected the new low-temperature magnetic orders, which may originate from the localized Eu<sup>2+</sup> spins order or the spin reorientation.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"33 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142214701","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
In theoretical research framework of acoustics or optics, how to provide stable and efficient experimental vortex sources with arbitrary orbital angular momentum (OAM) (especially with larger OAM) is a highly challenging research topic. Here, we propose and demonstrate the general principle of two different methods to generate vortex sources with arbitrary OAM, based on the point-sources array and acoustic metamaterials, respectively. Specifically, the general synthetic law is summarized from the analytical perspective behind generating two-dimensional vortex waves using different point sources with different phases, and the design flexibility of acoustic metamaterials is also utilized to provide an ideal solution for generating vortex sources with larger OAM. Besides, we qualitatively and quantitatively determine the OAM of generated vortex waves through simple formulas, and briefly discuss the applicability and stability of two different methods with complementary advantages. The principles of vortex sources generation revealed in this work provide direct theoretical support for the experimental exploration of interactions between multiphysics fields and complex media, with potential applications in vortex fields manipulation and OAM detection.
{"title":"Efficient approach for generating vortex sources with arbitrary orbital angular momentum in acoustic experiments","authors":"Zhanlei Hao, Songsong Li, Yadong Xu, Shan Zhu, Huanyang Chen","doi":"10.1088/1367-2630/ad73fc","DOIUrl":"https://doi.org/10.1088/1367-2630/ad73fc","url":null,"abstract":"In theoretical research framework of acoustics or optics, how to provide stable and efficient experimental vortex sources with arbitrary orbital angular momentum (OAM) (especially with larger OAM) is a highly challenging research topic. Here, we propose and demonstrate the general principle of two different methods to generate vortex sources with arbitrary OAM, based on the point-sources array and acoustic metamaterials, respectively. Specifically, the general synthetic law is summarized from the analytical perspective behind generating two-dimensional vortex waves using different point sources with different phases, and the design flexibility of acoustic metamaterials is also utilized to provide an ideal solution for generating vortex sources with larger OAM. Besides, we qualitatively and quantitatively determine the OAM of generated vortex waves through simple formulas, and briefly discuss the applicability and stability of two different methods with complementary advantages. The principles of vortex sources generation revealed in this work provide direct theoretical support for the experimental exploration of interactions between multiphysics fields and complex media, with potential applications in vortex fields manipulation and OAM detection.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"59 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142214501","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-05DOI: 10.1088/1367-2630/ad7491
Junchi Li
Since the ingenious discovery of zero-determinant (ZD) strategies by Press and Dyson, many efforts have been devoted to the evolutionary performance of ZD strategies. Recently, the effects of higher-order interactions on evolutionary games have attracted widespread interests, whereas it remains unknown how higher-order interactions affect the evolutionary performance of ZD strategies. This paper focuses on the role of higher-order interactions on evolutionary ZD strategies in iterated public goods game, where the baseline payoff is a key parameter to describe nodes’ extent of reciprocity in both first-order and second-order interactions. Through the adaptive-like dynamics, we found that there is a critical value of each network, above which the networked game will converge to a consensus state where all the nodes obtain the same payoff. This critical value is significantly affected by the relative strength of higher-order interactions with a U-shaped trend. Numerical simulations are carried out to explore how the network structures affect the dynamics. The results in networks with different sizes indicate that networks with higher average degree are more easily to converge to the consensus state. The simulations on a real-world network further support the theoretical conclusions.
自从普雷斯和戴森巧妙地发现了零判定（ZD）策略以来，人们一直致力于研究ZD策略的演化性能。最近，高阶交互作用对演化博弈的影响引起了广泛的兴趣，而高阶交互作用如何影响 ZD 策略的演化表现却仍是未知数。本文重点研究了迭代公共物品博弈中高阶互动对ZD策略演化的作用，其中基线报酬是描述节点在一阶和二阶互动中互惠程度的关键参数。通过类似自适应的动力学，我们发现每个网络都有一个临界值，超过这个临界值，网络博弈就会收敛到所有节点都获得相同报酬的共识状态。这个临界值受高阶交互作用相对强度的影响很大，呈 U 型趋势。我们进行了数值模拟，以探索网络结构如何影响动态变化。不同规模网络的结果表明，平均度越高的网络越容易趋同于共识状态。对现实世界网络的模拟进一步支持了理论结论。
{"title":"Higher-order interactions and zero-determinant strategies in the public goods game","authors":"Junchi Li","doi":"10.1088/1367-2630/ad7491","DOIUrl":"https://doi.org/10.1088/1367-2630/ad7491","url":null,"abstract":"Since the ingenious discovery of zero-determinant (ZD) strategies by Press and Dyson, many efforts have been devoted to the evolutionary performance of ZD strategies. Recently, the effects of higher-order interactions on evolutionary games have attracted widespread interests, whereas it remains unknown how higher-order interactions affect the evolutionary performance of ZD strategies. This paper focuses on the role of higher-order interactions on evolutionary ZD strategies in iterated public goods game, where the baseline payoff is a key parameter to describe nodes’ extent of reciprocity in both first-order and second-order interactions. Through the adaptive-like dynamics, we found that there is a critical value of each network, above which the networked game will converge to a consensus state where all the nodes obtain the same payoff. This critical value is significantly affected by the relative strength of higher-order interactions with a U-shaped trend. Numerical simulations are carried out to explore how the network structures affect the dynamics. The results in networks with different sizes indicate that networks with higher average degree are more easily to converge to the consensus state. The simulations on a real-world network further support the theoretical conclusions.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"20 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142214702","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-03DOI: 10.1088/1367-2630/ad6ead
Yu Zhang, Haowei Chen, Qiyu Chen, Jie Ding, Xiang Li
The resilience and adaptability of complex networks is crucial in ensuring their functionality against disruptions. Particularly, maintaining network connectivity under various attack scenarios is a key aspect of such resilience. Network connectivity refers to the degree to which nodes within a network are interconnected and able to exchange information or resources. Its robustness reflects the ability of a network to maintain connectivity under various attacks. Such ability has profound physical significance, ensuring the stability and reliability of real-world systems. Currently, connectivity robustness assessments rely heavily on very time-consuming attack simulations. This paper introduces a graph neural network framework for network connectivity robustness learning (GCRL) to advance the study of network connectivity robustness. GCRL transforms initial degree distributions and network topology into informative embedding vectors, which are then processed by a robustness learning module mainly composed of multi-layer perceptron, achieving both high speed and precision. Our extensive experiments demonstrate the superior performance of GCRL obtained in less time compared to existing methods, especially in tough scenarios where test data distributions significantly differ from the training set. The framework also shows adaptability to networks of different sizes, making it a more generalized solution for complex network robustness learning.
{"title":"GCRL: a graph neural network framework for network connectivity robustness learning","authors":"Yu Zhang, Haowei Chen, Qiyu Chen, Jie Ding, Xiang Li","doi":"10.1088/1367-2630/ad6ead","DOIUrl":"https://doi.org/10.1088/1367-2630/ad6ead","url":null,"abstract":"The resilience and adaptability of complex networks is crucial in ensuring their functionality against disruptions. Particularly, maintaining network connectivity under various attack scenarios is a key aspect of such resilience. Network connectivity refers to the degree to which nodes within a network are interconnected and able to exchange information or resources. Its robustness reflects the ability of a network to maintain connectivity under various attacks. Such ability has profound physical significance, ensuring the stability and reliability of real-world systems. Currently, connectivity robustness assessments rely heavily on very time-consuming attack simulations. This paper introduces a graph neural network framework for network connectivity robustness learning (GCRL) to advance the study of network connectivity robustness. GCRL transforms initial degree distributions and network topology into informative embedding vectors, which are then processed by a robustness learning module mainly composed of multi-layer perceptron, achieving both high speed and precision. Our extensive experiments demonstrate the superior performance of GCRL obtained in less time compared to existing methods, especially in tough scenarios where test data distributions significantly differ from the training set. The framework also shows adaptability to networks of different sizes, making it a more generalized solution for complex network robustness learning.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"2 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142214493","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-02DOI: 10.1088/1367-2630/ad50fe
Hua-Jie Hu, He-He Li, Xin-Zhong Li
In this study, the spatial mode evolution of a chiral polarized beam during reflection on an isotropic medium surface at Brewster angle is both theoretically and experimentally investigated. In this process, the topological charge of the reflection field’s horizontal component increases (decreases) by one, relative to the specific left (right) elliptical polarization incident beam. While incident li-order vortex beam is in a certain polarization state, the intensity distribution of the reflection field’s horizontal component appears as the interference pattern of the li±1-order output vortex beams. The conversion occurs between the spin and orbital angular momentum and does not violate the conservation of the total angular momentum. We explain the physical mechanism of this phenomenon using phase shift theorem, and analyze the effect of ellipticity and polarization angle on this physical phenomenon.
{"title":"Spatial mode conversion of a reflected polarized beam from an isotropic medium at brewster angle","authors":"Hua-Jie Hu, He-He Li, Xin-Zhong Li","doi":"10.1088/1367-2630/ad50fe","DOIUrl":"https://doi.org/10.1088/1367-2630/ad50fe","url":null,"abstract":"In this study, the spatial mode evolution of a chiral polarized beam during reflection on an isotropic medium surface at Brewster angle is both theoretically and experimentally investigated. In this process, the topological charge of the reflection field’s horizontal component increases (decreases) by one, relative to the specific left (right) elliptical polarization incident beam. While incident <italic toggle=\"yes\">l</italic><sub><italic toggle=\"yes\">i</italic></sub>-order vortex beam is in a certain polarization state, the intensity distribution of the reflection field’s horizontal component appears as the interference pattern of the <inline-formula>\u0000<tex-math><?CDATA $l_{i}pm 1$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>l</mml:mi><mml:mrow><mml:mi>i</mml:mi></mml:mrow></mml:msub><mml:mo>±</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:math><inline-graphic xlink:href=\"njpad50feieqn1.gif\"></inline-graphic></inline-formula>-order output vortex beams. The conversion occurs between the spin and orbital angular momentum and does not violate the conservation of the total angular momentum. We explain the physical mechanism of this phenomenon using phase shift theorem, and analyze the effect of ellipticity and polarization angle on this physical phenomenon.","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"6 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142214496","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-02DOI: 10.1088/1367-2630/ad7281
Tingting Shi, Wei Zhang, C A R Sá de Melo
We discuss standard and tighter upper bounds on the critical temperature <inline-formula> <tex-math><?CDATA $T_textrm{c}$?></tex-math><mml:math overflow="scroll"><mml:mrow><mml:msub><mml:mi>T</mml:mi><mml:mtext>c</mml:mtext></mml:msub></mml:mrow></mml:math><inline-graphic xlink:href="njpad7281ieqn1.gif"></inline-graphic></inline-formula> of two-dimensional superfluids and superconductors versus particle density <italic toggle="yes">n</italic> or filling factor <italic toggle="yes">ν</italic> for continuum and lattice systems from the Bardeen–Cooper–Schrieffer (BCS) to the Bose regime. We consider only one-band Hamiltonians, where the transition from the normal to the superfluid (superconducting) phase is governed by the Berezinskii–Kosterlitz–Thouless (BKT) mechanism of vortex-antivortex binding, such that a direct relation between the superfluid density tensor and <inline-formula> <tex-math><?CDATA $T_textrm{c}$?></tex-math><mml:math overflow="scroll"><mml:mrow><mml:msub><mml:mi>T</mml:mi><mml:mtext>c</mml:mtext></mml:msub></mml:mrow></mml:math><inline-graphic xlink:href="njpad7281ieqn2.gif"></inline-graphic></inline-formula> exists. The standard critical temperature upper bound <inline-formula> <tex-math><?CDATA $T_textrm{c}^{mathrm{up1}}$?></tex-math><mml:math overflow="scroll"><mml:mrow><mml:msubsup><mml:mi>T</mml:mi><mml:mtext>c</mml:mtext><mml:mrow><mml:mrow><mml:mi>up</mml:mi><mml:mn>1</mml:mn></mml:mrow></mml:mrow></mml:msubsup></mml:mrow></mml:math><inline-graphic xlink:href="njpad7281ieqn3.gif"></inline-graphic></inline-formula> is obtained from the Ferrell-Glover-Tinkham sum rule for the optical conductivity, which constrains the superfluid density tensor components. We demonstrate that it is imperative to consider at least the full effect of phase fluctuations of the order parameter for superfluidity (superconductivity) and use the renormalization group to obtain the phase-fluctuation critical temperature <inline-formula> <tex-math><?CDATA $T_textrm{c}^{,theta}$?></tex-math><mml:math overflow="scroll"><mml:mrow><mml:msubsup><mml:mi>T</mml:mi><mml:mtext>c</mml:mtext><mml:mrow><mml:mstyle scriptlevel="0"></mml:mstyle><mml:mi>θ</mml:mi></mml:mrow></mml:msubsup></mml:mrow></mml:math><inline-graphic xlink:href="njpad7281ieqn4.gif"></inline-graphic></inline-formula>, a much tighter bound to the critical temperature supremum than <inline-formula> <tex-math><?CDATA $T_textrm{c}^{mathrm{up1}}$?></tex-math><mml:math overflow="scroll"><mml:mrow><mml:msubsup><mml:mi>T</mml:mi><mml:mtext>c</mml:mtext><mml:mrow><mml:mrow><mml:mi>up</mml:mi><mml:mn>1</mml:mn></mml:mrow></mml:mrow></mml:msubsup></mml:mrow></mml:math><inline-graphic xlink:href="njpad7281ieqn5.gif"></inline-graphic></inline-formula> over a wide range of densities or filling factors. We also discuss a fundamental difference between superfluids and superconductors in regards to the vortex core energy dependence on density. Going beyond phase fluctuations, we note that theories including
{"title":"Tighter upper bounds on the critical temperature of two-dimensional superfluids and superconductors from the BCS to the Bose regime","authors":"Tingting Shi, Wei Zhang, C A R Sá de Melo","doi":"10.1088/1367-2630/ad7281","DOIUrl":"https://doi.org/10.1088/1367-2630/ad7281","url":null,"abstract":"We discuss standard and tighter upper bounds on the critical temperature <inline-formula>\u0000<tex-math><?CDATA $T_textrm{c}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>T</mml:mi><mml:mtext>c</mml:mtext></mml:msub></mml:mrow></mml:math><inline-graphic xlink:href=\"njpad7281ieqn1.gif\"></inline-graphic></inline-formula> of two-dimensional superfluids and superconductors versus particle density <italic toggle=\"yes\">n</italic> or filling factor <italic toggle=\"yes\">ν</italic> for continuum and lattice systems from the Bardeen–Cooper–Schrieffer (BCS) to the Bose regime. We consider only one-band Hamiltonians, where the transition from the normal to the superfluid (superconducting) phase is governed by the Berezinskii–Kosterlitz–Thouless (BKT) mechanism of vortex-antivortex binding, such that a direct relation between the superfluid density tensor and <inline-formula>\u0000<tex-math><?CDATA $T_textrm{c}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>T</mml:mi><mml:mtext>c</mml:mtext></mml:msub></mml:mrow></mml:math><inline-graphic xlink:href=\"njpad7281ieqn2.gif\"></inline-graphic></inline-formula> exists. The standard critical temperature upper bound <inline-formula>\u0000<tex-math><?CDATA $T_textrm{c}^{mathrm{up1}}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msubsup><mml:mi>T</mml:mi><mml:mtext>c</mml:mtext><mml:mrow><mml:mrow><mml:mi>up</mml:mi><mml:mn>1</mml:mn></mml:mrow></mml:mrow></mml:msubsup></mml:mrow></mml:math><inline-graphic xlink:href=\"njpad7281ieqn3.gif\"></inline-graphic></inline-formula> is obtained from the Ferrell-Glover-Tinkham sum rule for the optical conductivity, which constrains the superfluid density tensor components. We demonstrate that it is imperative to consider at least the full effect of phase fluctuations of the order parameter for superfluidity (superconductivity) and use the renormalization group to obtain the phase-fluctuation critical temperature <inline-formula>\u0000<tex-math><?CDATA $T_textrm{c}^{,theta}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msubsup><mml:mi>T</mml:mi><mml:mtext>c</mml:mtext><mml:mrow><mml:mstyle scriptlevel=\"0\"></mml:mstyle><mml:mi>θ</mml:mi></mml:mrow></mml:msubsup></mml:mrow></mml:math><inline-graphic xlink:href=\"njpad7281ieqn4.gif\"></inline-graphic></inline-formula>, a much tighter bound to the critical temperature supremum than <inline-formula>\u0000<tex-math><?CDATA $T_textrm{c}^{mathrm{up1}}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msubsup><mml:mi>T</mml:mi><mml:mtext>c</mml:mtext><mml:mrow><mml:mrow><mml:mi>up</mml:mi><mml:mn>1</mml:mn></mml:mrow></mml:mrow></mml:msubsup></mml:mrow></mml:math><inline-graphic xlink:href=\"njpad7281ieqn5.gif\"></inline-graphic></inline-formula> over a wide range of densities or filling factors. We also discuss a fundamental difference between superfluids and superconductors in regards to the vortex core energy dependence on density. Going beyond phase fluctuations, we note that theories including ","PeriodicalId":19181,"journal":{"name":"New Journal of Physics","volume":"41 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142214498","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2024-09-02DOI: 10.1088/1367-2630/ad69b7
Sven Erik Ilse, René Nacke, Gisela Schütz, Eberhard Goering
Thin buried magnetic layers ranging from thicknesses of a few atomic monolayers to several nanometers are omnipresent in the fields of magnetism and spintronics. For the functionality and fine tuning of devices build with such layers, exact knowledge of the depth dependent magnetic properties is essential. Especially the interfacial magnetic properties are important. Hence, understanding how magnetism is affected by structural variations, such as thickness or interface roughness, is mandatory. In this study, we use x-ray resonant magnetic reflectometry and magnetometry to study the high-resolution depth dependent magnetization profiles of thin magnetic transition metal layers sandwiched between an oxide and chromium layer. Compared to bulk materials, the room temperature saturation magnetization of these layers is reduced by up to 67%. These reductions are extremely sensitive to small structural variations. From the magnetic depth profiles, we disentangle different effects contributing to the magnetization reduction and the exact magnetic properties of the interface.
在磁学和自旋电子学领域，厚度从几个原子单层到几个纳米不等的薄埋磁层无处不在。要实现使用此类磁层构建的设备的功能和微调，就必须准确了解与深度相关的磁性能。界面磁特性尤其重要。因此，了解磁性如何受到厚度或界面粗糙度等结构变化的影响至关重要。在这项研究中，我们使用 X 射线共振磁反射仪和磁力仪研究了夹在氧化物和铬层之间的磁性过渡金属薄层的高分辨率深度磁化曲线。与块状材料相比，这些层的室温饱和磁化率降低了高达 67%。这些降低对微小的结构变化极为敏感。从磁性深度剖面图中，我们可以分辨出导致磁化降低的不同效应以及界面的确切磁性。
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Pub Date : 2024-09-02DOI: 10.1088/1367-2630/ad7280
R Babjak, B Martinez, M Krus, M Vranic
Direct laser acceleration has proven to be an efficient source of high-charge electron bunches and high brilliance x-rays. However, an analytical description of the acceleration in the interaction with varying plasma density targets is still missing. Here, we provide an analytical estimate of the maximum energies that electrons can achieve in such a case. We demonstrate that the maximum energy depends on the local electron properties at the moment when the electron fulfills the resonant condition at the beginning of the acceleration. This knowledge enables density shaping for various purposes. One application is to decrease the required acceleration distance needed to achieve the maximum electron energy. Another use for density tailoring is to achieve acceleration beyond the radiation reaction limit. We derive the energy scaling law that is valid for arbitrary density profile that varies slowly compared with the betatron period. Our results can be applied to electron heating in exponential preplasma of thin foils, ablating plasma plumes, or gas jets with long-scale ramp-up.
事实证明，直接激光加速是产生高电荷电子束和高亮度 X 射线的有效来源。然而，对于与不同等离子体密度目标相互作用时的加速度，目前仍缺乏分析描述。在这里，我们对电子在这种情况下所能达到的最大能量进行了分析估算。我们证明，最大能量取决于电子在加速开始时满足共振条件时的局部电子特性。利用这一知识，可以为各种目的进行密度整形。其中一个应用是减少达到最大电子能量所需的加速距离。密度调整的另一个用途是实现超越辐射反应极限的加速。我们推导出了能量缩放定律，该定律适用于与贝塔特龙周期相比变化缓慢的任意密度曲线。我们的结果可以应用于薄金属箔的指数前等离子体、烧蚀等离子体羽流或具有长尺度斜升的气体射流中的电子加热。
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Pub Date : 2024-08-30DOI: 10.1088/1367-2630/ad7167
Lucas E A Porto, Gabriel Ruffolo, Rafael Rabelo, Marcelo Terra Cunha, Paweł Kurzyński
The relations between Bell nonlocality and Kochen–Specker contextuality have been subject of research from many different perspectives in the last decades. Recently, some interesting results on these relations have been explored in the so-called generalized Bell scenarios, that is, scenarios where Bell spatial separation (or agency independence) coexist with (at least one of the) parties’ ability to perform compatible measurements at each round of the experiment. When this party has an n-cycle compatiblity setup, it was first claimed that Bell nonlocality could not be concomitantly observed with contextuality at this party’s local experiment. However, by a more natural reading of the definition of locality, it turns out that both Bell nonlocality and local contextuality can, in fact, be jointly present. In spite of it, in this work we prove that in the simplest of those scenarios there cannot be arbitrary amounts of both of these two resources together. That is, in these cases we show that the violation of any Bell inequality limits the possible violations of any local noncontextuality inequality. We also explore this trade-off relation using quantifiers of nonlocality and contextuality, discussing how such a relation can be understood in terms of a ‘global’ notion of contextuality, and we study possible extensions of this result to other scenarios.
在过去的几十年里，贝尔非位置性和 Kochen-Specker 背景性之间的关系一直是许多不同视角的研究课题。最近，人们在所谓的广义贝尔情境（即贝尔空间分离（或机构独立）与（至少一方）在每轮实验中进行兼容测量的能力并存的情境）中探索了这些关系的一些有趣结果。当这一方拥有 n 周期兼容设置时，最初有人声称在这一方的本地实验中，贝尔非位置性与情境性无法同时被观测到。然而，通过对局部性定义进行更自然的解读，我们发现贝尔非局部性和局部上下文性实际上是可以同时存在的。尽管如此，我们还是在这项工作中证明，在最简单的情况下，这两种资源不可能任意同时存在。也就是说，在这些情况下，我们证明了对任何贝尔不等式的违反都会限制对任何本地非语境不等式的可能违反。我们还使用非局部性和上下文性的量词探讨了这种权衡关系，讨论了如何从上下文性的 "全局 "概念来理解这种关系，并研究了将这一结果扩展到其他情景的可能性。
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