Pub Date : 2026-01-28DOI: 10.1088/1361-6633/ae3eb2
Michał Horodecki,Michal Studzinski,Marek Mozrzymas
In this work, we present an algorithmic treatment of the representation theory of the algebra of partially transposed permutation operators, denoted by $mathcal{A}^d_{p,p}$, which is a matrix representation of the abstract walled Brauer algebra.
We provide an explicit and fully developed framework for constructing irreducible matrix units within the algebra. In contrast to the established earlier Gelfand-Tsetlin type constructions, the presented matrix units are adapted to the action of the subalgebra $mathbb{C}[mathfrak{S}_p] times mathbb{C}[mathfrak{S}_p]$, where $mathfrak{S}_p$ is the symmetric group. What is more, the basis is constructed in such a way that it produces the decomposition of the algebra into a direct sum of ideals, in contrast to its nested structure considered before. The decomposition of this kind has not been considered before in full generality. Our method reveals a recursive scheme for generating irreducible matrix units in all ideals of $mathcal{A}^d_{p,p}$, offering a systematic approach that applies to small system sizes and arbitrary local dimensions. We apply the developed formalism to the algebra $mathcal{A}^d_{2,2}$ and illustrate the algorithm in practice. In addition, using the constructed basis, we proved a novel contraction theorem for the elements from $mathcal{A}^d_{3,3}$, which is the starting point for further investigations.
{"title":"Iterative construction of 𝕾p× 𝕾pgroup-adapted irreducible matrix units for the walled Brauer algebra.","authors":"Michał Horodecki,Michal Studzinski,Marek Mozrzymas","doi":"10.1088/1361-6633/ae3eb2","DOIUrl":"https://doi.org/10.1088/1361-6633/ae3eb2","url":null,"abstract":"In this work, we present an algorithmic treatment of the representation theory of the algebra of partially transposed permutation operators, denoted by $mathcal{A}^d_{p,p}$, which is a matrix representation of the abstract walled Brauer algebra.

We provide an explicit and fully developed framework for constructing irreducible matrix units within the algebra. In contrast to the established earlier Gelfand-Tsetlin type constructions, the presented matrix units are adapted to the action of the subalgebra $mathbb{C}[mathfrak{S}_p] times mathbb{C}[mathfrak{S}_p]$, where $mathfrak{S}_p$ is the symmetric group. What is more, the basis is constructed in such a way that it produces the decomposition of the algebra into a direct sum of ideals, in contrast to its nested structure considered before. The decomposition of this kind has not been considered before in full generality. Our method reveals a recursive scheme for generating irreducible matrix units in all ideals of $mathcal{A}^d_{p,p}$, offering a systematic approach that applies to small system sizes and arbitrary local dimensions. We apply the developed formalism to the algebra $mathcal{A}^d_{2,2}$ and illustrate the algorithm in practice. In addition, using the constructed basis, we proved a novel contraction theorem for the elements from $mathcal{A}^d_{3,3}$, which is the starting point for further investigations.","PeriodicalId":21110,"journal":{"name":"Reports on Progress in Physics","volume":"73 1","pages":""},"PeriodicalIF":18.1,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146069903","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 : 2026-01-27DOI: 10.1088/1361-6633/ae3e3d
Su Jae Kim,Seon Je Kim,Young-Hoon Kim,Tae-In Jeong,Min-Hyoung Jung,Hee-Beom Lee,Jongkyoon Park,Sehyeon Kim,Ganbat Duvjir,Yousil Lee,Jegon Lee,Woo Seok Choi,Jungdae Kim,Hu Young Jeong,Seungchul Kim,Se-Young Jeong,Young-Min Kim
Wafer-scale growth of metallic films into single crystals is challenging due to large lattice mismatch and uncontrollable atom stacking during deposition. Here, single-crystalline Ag(111) films are grown on atomically flat Cu(111) buffer layers using atomic sputtering epitaxy, despite the significant Ag/Cu lattice mismatch (about 13%). The mismatch strain is confined to the first Ag monoatomic interface layer and does not spread into the adjacent Ag layers. This effective strain relaxation occurs through regulated in-plane displacements of Ag atoms where Ag and Cu atoms meet periodically. Although the grain boundary-free Ag thin films initially exhibited twin boundaries, we successfully demonstrated conditions that significantly reduced them -a feat considered challenging in thin film growth technology.
{"title":"Homoepitaxy-like heteroepitaxy via monolayer interface achieves grain-boundary-free ultraflat silver thin films.","authors":"Su Jae Kim,Seon Je Kim,Young-Hoon Kim,Tae-In Jeong,Min-Hyoung Jung,Hee-Beom Lee,Jongkyoon Park,Sehyeon Kim,Ganbat Duvjir,Yousil Lee,Jegon Lee,Woo Seok Choi,Jungdae Kim,Hu Young Jeong,Seungchul Kim,Se-Young Jeong,Young-Min Kim","doi":"10.1088/1361-6633/ae3e3d","DOIUrl":"https://doi.org/10.1088/1361-6633/ae3e3d","url":null,"abstract":"Wafer-scale growth of metallic films into single crystals is challenging due to large lattice mismatch and uncontrollable atom stacking during deposition. Here, single-crystalline Ag(111) films are grown on atomically flat Cu(111) buffer layers using atomic sputtering epitaxy, despite the significant Ag/Cu lattice mismatch (about 13%). The mismatch strain is confined to the first Ag monoatomic interface layer and does not spread into the adjacent Ag layers. This effective strain relaxation occurs through regulated in-plane displacements of Ag atoms where Ag and Cu atoms meet periodically. Although the grain boundary-free Ag thin films initially exhibited twin boundaries, we successfully demonstrated conditions that significantly reduced them -a feat considered challenging in thin film growth technology.","PeriodicalId":21110,"journal":{"name":"Reports on Progress in Physics","volume":"105 1","pages":""},"PeriodicalIF":18.1,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146056568","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 : 2026-01-27DOI: 10.1088/1361-6633/ae3df8
K Halid Dinar,Romain Parret,Olivier Chuzel,Andrea Campos,Cedric Pardanaud
Raman spectroscopy is a widely utilized technique for the analysis of graphene materials within academic and industry contexts. This technique is characterized by its ease of implementation, rapidity, and non-destructive nature. Spectra resulting from this technique typically consist of two bands (G and 2D), which gives the spectra a seemingly simple appearance. Indeed, as early as 2007, Raman criteria were proposed to determine the number of layers in a stack based solely on the Raman spectrum. However, a multitude of studies published since 2007 have demonstrated that behind this apparent simplicity lie multiple effects that affect the G and 2D bands, thereby rendering interpretation complex and the determination of the number of layers in a stack uncertain. Furthermore, Raman spectroscopy has emerged as a pivotal technique for the analysis of twisted structures and diverse stacking sequences, such as ABA and ABC, which have culminated in significant discoveries, including strongly correlated states such as superconductivity and Mott insulating behavior. In addition to the resonance effects associated with superlattice formation, the shape of the 2D band provides valuable insight into stacking types, although its interpretation remains complex. In this article, we propose a methodology for interpreting the 2D Raman band that is informed by a comprehensive review of the extant literature as well as original data. A compendium of recommendations and a series of diagrams are also provided to address other physical effects that can complicate spectral interpretation.
{"title":"Focus on the Raman 2D band of the graphene materials: bibliographic review and guiding tools for determining number of layers and stacking configurations.","authors":"K Halid Dinar,Romain Parret,Olivier Chuzel,Andrea Campos,Cedric Pardanaud","doi":"10.1088/1361-6633/ae3df8","DOIUrl":"https://doi.org/10.1088/1361-6633/ae3df8","url":null,"abstract":"Raman spectroscopy is a widely utilized technique for the analysis of graphene materials within academic and industry contexts. This technique is characterized by its ease of implementation, rapidity, and non-destructive nature. Spectra resulting from this technique typically consist of two bands (G and 2D), which gives the spectra a seemingly simple appearance. Indeed, as early as 2007, Raman criteria were proposed to determine the number of layers in a stack based solely on the Raman spectrum. However, a multitude of studies published since 2007 have demonstrated that behind this apparent simplicity lie multiple effects that affect the G and 2D bands, thereby rendering interpretation complex and the determination of the number of layers in a stack uncertain. Furthermore, Raman spectroscopy has emerged as a pivotal technique for the analysis of twisted structures and diverse stacking sequences, such as ABA and ABC, which have culminated in significant discoveries, including strongly correlated states such as superconductivity and Mott insulating behavior. In addition to the resonance effects associated with superlattice formation, the shape of the 2D band provides valuable insight into stacking types, although its interpretation remains complex. In this article, we propose a methodology for interpreting the 2D Raman band that is informed by a comprehensive review of the extant literature as well as original data. A compendium of recommendations and a series of diagrams are also provided to address other physical effects that can complicate spectral interpretation.","PeriodicalId":21110,"journal":{"name":"Reports on Progress in Physics","volume":"64 1","pages":""},"PeriodicalIF":18.1,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146056569","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}
In complex oxides, charge carriers often couple strongly with lattice vibrations to form polaronsentangled electron-phonon quasiparticles whose transport properties remain difficult to characterize. Experimental access to intrinsic polaronic transport requires ultraclean samples, while theoretical description demands methods beyond low-order perturbation theory. Here, we show a predictive theory-experiment workflow to study polaron transport in complex oxides.Focusing on a prototypical polaronic oxide, anatase TiO 2 , we combine growth of high-quality oxygen-vacancy-doped films using hybrid molecular beam epitaxy (MBE) with a first-principles electron-phonon diagrammatic Monte Carlo (FEP-DMC) framework recently developed for accurate polaron predictions. Our films exhibit record-high electron mobility for anatase TiO 2 , in excellent agreement with FEP-DMC calculations conducted prior to experiment, which predict a room-temperature mobility of 45 ± 15 cm 2 V -1 s -1 and a mobility-temperature scaling of μ ∝ T -1.9 ± 0.077 . Microscopic analysis using scanning transmission electron microscopy and X-ray photoelectron spectroscopy reveals the role of oxygen vacancies in modulating transport at lower temperatures. FEP-DMC further provides quantitative insight into polaron formation energy, phonon cloud distribution, lattice distortion around the polaron, and the polaronic contribution to mobility. Together, these results provide a deeper microscopic understanding of large-polaron transport in a complex oxide and provide the blueprint to characterize other polaronic materials.
在复杂的氧化物中，载流子经常与晶格振动强烈耦合，形成极极性非纠缠电子-声子准粒子，其输运性质仍然难以表征。本征极化输运的实验获取需要超净样品，而理论描述需要低阶微扰理论以外的方法。在这里，我们展示了一个预测理论-实验工作流程来研究复合氧化物中的极化子输运。以一种典型的极化子氧化物——钛矿二氧化钛为研究对象，我们利用混合分子束外延（MBE）和最近开发的用于精确极化子预测的第一性原理电子-声子图蒙特卡罗（FEP-DMC）框架，结合了高质量的氧空位掺杂薄膜的生长。我们的薄膜表现出了创纪录的高电子迁移率，与实验前进行的FEP-DMC计算非常吻合，预测其室温迁移率为45±15 cm 2 V -1 s -1，迁移温度标度为μ∝T -1.9±0.077。利用扫描透射电子显微镜和x射线光电子能谱的显微分析揭示了氧空位在低温下调制输运中的作用。FEP-DMC进一步提供了极化子形成能量、声子云分布、极化子周围的晶格畸变以及极化子对迁移率的贡献的定量见解。总之，这些结果为复杂氧化物中的大极化子输运提供了更深入的微观理解，并为表征其他极化子材料提供了蓝图。
{"title":"Understanding polaronic transport in complex oxides by combining precise synthesis and first-principles many-body theory.","authors":"Fengdeng Liu,Zhifei Yang,Yao Luo,Silu Guo,Chi Zhang,Sooho Choo,Xiaotian Xu,Seung Gyo Jeong,Jitin Sathish Kumar,Xiaojia Wang,Andre Mkhoyan,Marco Bernardi,Bharat Jalan","doi":"10.1088/1361-6633/ae3c3e","DOIUrl":"https://doi.org/10.1088/1361-6633/ae3c3e","url":null,"abstract":"In complex oxides, charge carriers often couple strongly with lattice vibrations to form polaronsentangled electron-phonon quasiparticles whose transport properties remain difficult to characterize. Experimental access to intrinsic polaronic transport requires ultraclean samples, while theoretical description demands methods beyond low-order perturbation theory. Here, we show a predictive theory-experiment workflow to study polaron transport in complex oxides.Focusing on a prototypical polaronic oxide, anatase TiO 2 , we combine growth of high-quality oxygen-vacancy-doped films using hybrid molecular beam epitaxy (MBE) with a first-principles electron-phonon diagrammatic Monte Carlo (FEP-DMC) framework recently developed for accurate polaron predictions. Our films exhibit record-high electron mobility for anatase TiO 2 , in excellent agreement with FEP-DMC calculations conducted prior to experiment, which predict a room-temperature mobility of 45 ± 15 cm 2 V -1 s -1 and a mobility-temperature scaling of μ ∝ T -1.9 ± 0.077 . Microscopic analysis using scanning transmission electron microscopy and X-ray photoelectron spectroscopy reveals the role of oxygen vacancies in modulating transport at lower temperatures. FEP-DMC further provides quantitative insight into polaron formation energy, phonon cloud distribution, lattice distortion around the polaron, and the polaronic contribution to mobility. Together, these results provide a deeper microscopic understanding of large-polaron transport in a complex oxide and provide the blueprint to characterize other polaronic materials.","PeriodicalId":21110,"journal":{"name":"Reports on Progress in Physics","volume":"47 1","pages":""},"PeriodicalIF":18.1,"publicationDate":"2026-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146021452","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 : 2026-01-16DOI: 10.1088/1361-6633/ae3982
Murod Mirzhalilov,Nandini Trivedi,Mohit Randeria
We theoretically analyze the topological insulator (TI) surface state mediated interactions between local moments in a proximate 2D ferromagnetic insulator (FMI) motivated by recent experiments that show a significant increase in the Curie temperature Tc of FMI-TI heterostructures. Such interactions have been investigated earlier with a focus on dilute magnetic dopants in TIs. Our problem involves a dense set of moments for which we find that the short range Bloembergen-Rowland interaction, arising from virtual particle-hole transitions between the valence and conduction bands, dominates over the oscillatory Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. We show that the Tc enhancement is proportional to the Van Vleck susceptibility and that the spin-momentum locking of surface states leads to out-of-plane ferromagnetic order in the FMI. We investigate how the hybridization between top and bottom surfaces in a thin TI film impacts Tc enhancement, and show how our results can help understand recent experiments on atomically thin Cr2Te3-(Bi,Sb)2Te3. Our results advance the understanding of magnetic interactions relevant for TI-based spintronic and magnonic devices.
{"title":"Enhancement of Curie Temperature in Ferromagnetic Insulator-Topological Insulator Heterostructures.","authors":"Murod Mirzhalilov,Nandini Trivedi,Mohit Randeria","doi":"10.1088/1361-6633/ae3982","DOIUrl":"https://doi.org/10.1088/1361-6633/ae3982","url":null,"abstract":"We theoretically analyze the topological insulator (TI) surface state mediated interactions between local moments in a proximate 2D ferromagnetic insulator (FMI) motivated by recent experiments that show a significant increase in the Curie temperature Tc of FMI-TI heterostructures. Such interactions have been investigated earlier with a focus on dilute magnetic dopants in TIs. Our problem involves a dense set of moments for which we find that the short range Bloembergen-Rowland interaction, arising from virtual particle-hole transitions between the valence and conduction bands, dominates over the oscillatory Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. We show that the Tc enhancement is proportional to the Van Vleck susceptibility and that the spin-momentum locking of surface states leads to out-of-plane ferromagnetic order in the FMI. We investigate how the hybridization between top and bottom surfaces in a thin TI film impacts Tc enhancement, and show how our results can help understand recent experiments on atomically thin Cr2Te3-(Bi,Sb)2Te3. Our results advance the understanding of magnetic interactions relevant for TI-based spintronic and magnonic devices.","PeriodicalId":21110,"journal":{"name":"Reports on Progress in Physics","volume":"24 1","pages":""},"PeriodicalIF":18.1,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145986350","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 : 2026-01-16DOI: 10.1088/1361-6633/ae3983
Xiaoliang Xiao,Xingyu Yue,Jinyang Ni,Jin-Zhu Zhao,Ruiqiang Wang,Xin Wang,Guoqing Chang,Yuanjun Jin
Manipulating the nonlinear Hall effect (NLHE) through non-volatile approach is of great significance for device applications, yet effective gating control remains elusive. In this Letter, using first-principles calculations and symmetry analysis, we propose a universal design principle for gate-field control of the NLHE in bilayer systems. Using bilayer SnSe and SnTe, the well-known ferroelectric and thermoelectric materials, as examples, it reveals that the inherent hidden polarization can activate a layer-locked hidden Berry curvature dipole (BCD) under an applied gate field, thereby inducing a giant nonlinear Hall current. The hidden polarization locked to BCD in a gate field, experiences a pseudospin Zeeman field as a spin in magnetic field. Therefore, reversing the direction of the gate-field can switch the preferred pseudospin orientation, enabling the switchable second-order NLHE. This mechanism does not require intrinsic magnetism and provides a binary ON/OFF switching control method, greatly expanding the application potential of layered systems in nonlinear Hall transport. Our findings not only demonstrate the universal design principle of the switchable second-order NLHE but also can be extended to other gate-field-controllable nonlinear transport and nonlinear optics.
{"title":"A universal design principle for switchable control of the second-order nonlinear Hall effect.","authors":"Xiaoliang Xiao,Xingyu Yue,Jinyang Ni,Jin-Zhu Zhao,Ruiqiang Wang,Xin Wang,Guoqing Chang,Yuanjun Jin","doi":"10.1088/1361-6633/ae3983","DOIUrl":"https://doi.org/10.1088/1361-6633/ae3983","url":null,"abstract":"Manipulating the nonlinear Hall effect (NLHE) through non-volatile approach is of great significance for device applications, yet effective gating control remains elusive. In this Letter, using first-principles calculations and symmetry analysis, we propose a universal design principle for gate-field control of the NLHE in bilayer systems. Using bilayer SnSe and SnTe, the well-known ferroelectric and thermoelectric materials, as examples, it reveals that the inherent hidden polarization can activate a layer-locked hidden Berry curvature dipole (BCD) under an applied gate field, thereby inducing a giant nonlinear Hall current. The hidden polarization locked to BCD in a gate field, experiences a pseudospin Zeeman field as a spin in magnetic field. Therefore, reversing the direction of the gate-field can switch the preferred pseudospin orientation, enabling the switchable second-order NLHE. This mechanism does not require intrinsic magnetism and provides a binary ON/OFF switching control method, greatly expanding the application potential of layered systems in nonlinear Hall transport. Our findings not only demonstrate the universal design principle of the switchable second-order NLHE but also can be extended to other gate-field-controllable nonlinear transport and nonlinear optics.","PeriodicalId":21110,"journal":{"name":"Reports on Progress in Physics","volume":"83 1","pages":""},"PeriodicalIF":18.1,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145986351","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}
Physical reservoir computing (RC) systems have emerged as a prominent research frontier due to their exceptional efficiency in temporal information processing. However, existing implementations, predominantly utilizing resistive devices, face challenges pertaining to power efficiency and dynamic richness. Here, we propose a ferroelectric capacitor-linear capacitor (FC-LC) series device for RC implementation. By leveraging nonlinear polarization switching and back-switching, the FC-LC series device realizes two essential reservoir properties: nonlinearity and fading memory. In addition, the device exhibits an ultralow power consumption, which, along with its direct voltage readout capability, marks a significant advance over resistive reservoir devices. Moreover, the device features bidirectional operation and widely tunable time constants, thereby enhancing reservoir space dimensionality and state richness. Building upon these FC-LC series devices, a ferroelectric capacitive RC system is developed, which demonstrates superior performance in various benchmark tasks. By exploiting the bidirectional operation of the device, the RC system not only delivers enhanced performance in waveform classification but also enables highaccuracy multimodal digit recognition. Through strategically hybridizing the FC-LC series devices with varying time constants, the RC system achieves remarkable performance in Mackey-Glass time-series prediction. Our study paves the way for power-efficient, dynamicrich RC systems capable of handling diverse temporal tasks.
{"title":"Ultralow-power reservoir computing based on bidirectionally operable ferroelectric capacitors with tunable time constants.","authors":"Linyuan Mo,Zhen Fan,Jiali Ou,Zhiwei Chen,Haipeng Lin,Wenjie Hu,Wenjie Li,Meixia Li,Boyuan Cui,Hua Fan,Ruiqiang Tao,Guo Tian,Minghui Qin,Xubing Lu,Guofu Zhou,Xingsen Gao,Junming Liu","doi":"10.1088/1361-6633/ae3984","DOIUrl":"https://doi.org/10.1088/1361-6633/ae3984","url":null,"abstract":"Physical reservoir computing (RC) systems have emerged as a prominent research frontier due to their exceptional efficiency in temporal information processing. However, existing implementations, predominantly utilizing resistive devices, face challenges pertaining to power efficiency and dynamic richness. Here, we propose a ferroelectric capacitor-linear capacitor (FC-LC) series device for RC implementation. By leveraging nonlinear polarization switching and back-switching, the FC-LC series device realizes two essential reservoir properties: nonlinearity and fading memory. In addition, the device exhibits an ultralow power consumption, which, along with its direct voltage readout capability, marks a significant advance over resistive reservoir devices. Moreover, the device features bidirectional operation and widely tunable time constants, thereby enhancing reservoir space dimensionality and state richness. Building upon these FC-LC series devices, a ferroelectric capacitive RC system is developed, which demonstrates superior performance in various benchmark tasks. By exploiting the bidirectional operation of the device, the RC system not only delivers enhanced performance in waveform classification but also enables highaccuracy multimodal digit recognition. Through strategically hybridizing the FC-LC series devices with varying time constants, the RC system achieves remarkable performance in Mackey-Glass time-series prediction. Our study paves the way for power-efficient, dynamicrich RC systems capable of handling diverse temporal tasks.","PeriodicalId":21110,"journal":{"name":"Reports on Progress in Physics","volume":"268 1","pages":""},"PeriodicalIF":18.1,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145986347","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}
Negative thermal expansion (NTE) refers to volume contraction upon heating, but the intrinsic complexity of its physical mechanisms presents a fundamental challenge. α-Cu2V2O7 exhibits significant anisotropic NTE over a wider temperature range; however, its NTE mechanism has not been clearly elucidated. Herein, we systematically investigate the NTE mechanism of α-Cu2V2O7 using neutron powder diffraction, synchrotron radiation X-ray diffraction, and temperature- and pressure-dependent Raman spectra, and density functional theory calculations across 5 - 800 K. The structure exhibits a second-order Jahn-Teller (SOJT) effect, which is the primary cause of off-centering within the quasi-CuO6 octahedra. As temperature increases, the SOJT effect weakens, reducing the distortion of the driving force for off-centering; this causes the Cu atoms to shift in opposite directions, increasing symmetry. The anti-off-centering displacement of the Cu atoms toward the O4(long) atoms in the quasi-CuO6 octahedra compresses the Cu···Cu zigzag chains and reduces the spacing between orthogonal chains, resulting in the NTE behavior of α-Cu2V2O7. This study reveals a novel mechanism whereby the SOJT effect governs the displacement and symmetry of Cu atoms, providing crucial insight into the origin of NTE behavior in α-Cu2V2O7. These findings could help the community advance the understanding of NTE in anisotropic materials.
{"title":"Jahn-Teller distortions induced strong negative thermal expansion in α-Cu2V2O7.","authors":"Xiangkai Hao,Shibo Zhao,Qilong Gao,Yongqiang Qiao,Andrea Sanson,K Matan,G Gitgeatpong,Qiang Sun,Juan Guo,Feng Jin,Lunhua He,Shogo Kawaguchi,Erjun Liang,Jun Chen","doi":"10.1088/1361-6633/ae3853","DOIUrl":"https://doi.org/10.1088/1361-6633/ae3853","url":null,"abstract":"Negative thermal expansion (NTE) refers to volume contraction upon heating, but the intrinsic complexity of its physical mechanisms presents a fundamental challenge. α-Cu2V2O7 exhibits significant anisotropic NTE over a wider temperature range; however, its NTE mechanism has not been clearly elucidated. Herein, we systematically investigate the NTE mechanism of α-Cu2V2O7 using neutron powder diffraction, synchrotron radiation X-ray diffraction, and temperature- and pressure-dependent Raman spectra, and density functional theory calculations across 5 - 800 K. The structure exhibits a second-order Jahn-Teller (SOJT) effect, which is the primary cause of off-centering within the quasi-CuO6 octahedra. As temperature increases, the SOJT effect weakens, reducing the distortion of the driving force for off-centering; this causes the Cu atoms to shift in opposite directions, increasing symmetry. The anti-off-centering displacement of the Cu atoms toward the O4(long) atoms in the quasi-CuO6 octahedra compresses the Cu···Cu zigzag chains and reduces the spacing between orthogonal chains, resulting in the NTE behavior of α-Cu2V2O7. This study reveals a novel mechanism whereby the SOJT effect governs the displacement and symmetry of Cu atoms, providing crucial insight into the origin of NTE behavior in α-Cu2V2O7. These findings could help the community advance the understanding of NTE in anisotropic materials.","PeriodicalId":21110,"journal":{"name":"Reports on Progress in Physics","volume":"41 1","pages":""},"PeriodicalIF":18.1,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145971886","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 : 2025-12-15DOI: 10.1088/1361-6633/ae2ca2
Manlio De Domenico
The possibility that evolutionary forces -- together with a few fundamental factors such as thermodynamic constraints, specific computational features enabling information processing, and ecological processes -- might constrain the logic of living systems is tantalizing. However, it is often overlooked that any practical implementation of such a logic requires complementary circuitry that, in biological systems, happens through complex networks of genetic regulation, metabolic reactions, cellular signalling, communication, social and eusocial non-trivial organization. Here, we review and discuss how circuitries are not merely passive structures, but active agents of change that, by means of hierarchical and modular organization, are able to enhance and catalyze the evolution of evolvability. By analyzing the role of non-trivial topologies in major evolutionary transitions under the lens of statistical physics and nonlinear dynamics, we show that biological innovations are strictly related to circuitry and its deviation from trivial structures and (thermo)dynamic equilibria.
We argue that sparse heterogeneous networks such as hierarchical modular, which are ubiquitously observed in nature, are favored in terms of the trade-off between energetic costs for redundancy, error-correction and mantainance. We identify three main features -- namely, interconnectivity, plasticity and interdependency -- pointing towards a unifying framework for modeling the phenomenology, discussing them in terms of dynamical systems theory, non-equilibrium thermodynamics and evolutionary dynamics. Within this unified picture, we also show that "slow" evolutionary dynamics is an emergent phenomenon governed by the replicator-mutator equation as the direct consequence of a constrained variational nonequilibrium process. Overall, this work highlights how dynamical systems theory and nonequilibrium thermodynamics provide powerful analytical techniques to study biological complexity.
{"title":"Decoding the architecture of living systems.","authors":"Manlio De Domenico","doi":"10.1088/1361-6633/ae2ca2","DOIUrl":"https://doi.org/10.1088/1361-6633/ae2ca2","url":null,"abstract":"The possibility that evolutionary forces -- together with a few fundamental factors such as thermodynamic constraints, specific computational features enabling information processing, and ecological processes -- might constrain the logic of living systems is tantalizing. However, it is often overlooked that any practical implementation of such a logic requires complementary circuitry that, in biological systems, happens through complex networks of genetic regulation, metabolic reactions, cellular signalling, communication, social and eusocial non-trivial organization. Here, we review and discuss how circuitries are not merely passive structures, but active agents of change that, by means of hierarchical and modular organization, are able to enhance and catalyze the evolution of evolvability. By analyzing the role of non-trivial topologies in major evolutionary transitions under the lens of statistical physics and nonlinear dynamics, we show that biological innovations are strictly related to circuitry and its deviation from trivial structures and (thermo)dynamic equilibria. 

We argue that sparse heterogeneous networks such as hierarchical modular, which are ubiquitously observed in nature, are favored in terms of the trade-off between energetic costs for redundancy, error-correction and mantainance. We identify three main features -- namely, interconnectivity, plasticity and interdependency -- pointing towards a unifying framework for modeling the phenomenology, discussing them in terms of dynamical systems theory, non-equilibrium thermodynamics and evolutionary dynamics. Within this unified picture, we also show that \"slow\" evolutionary dynamics is an emergent phenomenon governed by the replicator-mutator equation as the direct consequence of a constrained variational nonequilibrium process. Overall, this work highlights how dynamical systems theory and nonequilibrium thermodynamics provide powerful analytical techniques to study biological complexity.","PeriodicalId":21110,"journal":{"name":"Reports on Progress in Physics","volume":"43 1","pages":""},"PeriodicalIF":18.1,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145760086","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}
Studies of ground-state topology in quantum materials have revealed the discovery of topological phases with novel Hall responses. Recently, the orbital Hall effect has drawn growing attention; however, the hidden origin behind large orbital Hall conductivity in insulators remains elusive. Here, we introduce the concept of orbital Chern insulators (OCIs), a previously unexplored topological phase in which orbital angular momentum drives nontrivial topology and hosts the orbital Hall effect in insulating systems. We establish a comprehensive orbital-topology-based framework for systematically characterizing OCIs, and identify monolayer blue phosphorene, a material previously regarded as a trivial insulator, hosting the first pure OCI with robust topological boundary states. We demonstrate that OCI is entirely orbital driven, fully disentangled from the spin and valley degrees of freedom, resulting in an orbital Hall effect that can be experimentally distinguished from the spin and valley Hall effects in insulating materials. Our work suggests a new avenue for exploring orbital topology in materials and advancing orbitronics-based technologies.
{"title":"Orbital topology induced orbital Hall effect in two-dimensional insulators.","authors":"Yueh-Ting Yao,Chia-Hung Chu,Arun Bansil,Hsin Lin,Tay-Rong Chang","doi":"10.1088/1361-6633/ae2a68","DOIUrl":"https://doi.org/10.1088/1361-6633/ae2a68","url":null,"abstract":"Studies of ground-state topology in quantum materials have revealed the discovery of topological phases with novel Hall responses. Recently, the orbital Hall effect has drawn growing attention; however, the hidden origin behind large orbital Hall conductivity in insulators remains elusive. Here, we introduce the concept of orbital Chern insulators (OCIs), a previously unexplored topological phase in which orbital angular momentum drives nontrivial topology and hosts the orbital Hall effect in insulating systems. We establish a comprehensive orbital-topology-based framework for systematically characterizing OCIs, and identify monolayer blue phosphorene, a material previously regarded as a trivial insulator, hosting the first pure OCI with robust topological boundary states. We demonstrate that OCI is entirely orbital driven, fully disentangled from the spin and valley degrees of freedom, resulting in an orbital Hall effect that can be experimentally distinguished from the spin and valley Hall effects in insulating materials. Our work suggests a new avenue for exploring orbital topology in materials and advancing orbitronics-based technologies.","PeriodicalId":21110,"journal":{"name":"Reports on Progress in Physics","volume":"35 1","pages":""},"PeriodicalIF":18.1,"publicationDate":"2025-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145710755","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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