The mobility of the Wigner solid on the superfluid $^3$He is determined by the momentum transfer from the scattered $^3$He quasiparticles at the free surface. The scattering process of the quasiparticles is classified into the normal reflection and the Andreev retroreflection. Since the quasiparticles nearly conserve the momentum in the process of the Andreev retroreflection at the free surface, the Andreev reflected quasiparticles do not produce a resistive force to the Wigner solid. In this report, we have analytically calculated the contribution of the Andreev retroreflection to the mobility of the Wigner solid on superfluid $^3$He-B by employing a realistic model order parameter with the free surface. The Andreev retroreflection is lacked for quasiparticles with energy above the bulk energy gap under the model order parameter. Then, the Andreev retroreflection does not contribute to a rise in the mobility of the Wigner solid on the superfluid $^3$He-B. The present model calculation is in good agreement with the previous experimental observation. We have also discussed the Andreev retroreflection under a self-consistently calculated order parameter.
{"title":"Contribution of Andreev reflection to the mobility of surface state electrons on superfluid $^3$He-B","authors":"Yasumasa Tsutsumi, Hiroki Ikegami, Kimitoshi Kono","doi":"arxiv-2406.14016","DOIUrl":"https://doi.org/arxiv-2406.14016","url":null,"abstract":"The mobility of the Wigner solid on the superfluid $^3$He is determined by\u0000the momentum transfer from the scattered $^3$He quasiparticles at the free\u0000surface. The scattering process of the quasiparticles is classified into the\u0000normal reflection and the Andreev retroreflection. Since the quasiparticles\u0000nearly conserve the momentum in the process of the Andreev retroreflection at\u0000the free surface, the Andreev reflected quasiparticles do not produce a\u0000resistive force to the Wigner solid. In this report, we have analytically\u0000calculated the contribution of the Andreev retroreflection to the mobility of\u0000the Wigner solid on superfluid $^3$He-B by employing a realistic model order\u0000parameter with the free surface. The Andreev retroreflection is lacked for\u0000quasiparticles with energy above the bulk energy gap under the model order\u0000parameter. Then, the Andreev retroreflection does not contribute to a rise in\u0000the mobility of the Wigner solid on the superfluid $^3$He-B. The present model\u0000calculation is in good agreement with the previous experimental observation. We\u0000have also discussed the Andreev retroreflection under a self-consistently\u0000calculated order parameter.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"42 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141500868","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}
Eric Bousquet, Mauro Fava, Zachary Romestan, Fernando Gómez-Ortiz, Emma E. McCabe, Aldo H. Romero
Chirality refers to the asymmetry of objects that cannot be superimposed on their mirror image. It is a concept that exists in various scientific fields and has profound consequences. Although these are perhaps most widely recognized within biology, chemistry, and pharmacology, recent advances in chiral phonons, topological systems, crystal enantiomorphic materials, and magneto-chiral materials have brought this topic to the forefront of condensed matter physics research. Our review discusses the symmetry requirements and the features associated with structural chirality in inorganic materials. This allows us to explore the nature of phase transitions in these systems, the coupling between order parameters, and their impact on the material's physical properties. We highlight essential contributions to the field, particularly recent progress in the study of chiral phonons, altermagnetism, magnetochirality between others. Despite the rarity of naturally occurring inorganic chiral crystals, this review also highlights a significant knowledge gap, presenting challenges and opportunities for structural chirality mostly at the fundamental level, e.g., chiral displacive phase transitions and ferrochirality, possibilities of tuning and switching structural chirality by external means (electric, magnetic, or strain fields), whether chirality could be an independent order parameter, and whether structural chirality could be quantified, etc. Beyond simply summarising this field of research, this review aims to inspire further research in materials science by addressing future challenges, encouraging the exploration of chirality beyond traditional boundaries, and seeking the development of innovative materials with superior or new properties.
{"title":"Structural chirality and related properties in the periodic inorganic solids: Review and perspectives","authors":"Eric Bousquet, Mauro Fava, Zachary Romestan, Fernando Gómez-Ortiz, Emma E. McCabe, Aldo H. Romero","doi":"arxiv-2406.14684","DOIUrl":"https://doi.org/arxiv-2406.14684","url":null,"abstract":"Chirality refers to the asymmetry of objects that cannot be superimposed on\u0000their mirror image. It is a concept that exists in various scientific fields\u0000and has profound consequences. Although these are perhaps most widely\u0000recognized within biology, chemistry, and pharmacology, recent advances in\u0000chiral phonons, topological systems, crystal enantiomorphic materials, and\u0000magneto-chiral materials have brought this topic to the forefront of condensed\u0000matter physics research. Our review discusses the symmetry requirements and the\u0000features associated with structural chirality in inorganic materials. This\u0000allows us to explore the nature of phase transitions in these systems, the\u0000coupling between order parameters, and their impact on the material's physical\u0000properties. We highlight essential contributions to the field, particularly\u0000recent progress in the study of chiral phonons, altermagnetism,\u0000magnetochirality between others. Despite the rarity of naturally occurring\u0000inorganic chiral crystals, this review also highlights a significant knowledge\u0000gap, presenting challenges and opportunities for structural chirality mostly at\u0000the fundamental level, e.g., chiral displacive phase transitions and\u0000ferrochirality, possibilities of tuning and switching structural chirality by\u0000external means (electric, magnetic, or strain fields), whether chirality could\u0000be an independent order parameter, and whether structural chirality could be\u0000quantified, etc. Beyond simply summarising this field of research, this review\u0000aims to inspire further research in materials science by addressing future\u0000challenges, encouraging the exploration of chirality beyond traditional\u0000boundaries, and seeking the development of innovative materials with superior\u0000or new properties.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141531576","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}
Among vortex structures identified so far in superfluid $^3$He-B, the most common are the A-phase-core vortex and the double-core vortex. According to earlier numerical calculations, the double-core vortex is energetically favored nearly everywhere in the $p$-$T$ phase diagram. Nevertheless, in experiments the A-phase-core vortex has been observed down to temperatures of $0.6T_{mathrm{c}}$ at high pressures. We use the Ginzburg-Landau formalism to calculate the energies of the two vortex structures in the experimentally relevant magnetic field as well as the energy barrier for the transition between the two structures. Assigning vanishing barrier as the boundary of the metastability region of the A-phase-core vortex, we reproduce the experimentally measured vortex phase diagram and provide an explanation for the reappearance of the double-core vortex near the critical temperature $T_{mathrm{c}}$ at low pressures: The difference in Zeeman energy between the two vortex structures becomes relatively more important close to $T_{mathrm{c}}$, and the A-phase-core vortex becomes unstable. In contrast to the equilibrium vortex structures, we suggest that the vortex nucleation process favors the A-phase-core vortex over the double-core vortex. Our approach can be used to analyze competition between different vortex structures in other unconventional superfluids and superconductors.
迄今为止，在超流体 $^3$He-B 中发现的漩涡结构中，最常见的是 A 相核漩涡和双核漩涡。根据早期的数值计算，在$p$-$T$相图中，双核漩涡在能量上几乎无处不在。尽管如此，在实验中我们还是观测到了在高压下温度低至$0.6T_{mathrm{c}}$的 A 相核漩涡。我们使用金兹堡-朗道（Ginzburg-Landau）形式主义来计算实验相关磁场中两种涡旋结构的能量，以及两种结构之间转变的能障。将消失势垒指定为 A 相核涡旋瞬变区的边界，我们再现了实验测量的涡旋相图，并解释了低压下临界温度$T_{mathrm{c}}$附近出现双核涡旋的原因：在接近$T_{mathrm{c}}$时，两种漩涡结构之间的泽曼能差异变得相对更重要，A相核漩涡变得不稳定。与平衡漩涡结构相比，我们认为漩涡成核过程更倾向于A相核漩涡，而不是双核漩涡。我们的方法可用于分析其他非常规超流体和超导体中不同涡旋结构之间的竞争。
{"title":"Competition of vortex core structures in superfluid $^3$He-B","authors":"Riku Rantanen, Vladimir Eltsov","doi":"arxiv-2406.13649","DOIUrl":"https://doi.org/arxiv-2406.13649","url":null,"abstract":"Among vortex structures identified so far in superfluid $^3$He-B, the most\u0000common are the A-phase-core vortex and the double-core vortex. According to\u0000earlier numerical calculations, the double-core vortex is energetically favored\u0000nearly everywhere in the $p$-$T$ phase diagram. Nevertheless, in experiments\u0000the A-phase-core vortex has been observed down to temperatures of\u0000$0.6T_{mathrm{c}}$ at high pressures. We use the Ginzburg-Landau formalism to\u0000calculate the energies of the two vortex structures in the experimentally\u0000relevant magnetic field as well as the energy barrier for the transition\u0000between the two structures. Assigning vanishing barrier as the boundary of the\u0000metastability region of the A-phase-core vortex, we reproduce the\u0000experimentally measured vortex phase diagram and provide an explanation for the\u0000reappearance of the double-core vortex near the critical temperature\u0000$T_{mathrm{c}}$ at low pressures: The difference in Zeeman energy between the\u0000two vortex structures becomes relatively more important close to\u0000$T_{mathrm{c}}$, and the A-phase-core vortex becomes unstable. In contrast to\u0000the equilibrium vortex structures, we suggest that the vortex nucleation\u0000process favors the A-phase-core vortex over the double-core vortex. Our\u0000approach can be used to analyze competition between different vortex structures\u0000in other unconventional superfluids and superconductors.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"154 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141531496","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}
Quantum spin Hall (QSH) insulators have attracted intensive experimental and theoretical studies due to their beneficial applications in spintronic devices. Density functional theory (DFT) meets challenges when describing the electronic structure of QSH materials. Only the Heyd-Scuseria-Ernzerhof (HSE06) with spin-orbit coupling (SOC) is effective in revealing the band opening in the typical QSH 1T`-WTe2, but with increased computational demands. Here, using DFT, Wannier function simulations, the screened hybrid HSE06 functional, and first-principles-based many body perturbation theory GW, we investigate the sensitive electronic structure in monolayer 1T`-WTe2, with advanced meta-generalized gradient (meta-GGA) density functional approximations. The success of the recent SCAN and r2SCAN meta-GGAs left their predecessor meta-GGA made very simple (MVS) ignored by the scientific community. Largely unnoticed were the increased band gaps of MVS compared to any semilocal approximation including SCAN. We find that the non-empirical MVS approximation yields a positive fundamental band gap, without any help from exact exchange, Hubbard U, or SOC correction. We explain the success of the meta-GGA MVS for the band gap in 1T`-WTe2 by presenting two working mechanisms in meta-GGA approximations. Besides, we point out the difficulty of using G0W0 for 1T`-WTe2. Although the single shot GW correction with an MVS reference yields a smaller band gap than GW with PBE, the G0W0@MVS is still not suitable for simulating 1T`-WTe2, due to its negative band gap. These DFT and beyond DFT results highlight the importance of meta-GGAs and novel construction schemes with enhanced kinetic energy density dependence. The MVS approximation re-appears as an appealing alternative for accurately describing 1T`-WTe2, paving an efficient way for exploring other two-dimensional QSH materials in high-throughput calculations.
{"title":"Inside the Working Mechanism of Meta-generalized Gradient Density Functional Approximations: The Example of Quantum Spin-Hall Insulator 1T`-WTe2","authors":"Li Yin, Hong Tang, Adrienn Ruzsinszky","doi":"arxiv-2406.12124","DOIUrl":"https://doi.org/arxiv-2406.12124","url":null,"abstract":"Quantum spin Hall (QSH) insulators have attracted intensive experimental and\u0000theoretical studies due to their beneficial applications in spintronic devices.\u0000Density functional theory (DFT) meets challenges when describing the electronic\u0000structure of QSH materials. Only the Heyd-Scuseria-Ernzerhof (HSE06) with\u0000spin-orbit coupling (SOC) is effective in revealing the band opening in the\u0000typical QSH 1T`-WTe2, but with increased computational demands. Here, using\u0000DFT, Wannier function simulations, the screened hybrid HSE06 functional, and\u0000first-principles-based many body perturbation theory GW, we investigate the\u0000sensitive electronic structure in monolayer 1T`-WTe2, with advanced\u0000meta-generalized gradient (meta-GGA) density functional approximations. The\u0000success of the recent SCAN and r2SCAN meta-GGAs left their predecessor meta-GGA\u0000made very simple (MVS) ignored by the scientific community. Largely unnoticed\u0000were the increased band gaps of MVS compared to any semilocal approximation\u0000including SCAN. We find that the non-empirical MVS approximation yields a\u0000positive fundamental band gap, without any help from exact exchange, Hubbard U,\u0000or SOC correction. We explain the success of the meta-GGA MVS for the band gap\u0000in 1T`-WTe2 by presenting two working mechanisms in meta-GGA approximations.\u0000Besides, we point out the difficulty of using G0W0 for 1T`-WTe2. Although the\u0000single shot GW correction with an MVS reference yields a smaller band gap than\u0000GW with PBE, the G0W0@MVS is still not suitable for simulating 1T`-WTe2, due to\u0000its negative band gap. These DFT and beyond DFT results highlight the\u0000importance of meta-GGAs and novel construction schemes with enhanced kinetic\u0000energy density dependence. The MVS approximation re-appears as an appealing\u0000alternative for accurately describing 1T`-WTe2, paving an efficient way for\u0000exploring other two-dimensional QSH materials in high-throughput calculations.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"37 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141531455","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}
Pasquale Mastrovito, Halima Giovanna Ahmad, Martina Esposito, Davide Massarotti, Francesco Tafuri
Coherent photon sources are key elements in different applications, ranging from quantum sensing to quantum computing. In the context of circuit quantum electrodynamics, there have been multiple proposals for potential coherent sources of photons, but a well established candidate is still missing. The possibility of designing and engineering superconducting circuits behaving like artificial atoms supports the realization of quantum optics protocols, including microwave photons generation. Here we propose and theoretically investigate a new design that allows a tunable photon injection directly on-chip. The scheme is based on initiating a population inversion in a superconducting circuit that will act as the photon source of one or multiple target resonators. The key novelty of the proposed layout consists in replacing the usual capacitive link between the source and the target cavity with a tunable coupler, with the advantage of having on-demand control on the injected steady-state photons. We validate the dynamical control of the generated coherent states under the effect of an external flux threading the tunable coupler and discuss the possibility of employing this scheme also in the context of multiple bosonic reservoirs.
{"title":"On-chip microwave coherent source with in-situ control of the photon number distribution","authors":"Pasquale Mastrovito, Halima Giovanna Ahmad, Martina Esposito, Davide Massarotti, Francesco Tafuri","doi":"arxiv-2406.10597","DOIUrl":"https://doi.org/arxiv-2406.10597","url":null,"abstract":"Coherent photon sources are key elements in different applications, ranging\u0000from quantum sensing to quantum computing. In the context of circuit quantum\u0000electrodynamics, there have been multiple proposals for potential coherent\u0000sources of photons, but a well established candidate is still missing. The\u0000possibility of designing and engineering superconducting circuits behaving like\u0000artificial atoms supports the realization of quantum optics protocols,\u0000including microwave photons generation. Here we propose and theoretically\u0000investigate a new design that allows a tunable photon injection directly\u0000on-chip. The scheme is based on initiating a population inversion in a\u0000superconducting circuit that will act as the photon source of one or multiple\u0000target resonators. The key novelty of the proposed layout consists in replacing\u0000the usual capacitive link between the source and the target cavity with a\u0000tunable coupler, with the advantage of having on-demand control on the injected\u0000steady-state photons. We validate the dynamical control of the generated\u0000coherent states under the effect of an external flux threading the tunable\u0000coupler and discuss the possibility of employing this scheme also in the\u0000context of multiple bosonic reservoirs.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141531456","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}
Understanding the correlation between fast and ultrafast demagnetization processes is crucial for elucidating the microscopic mechanisms underlying ultrafast demagnetization, which is pivotal for various applications in spintronics. Initial theoretical models attempted to establish this correlation but faced challenges due to the complex interplay of physical phenomena. To address this, we employed a variety of machine learning methods, including supervised learning regression algorithms and symbolic regression, to analyze limited experimental data and derive meaningful mathematical expressions between demagnetization time and the Gilbert damping factor. The results reveal that polynomial regression and K-nearest neighbors algorithms perform best in predicting demagnetization time. Additionally, sure-independence-screening-and-sparsifying-operator (SISSO) as a symbolic regression method suggested a direct correlation between demagnetization time and damping factor for Ni and Ni80Fe20, indicating spin-flip scattering predominantly influences the ultrafast demagnetization mechanism. The developed models demonstrate promising predictive capabilities, validated against independent experimental data. Comparative analysis between different materials underscores the significant impact of material properties on ultrafast demagnetization behavior. This study underscores the potential of machine learning in unraveling complex physical phenomena and offers valuable insights for future research in ultrafast magnetism.
了解快速和超快退磁过程之间的相关性对于阐明超快退磁的微观机制至关重要，而超快退磁对于电子学的各种应用至关重要。最初的理论模型试图建立这种相关性，但由于物理现象之间复杂的相互作用而面临挑战。为了解决这个问题，我们采用了多种机器学习方法，包括监督学习回归算法和符号回归，来分析有限的实验数据，并推导出消磁时间与吉尔伯特阻尼因子之间有意义的数学表达式。结果表明，多项式回归和 K 最近邻算法在预测退磁时间方面表现最佳。此外，作为符号回归方法的确定不依赖性筛选和解析操作器（SISSO）表明，Ni 和 Ni80Fe20 的退磁时间和阻尼因子之间存在直接相关性，这表明自旋翻转散射主要影响超快退磁机制。所开发的模型与独立的实验数据进行了验证，显示出良好的预测能力。不同材料之间的对比分析表明了材料特性对超快退磁行为的重要影响。这项研究强调了机器学习在揭示复杂物理现象方面的潜力，并为未来的超快磁研究提供了宝贵的见解。
{"title":"Applying Machine Learning to Elucidate Ultrafast Demagnetization Dynamics in Ni and Ni80Fe20","authors":"Hasan Ahmadian Baghbaderani, Byoung-Chul Choi","doi":"arxiv-2406.09620","DOIUrl":"https://doi.org/arxiv-2406.09620","url":null,"abstract":"Understanding the correlation between fast and ultrafast demagnetization\u0000processes is crucial for elucidating the microscopic mechanisms underlying\u0000ultrafast demagnetization, which is pivotal for various applications in\u0000spintronics. Initial theoretical models attempted to establish this correlation\u0000but faced challenges due to the complex interplay of physical phenomena. To\u0000address this, we employed a variety of machine learning methods, including\u0000supervised learning regression algorithms and symbolic regression, to analyze\u0000limited experimental data and derive meaningful mathematical expressions\u0000between demagnetization time and the Gilbert damping factor. The results reveal\u0000that polynomial regression and K-nearest neighbors algorithms perform best in\u0000predicting demagnetization time. Additionally,\u0000sure-independence-screening-and-sparsifying-operator (SISSO) as a symbolic\u0000regression method suggested a direct correlation between demagnetization time\u0000and damping factor for Ni and Ni80Fe20, indicating spin-flip scattering\u0000predominantly influences the ultrafast demagnetization mechanism. The developed\u0000models demonstrate promising predictive capabilities, validated against\u0000independent experimental data. Comparative analysis between different materials\u0000underscores the significant impact of material properties on ultrafast\u0000demagnetization behavior. This study underscores the potential of machine\u0000learning in unraveling complex physical phenomena and offers valuable insights\u0000for future research in ultrafast magnetism.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141500869","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}
The control of the spin degree of freedom is at the heart of spintronics, which can potentially be achieved by spin-orbit coupling or band topological effects. In this paper, we explore another potential controlled mechanism under debate: the spin-deformation coupling (SDC) - the coupling between intrinsic or extrinsic geometrical deformations and the spin degree of freedom. We focus on polar-deformed thin films or two-dimensional compounds, where the Rashba spin-orbit coupling (SOC) is considered as an $SU(2)$ non-Abelian gauge field. We demonstrate that the dynamics between surface and normal electronic degrees of freedom can be properly decoupled using the thin-layer approach by performing a suitable gauge transformation, as introduced in the context of many-body correlated systems. Our work leads to three significant results: (i) gauge invariance implies that the spin is uncoupled from the surface's extrinsic geometry, challenging the common consensus; (ii) the Rashba SOC on a curved surface can be included as an $SU(2)$ non-Abelian gauge field in curvilinear coordinates; and (iii) we identify a previously unnoticed scalar geometrical potential dependent on the Rashba SOC strength. This scalar potential, independent of spin, represents the residual effect remaining after decoupling the normal component of the non-Abelian gauge field. The outcomes of our work open novel pathways for exploring the manipulation of spin degrees of freedom through the use of the SDC.
{"title":"Spin-deformation coupling in two-dimensional polar materials","authors":"J. A. Sánchez-Monroy, Carlos Mera Acosta","doi":"arxiv-2406.09599","DOIUrl":"https://doi.org/arxiv-2406.09599","url":null,"abstract":"The control of the spin degree of freedom is at the heart of spintronics,\u0000which can potentially be achieved by spin-orbit coupling or band topological\u0000effects. In this paper, we explore another potential controlled mechanism under\u0000debate: the spin-deformation coupling (SDC) - the coupling between intrinsic or\u0000extrinsic geometrical deformations and the spin degree of freedom. We focus on\u0000polar-deformed thin films or two-dimensional compounds, where the Rashba\u0000spin-orbit coupling (SOC) is considered as an $SU(2)$ non-Abelian gauge field.\u0000We demonstrate that the dynamics between surface and normal electronic degrees\u0000of freedom can be properly decoupled using the thin-layer approach by\u0000performing a suitable gauge transformation, as introduced in the context of\u0000many-body correlated systems. Our work leads to three significant results: (i)\u0000gauge invariance implies that the spin is uncoupled from the surface's\u0000extrinsic geometry, challenging the common consensus; (ii) the Rashba SOC on a\u0000curved surface can be included as an $SU(2)$ non-Abelian gauge field in\u0000curvilinear coordinates; and (iii) we identify a previously unnoticed scalar\u0000geometrical potential dependent on the Rashba SOC strength. This scalar\u0000potential, independent of spin, represents the residual effect remaining after\u0000decoupling the normal component of the non-Abelian gauge field. The outcomes of\u0000our work open novel pathways for exploring the manipulation of spin degrees of\u0000freedom through the use of the SDC.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"63 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141520113","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}
While the transition between skyrmionic and non-topological states has been widely explored as a bit operation for information transport and storage in spintronic devices, the ultrafast dynamics of such transitions remains challenging to observe and understand. Here, we utilize spin-dynamics simulations and harmonic transition state theory (HTST) to provide an in-depth analysis of the nucleation of skyrmionic states in helimagnets. We reveal a persistent blinking (creation-annihilation) phenomenon of these topological states under specific conditions near the phase boundary between skyrmion and conical states. Through a minimum-energy path analysis, we elucidate that this blinking behavior is favored by the formation of chiral bobber (CB) surface states and that the collapse of CBs differs from that of skyrmions in thin films due to their different oscillation modes. We further employ HTST to estimate the typical blinking time as a function of the applied magnetic field and temperature. Finally, we illustrate the practical use of skyrmion blinking for controlled probabilistic computing, exemplified by a skyrmion-based random-number generator.
{"title":"Skyrmion blinking from the conical phase","authors":"Rai M. Menezes, Milorad V. Milosevic","doi":"arxiv-2406.08230","DOIUrl":"https://doi.org/arxiv-2406.08230","url":null,"abstract":"While the transition between skyrmionic and non-topological states has been\u0000widely explored as a bit operation for information transport and storage in\u0000spintronic devices, the ultrafast dynamics of such transitions remains\u0000challenging to observe and understand. Here, we utilize spin-dynamics\u0000simulations and harmonic transition state theory (HTST) to provide an in-depth\u0000analysis of the nucleation of skyrmionic states in helimagnets. We reveal a\u0000persistent blinking (creation-annihilation) phenomenon of these topological\u0000states under specific conditions near the phase boundary between skyrmion and\u0000conical states. Through a minimum-energy path analysis, we elucidate that this\u0000blinking behavior is favored by the formation of chiral bobber (CB) surface\u0000states and that the collapse of CBs differs from that of skyrmions in thin\u0000films due to their different oscillation modes. We further employ HTST to\u0000estimate the typical blinking time as a function of the applied magnetic field\u0000and temperature. Finally, we illustrate the practical use of skyrmion blinking\u0000for controlled probabilistic computing, exemplified by a skyrmion-based\u0000random-number generator.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"35 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141520114","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}
In this work, we prescribe a theoretical framework aiming at predicting the position of monovacancy defects at the edges of zigzag graphene nanoribbons (ZGNRs) using Floquet-Bloch formalism, which can be experimentally observed through time- and angle-resolved photoemission spectroscopy (tr-ARPES). Our methodology involves an in-depth investigation of the Floquet quasienergy band spectrum influenced by light with varying polarization across a range of frequencies. Particularly under the influence of circularly polarized light with a frequency comparable to the bandwidth of the system, our findings suggest a promising approach for locating monovacancy defects at either edge, a challenge that proves intricate to predict from the ARPES spectrum of ZGNRs with monovacancy defects. This has been achieved by analyzing the orientation of the Floquet edge state and the appearance of new Dirac points in the vicinity of the Fermi level. The real-world applications of these captivating characteristics underscore the importance and pertinence of our theoretical framework, paving the way for additional exploration and practical use. Our approach, employing the Floquet formalism, is not limited to monovacancy-type defects; rather, it can be expanded to encompass various types of vacancy defects.
{"title":"Predicting edge-localized monovacancy defects in zigzag graphene nanoribbons from Floquet quasienergy spectrum","authors":"Gulshan Kumar, Shashikant Kumar, Ajay Kumar, Prakash Parida","doi":"arxiv-2406.05643","DOIUrl":"https://doi.org/arxiv-2406.05643","url":null,"abstract":"In this work, we prescribe a theoretical framework aiming at predicting the\u0000position of monovacancy defects at the edges of zigzag graphene nanoribbons\u0000(ZGNRs) using Floquet-Bloch formalism, which can be experimentally observed\u0000through time- and angle-resolved photoemission spectroscopy (tr-ARPES). Our\u0000methodology involves an in-depth investigation of the Floquet quasienergy band\u0000spectrum influenced by light with varying polarization across a range of\u0000frequencies. Particularly under the influence of circularly polarized light\u0000with a frequency comparable to the bandwidth of the system, our findings\u0000suggest a promising approach for locating monovacancy defects at either edge, a\u0000challenge that proves intricate to predict from the ARPES spectrum of ZGNRs\u0000with monovacancy defects. This has been achieved by analyzing the orientation\u0000of the Floquet edge state and the appearance of new Dirac points in the\u0000vicinity of the Fermi level. The real-world applications of these captivating\u0000characteristics underscore the importance and pertinence of our theoretical\u0000framework, paving the way for additional exploration and practical use. Our\u0000approach, employing the Floquet formalism, is not limited to monovacancy-type\u0000defects; rather, it can be expanded to encompass various types of vacancy\u0000defects.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141520115","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}
Ultrafast laser radiation or beams of fast charged particles primarily excite the electronic system of a solid target driving it transiently out of thermal equilibrium. Apart from the nonequilibrium between the electrons and atoms, each of the subsystems may themselves be far from equilibrium. We demonstrate that the transient state of the atomic system may be tracked with the generalized temperature approach in the configuration and momentum subspaces. It is shown that the definition of the kinetic temperature of atoms in the momentum subspace is unaffected by the excitation of the electronic system. We derive an expression for the configurational atomic temperature when the electronic temperature differs from the atomic one, applicable to the electronic-temperature-dependent interatomic potentials (such as ab-initio molecular dynamics simulations). It is revealed that upon ultrafast irradiation, the atomic system of a solid exists temporarily in a multi-temperature state: separate equilibria in the momentum and configurational subspaces. Complete equilibration between the various atomic temperatures takes place at longer timescales, forming the energy equipartition. Based on these results, we propose a formulation of multi-temperature heat transport equations.
{"title":"Multi-temperature atomic ensemble: nonequilibrium evolution after ultrafast electronic excitation","authors":"Nikita Medvedev, Alexander E. Volkov","doi":"arxiv-2406.05718","DOIUrl":"https://doi.org/arxiv-2406.05718","url":null,"abstract":"Ultrafast laser radiation or beams of fast charged particles primarily excite\u0000the electronic system of a solid target driving it transiently out of thermal\u0000equilibrium. Apart from the nonequilibrium between the electrons and atoms,\u0000each of the subsystems may themselves be far from equilibrium. We demonstrate\u0000that the transient state of the atomic system may be tracked with the\u0000generalized temperature approach in the configuration and momentum subspaces.\u0000It is shown that the definition of the kinetic temperature of atoms in the\u0000momentum subspace is unaffected by the excitation of the electronic system. We\u0000derive an expression for the configurational atomic temperature when the\u0000electronic temperature differs from the atomic one, applicable to the\u0000electronic-temperature-dependent interatomic potentials (such as ab-initio\u0000molecular dynamics simulations). It is revealed that upon ultrafast\u0000irradiation, the atomic system of a solid exists temporarily in a\u0000multi-temperature state: separate equilibria in the momentum and\u0000configurational subspaces. Complete equilibration between the various atomic\u0000temperatures takes place at longer timescales, forming the energy\u0000equipartition. Based on these results, we propose a formulation of\u0000multi-temperature heat transport equations.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"190 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141500870","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}
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