The Klein bottle Benalcazar-Bernevig-Hughes (BBH) insulator phase plays a pivotal role in understanding higher-order topological phases. The insulator phase is characterized by a unique feature: a nonsymmorphic glide symmetry that exists within momentum space, rather than real space. This characteristic transforms the Brillouin zone's fundamental domain into a structure of Klein bottle. Here, we report an observation of a Klein bottle topoelectrical model under gauge fields. To provide a comprehensive understanding of the different corner distributions of odd and even unit cells, we present theoretical calculations and demonstrate that the symmetry properties significantly affect the topological nature. These theoretical predictions are confirmed by experimental results, which demonstrate the practical feasibility of such topological configurations in electronic circuits. Our work establishes a vital connection between the realms of condensed matter physics and circuit systems, thereby paving a pathway for investigating exotic condensed matter physics.
{"title":"Observation of Klein bottle quadrupole topological insulators in electric circuits","authors":"Xizhou Shen, Keyu Pan, Xiumei Wang, Xingping Zhou","doi":"arxiv-2407.07470","DOIUrl":"https://doi.org/arxiv-2407.07470","url":null,"abstract":"The Klein bottle Benalcazar-Bernevig-Hughes (BBH) insulator phase plays a\u0000pivotal role in understanding higher-order topological phases. The insulator\u0000phase is characterized by a unique feature: a nonsymmorphic glide symmetry that\u0000exists within momentum space, rather than real space. This characteristic\u0000transforms the Brillouin zone's fundamental domain into a structure of Klein\u0000bottle. Here, we report an observation of a Klein bottle topoelectrical model\u0000under gauge fields. To provide a comprehensive understanding of the different\u0000corner distributions of odd and even unit cells, we present theoretical\u0000calculations and demonstrate that the symmetry properties significantly affect\u0000the topological nature. These theoretical predictions are confirmed by\u0000experimental results, which demonstrate the practical feasibility of such\u0000topological configurations in electronic circuits. Our work establishes a vital\u0000connection between the realms of condensed matter physics and circuit systems,\u0000thereby paving a pathway for investigating exotic condensed matter physics.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"37 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141588079","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}
Archit Dhingra, Mohammad Zaid Zaz, Peter A. Dowben
Spin crossover (SCO) complexes are highly promising candidates for a myriad of potential applications in room-temperature electronics; however, as it stands, establishing a clear connection between their spin-state switching and transport properties has been far from trivial. In this Viewpoint, an effort to unravel the underlying charge transport mechanism in these SCO complexes, via a general theory, is made. The theory presented herein is aimed at providing a unifying picture that explains the widely different trends observed in the spin-crossover-dependent carrier transport properties in the SCO molecular thin film systems.
{"title":"An All-encompassing Theory on Charge Transport in Spin Crossover Complexes","authors":"Archit Dhingra, Mohammad Zaid Zaz, Peter A. Dowben","doi":"arxiv-2407.17517","DOIUrl":"https://doi.org/arxiv-2407.17517","url":null,"abstract":"Spin crossover (SCO) complexes are highly promising candidates for a myriad\u0000of potential applications in room-temperature electronics; however, as it\u0000stands, establishing a clear connection between their spin-state switching and\u0000transport properties has been far from trivial. In this Viewpoint, an effort to\u0000unravel the underlying charge transport mechanism in these SCO complexes, via a\u0000general theory, is made. The theory presented herein is aimed at providing a\u0000unifying picture that explains the widely different trends observed in the\u0000spin-crossover-dependent carrier transport properties in the SCO molecular thin\u0000film systems.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141784200","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}
D. Lagarde, M. Glazov, V. Jindal, K. Mourzidis, Iann Gerber, A. Balocchi, L. Lombez, P. Renucci, T. Taniguchi, K. Watanabe, C. Robert, X. Marie
In transition metal dichalcogenide semiconductor monolayers the spin dynamics of electrons is controlled by the original spin-valley locking effect resulting from the interplay between spin-orbit interaction and inversion asymmetry. As a consequence, for electrons occupying bottom conduction bands, a carrier spin flip occurs only if there is a simultaneous change of valley. However, very little is known about the intra-valley spin relaxation processes. In this work we have performed stationary and time-resolved photoluminescence measurements in high quality WSe$_2$ monolayers. Our experiments highlight an efficient relaxation from bright to dark excitons, due to a fast intra-valley electron transfer from the top to the bottom conduction band with opposite spins. A combination of experiments and theoretical analysis allows us to infer a spin relaxation time of about $tau_ssim10~$ps, driven by the interplay between $Gamma$-valley chiral phonons and spin-orbit mixing.
{"title":"Efficient Electron Spin Relaxation by Chiral Phonons in WSe$_2$ Monolayers","authors":"D. Lagarde, M. Glazov, V. Jindal, K. Mourzidis, Iann Gerber, A. Balocchi, L. Lombez, P. Renucci, T. Taniguchi, K. Watanabe, C. Robert, X. Marie","doi":"arxiv-2407.07188","DOIUrl":"https://doi.org/arxiv-2407.07188","url":null,"abstract":"In transition metal dichalcogenide semiconductor monolayers the spin dynamics\u0000of electrons is controlled by the original spin-valley locking effect resulting\u0000from the interplay between spin-orbit interaction and inversion asymmetry. As a\u0000consequence, for electrons occupying bottom conduction bands, a carrier spin\u0000flip occurs only if there is a simultaneous change of valley. However, very\u0000little is known about the intra-valley spin relaxation processes. In this work\u0000we have performed stationary and time-resolved photoluminescence measurements\u0000in high quality WSe$_2$ monolayers. Our experiments highlight an efficient\u0000relaxation from bright to dark excitons, due to a fast intra-valley electron\u0000transfer from the top to the bottom conduction band with opposite spins. A\u0000combination of experiments and theoretical analysis allows us to infer a spin\u0000relaxation time of about $tau_ssim10~$ps, driven by the interplay between\u0000$Gamma$-valley chiral phonons and spin-orbit mixing.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"37 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141588078","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}
Pawel Strak, Pawel Kempisty, Konrad Sakowski, Jacek Piechota, Izabella Grzegory, Eva Monroy, Agata Kaminska, Stanislaw Krukowski
Fundamental properties of spontaneous and piezo polarization are reformulated and critically reviewed. It was demonstrated that Landau definition of polarization as a dipole density could be used to the infinite systems. The difference between the bulk polarization and surface polarity are distinguished thus creating clear identification of both components. The local model of spontaneous polarization was created and used to calculate spontaneous polarization as the electric dipole density. It was shown that the proposed local model correctly predicts c-axis spontaneous polarization values of the nitride wurtzite semiconductors. It was also shown that the proposed model predicts zero polarization in the plane perpendicular to the c-axis, in accordance with symmetry requirements. In addition, the model results are in accordance with polarization equal to zero for zinc blende lattice. These data confirm the basic correctness of the proposed model. The spontaneous polarization values obtained for all wurtzite III nitrides (BN, AlN, GaN and InN) are in basic agreement with the earlier calculations using Berry phase and slab models of Bernardini et al. {Bernardini et al. Phys Rev B 56 (2001) R10024 & 63 (2001) 193201} but not with Dreyer et al. {Dreyer et al. Phys. Rev X 6 (2016) 021038}. Wurtzite nitride superlattices ab initio calculations were performed to derive polarization-induced fields in the coherently strained lattices showing good agreement with the polarization values. The strained superlattice data were used to determine the piezoelectric parameters of wurtzite nitrides obtaining the values that were in basic agreement with the earlier data. Zinc blende superlattices were also modeled using ab initio calculations showing results that are in agreement with the absence of polarization of all nitrides in zinc blende symmetry.
对自发极化和压电极化的基本特性进行了重新表述和批判性评述。研究证明，作为偶极子密度的极化的朗道定义可用于无限系统。区分了体极化和表面极性之间的差异，从而清晰地识别了这两种成分。创建了自发极化的局部模型，并将其用于计算作为电偶极子密度的自发极化。结果表明，所提出的局部模型能正确预测氮化物晶格半导体的 c 轴自发极化值。研究还表明，所提出的模型在垂直于 c 轴的平面上预测的极化值为零，不符合对称性要求。此外，模型结果与锌掺杂晶格的极化等于零也不一致。这些数据证实了所提模型的基本正确性。所有钝方三氮化物（BN、AlN、GaN 和 InN）的自发极化值都与 Bernardini 等人早先使用贝里相和片模型{Bernardini et al. Phys Rev B 56 (2001) R10024& 63 (2001) 193201}的计算结果基本一致，但与 Dreyer 等人{Dreyer et al. Phys. Rev X 6(2016) 021038}的计算结果不一致。为了推导相干应变晶格中的极化诱导场，我们进行了伍兹氮化物超晶格 ab initio 计算，结果显示与极化值非常吻合。利用应变超晶格数据确定了钨氮化物的压电参数，得到的数值与先前的数据基本一致。此外，还使用 ab initiocalculations 对锌混合物超晶格进行了建模，结果表明与锌混合物对称的所有氮化物都不存在极化现象相一致。
{"title":"Polarization spontaneous and piezo: fundamentals and their implementation in ab initio calculations","authors":"Pawel Strak, Pawel Kempisty, Konrad Sakowski, Jacek Piechota, Izabella Grzegory, Eva Monroy, Agata Kaminska, Stanislaw Krukowski","doi":"arxiv-2407.01134","DOIUrl":"https://doi.org/arxiv-2407.01134","url":null,"abstract":"Fundamental properties of spontaneous and piezo polarization are reformulated\u0000and critically reviewed. It was demonstrated that Landau definition of\u0000polarization as a dipole density could be used to the infinite systems. The\u0000difference between the bulk polarization and surface polarity are distinguished\u0000thus creating clear identification of both components. The local model of\u0000spontaneous polarization was created and used to calculate spontaneous\u0000polarization as the electric dipole density. It was shown that the proposed\u0000local model correctly predicts c-axis spontaneous polarization values of the\u0000nitride wurtzite semiconductors. It was also shown that the proposed model\u0000predicts zero polarization in the plane perpendicular to the c-axis, in\u0000accordance with symmetry requirements. In addition, the model results are in\u0000accordance with polarization equal to zero for zinc blende lattice. These data\u0000confirm the basic correctness of the proposed model. The spontaneous\u0000polarization values obtained for all wurtzite III nitrides (BN, AlN, GaN and\u0000InN) are in basic agreement with the earlier calculations using Berry phase and\u0000slab models of Bernardini et al. {Bernardini et al. Phys Rev B 56 (2001) R10024\u0000& 63 (2001) 193201} but not with Dreyer et al. {Dreyer et al. Phys. Rev X 6\u0000(2016) 021038}. Wurtzite nitride superlattices ab initio calculations were\u0000performed to derive polarization-induced fields in the coherently strained\u0000lattices showing good agreement with the polarization values. The strained\u0000superlattice data were used to determine the piezoelectric parameters of\u0000wurtzite nitrides obtaining the values that were in basic agreement with the\u0000earlier data. Zinc blende superlattices were also modeled using ab initio\u0000calculations showing results that are in agreement with the absence of\u0000polarization of all nitrides in zinc blende symmetry.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141500866","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}
Rohit Pratyush Behera, Matthew Jun-Hui Reavley, Zehui Du, Gan Chee Lip, Hortense Le Ferrand
Crystallographic texture engineering in ceramics is essential to achieve direction-specific properties. Current texture engineering methods are time-consuming, energy extensive, or can lead to unnecessary diffusion of added dopants. Herein, we explore ultrafast high-temperature sintering (UHS) to prepare dense and textured alumina using templated grain growth (TGG). From a slurry containing alumina microplatelets coated with Fe3O4 nanoparticles dispersed in a matrix of alumina nanoparticles, green bodies with oriented microplatelets were prepared using magnetic assisted slip casting (MASC). The effects of the sintering temperature, time and heating rate on the density and microstructure of the obtained ceramics were then studied. We found that TGG occurs for a temperature range between 1640 and 1780 {deg}C and 10 s sintering time. Sintering at 1700 {deg}C for 10 s led to dense and textured alumina with anisotropic grains thanks to the Fe3O4 coating, which did not have the time to diffuse. The highest texture and relative density were obtained with a heating rate of ~5,500 {deg}C/min, leading to texture-dependent anisotropic mechanical properties. This study opens new avenues for fabricating textured ceramics in ultra-short times.
{"title":"Ultrafast high-temperature sintering of dense and textured alumina","authors":"Rohit Pratyush Behera, Matthew Jun-Hui Reavley, Zehui Du, Gan Chee Lip, Hortense Le Ferrand","doi":"arxiv-2407.00255","DOIUrl":"https://doi.org/arxiv-2407.00255","url":null,"abstract":"Crystallographic texture engineering in ceramics is essential to achieve\u0000direction-specific properties. Current texture engineering methods are\u0000time-consuming, energy extensive, or can lead to unnecessary diffusion of added\u0000dopants. Herein, we explore ultrafast high-temperature sintering (UHS) to\u0000prepare dense and textured alumina using templated grain growth (TGG). From a\u0000slurry containing alumina microplatelets coated with Fe3O4 nanoparticles\u0000dispersed in a matrix of alumina nanoparticles, green bodies with oriented\u0000microplatelets were prepared using magnetic assisted slip casting (MASC). The\u0000effects of the sintering temperature, time and heating rate on the density and\u0000microstructure of the obtained ceramics were then studied. We found that TGG\u0000occurs for a temperature range between 1640 and 1780 {deg}C and 10 s sintering\u0000time. Sintering at 1700 {deg}C for 10 s led to dense and textured alumina with\u0000anisotropic grains thanks to the Fe3O4 coating, which did not have the time to\u0000diffuse. The highest texture and relative density were obtained with a heating\u0000rate of ~5,500 {deg}C/min, leading to texture-dependent anisotropic mechanical\u0000properties. This study opens new avenues for fabricating textured ceramics in\u0000ultra-short times.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"167 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141520110","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}
Chris Reinhoffer, Ilya Razdolski, Philipp Stein, Semyon Germanskiy, Andrzej Stupakiewicz, Paul H. M. van Loosdrecht, Evgeny A. Mashkovich
The interaction of terahertz (THz) radiation with high-frequency spin resonances in complex magnetic materials is central for modern ultrafast magnonics. Here we demonstrate strong variations of the excitation efficiency of the sub-THz exchange magnon in a single crystal ferrimagnet (Gd,Bi)$_3$Fe$_5$O$_{12}$. An enhancement of the exchange magnon amplitude is observed when its frequency matches an eigenmode of the cavity created by the sample interfaces. Moreover, this enhancement is accompanied by a 5-fold decrease in effective damping of the exchange mode. The THz-exchange magnon interaction in the cavity is analyzed within the developed Landau-Lifshitz-Gilbert formalism for three coupled magnetization sublattices and cavity-enhanced THz field. This work presents a novel approach for the THz excitation of spin dynamics in ferrimagnets and outlines promising pathways for the controlled optimization of light-spin coupling in single crystals.
{"title":"THz Control of Exchange Mode in a Ferrimagnetic Cavity","authors":"Chris Reinhoffer, Ilya Razdolski, Philipp Stein, Semyon Germanskiy, Andrzej Stupakiewicz, Paul H. M. van Loosdrecht, Evgeny A. Mashkovich","doi":"arxiv-2406.19849","DOIUrl":"https://doi.org/arxiv-2406.19849","url":null,"abstract":"The interaction of terahertz (THz) radiation with high-frequency spin\u0000resonances in complex magnetic materials is central for modern ultrafast\u0000magnonics. Here we demonstrate strong variations of the excitation efficiency\u0000of the sub-THz exchange magnon in a single crystal ferrimagnet\u0000(Gd,Bi)$_3$Fe$_5$O$_{12}$. An enhancement of the exchange magnon amplitude is\u0000observed when its frequency matches an eigenmode of the cavity created by the\u0000sample interfaces. Moreover, this enhancement is accompanied by a 5-fold\u0000decrease in effective damping of the exchange mode. The THz-exchange magnon\u0000interaction in the cavity is analyzed within the developed\u0000Landau-Lifshitz-Gilbert formalism for three coupled magnetization sublattices\u0000and cavity-enhanced THz field. This work presents a novel approach for the THz\u0000excitation of spin dynamics in ferrimagnets and outlines promising pathways for\u0000the controlled optimization of light-spin coupling in single crystals.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"237 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141520111","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}
Bo Lv, Shiyun Xia, Ye Tian, Ting Liu, Hongyang Mu, Zhichao Shen, Sijie Wang, Zheng Zhu, Huibin Tao, Fanyi Meng, Jinhui Shi
The period-doubling oscillation emerges with the coexistence between zero and {pi} modes in Floquet topological insulator. Here, utilized the flexibility of the circuit, we construct the Floquet circuit with frequency-synthetic dimension and find the topological-protected deeply-subharmonic oscillations with the period extensively exceeding the doubling-driven period. In the construction framework, the periodically-driven mechanism is attained by implementing the circuit-oscillator hierarchy with the stepping-variation resonances in frequency domain. The zero and {pi} modes that arise at the Floquet band in the circuit indicate the anomalous boundary-bulk correspondence. The coexistence of zero and {pi} modes, results in a subharmonic oscillation with the extremely-low frequency on the edge of the Floquet circuit. Furthermore, we explore the Floquet band with the enhanced periodically-driven strength tailored by the component flexibility of the circuit. Our method provides a flexible scheme to study Floquet topological phases, and open a new path for realizing the deeply subwavelength system.
{"title":"Subharmonic oscillations in the Floquet circuit with the frequency-synthesis dimension","authors":"Bo Lv, Shiyun Xia, Ye Tian, Ting Liu, Hongyang Mu, Zhichao Shen, Sijie Wang, Zheng Zhu, Huibin Tao, Fanyi Meng, Jinhui Shi","doi":"arxiv-2406.18769","DOIUrl":"https://doi.org/arxiv-2406.18769","url":null,"abstract":"The period-doubling oscillation emerges with the coexistence between zero and\u0000{pi} modes in Floquet topological insulator. Here, utilized the flexibility of\u0000the circuit, we construct the Floquet circuit with frequency-synthetic\u0000dimension and find the topological-protected deeply-subharmonic oscillations\u0000with the period extensively exceeding the doubling-driven period. In the\u0000construction framework, the periodically-driven mechanism is attained by\u0000implementing the circuit-oscillator hierarchy with the stepping-variation\u0000resonances in frequency domain. The zero and {pi} modes that arise at the\u0000Floquet band in the circuit indicate the anomalous boundary-bulk\u0000correspondence. The coexistence of zero and {pi} modes, results in a\u0000subharmonic oscillation with the extremely-low frequency on the edge of the\u0000Floquet circuit. Furthermore, we explore the Floquet band with the enhanced\u0000periodically-driven strength tailored by the component flexibility of the\u0000circuit. Our method provides a flexible scheme to study Floquet topological\u0000phases, and open a new path for realizing the deeply subwavelength system.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141500867","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 free electrons, i.e. plane waves, with wavevector k, and occupancy constrained by the Pauli exclusion principle, are explained in all introductory texts about solids. A free-electron description works surprisingly well for many properties of "simple" metals. It is assumed that the interior of the metal is essentially infinite, and surfaces are presumed irrelevant. Over the past 30 years, experiments that visualize surfaces have revolutionized solid state physics, stimulating new theory and applications. Therefore, a basic question is, how can the free electron picture be applied to properties of solids where surfaces play a prominent role? Various versions of an extended free-electron theory are used, but not always explained pedagogically. This paper focusses on idealized metallic films. Three versions (an oversimplified one and two stages of improvement) of a free-electron description of metal films are given. These versions are illustrated in detail for the specific example of a slab of aluminum with six layers of atoms.
量子自由电子，即波长为 k 的平面波，其占位受保利排除原理的限制，在有关固体的所有介绍性文字中都有解释。对 "简单 "金属特性的自由电子描述效果出奇地好。我们假定金属的内部基本上是无限的，表面被认为是无关紧要的。过去 30 年来，表面可视化实验彻底改变了固态物理学，激发了新的理论和应用。因此，一个基本问题是，如何将自由电子图景应用于表面起着重要作用的固体性质？人们使用了各种版本的扩展自由电子理论，但并不总能从教学角度加以解释。本文重点讨论理想化的金属薄膜。本文给出了金属膜自由电子描述的三个版本（一个过于简化的版本和两个改进阶段）。本文以具有六层原子的铝板为例，详细说明了这些版本。
{"title":"Free Electron Theory for Thin Metal Films","authors":"Philip B. Allen","doi":"arxiv-2406.16197","DOIUrl":"https://doi.org/arxiv-2406.16197","url":null,"abstract":"Quantum free electrons, i.e. plane waves, with wavevector k, and occupancy\u0000constrained by the Pauli exclusion principle, are explained in all introductory\u0000texts about solids. A free-electron description works surprisingly well for\u0000many properties of \"simple\" metals. It is assumed that the interior of the\u0000metal is essentially infinite, and surfaces are presumed irrelevant. Over the\u0000past 30 years, experiments that visualize surfaces have revolutionized solid\u0000state physics, stimulating new theory and applications. Therefore, a basic\u0000question is, how can the free electron picture be applied to properties of\u0000solids where surfaces play a prominent role? Various versions of an extended\u0000free-electron theory are used, but not always explained pedagogically. This\u0000paper focusses on idealized metallic films. Three versions (an oversimplified\u0000one and two stages of improvement) of a free-electron description of metal\u0000films are given. These versions are illustrated in detail for the specific\u0000example of a slab of aluminum with six layers of atoms.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"214 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141528815","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}
Qi Yao, Xiaotian Yang, Askar A. Iliasov, Mikhail I. Katsnelson, Shengjun Yuan
Electronic states play a crucial role in many quantum systems of moire superlattices, quasicrystals, and fractals. As recently reported in textit{Sierpi'{n}ski} lattices [Phys. Rev. B 107, 115424 (2023)], the critical states are revealed by the energy level-correlation spectra, which are caused by the interplay between aperiodicity and determined self-similarity characters. In the case of the textit{Sierpi'{n}ski Carpet}, our results further demonstrate that there is some degree of spatial overlap between these electronic states. These states could be strongly affected by its `seed lattice' of the $generator$, and slightly modulated by the dilation pattern and the geometrical self-similarity level. These electronic states are multifractal by scaling the $q$-order inverse participation ratio or fractal dimension, which correlates with the subdiffusion behavior. In the $gene$ pattern, the averaged state-based multifractal dimension of second-order would increase as its textit{Hausdoff dimension} increases. Our findings could potentially contribute to understanding quantum transports and single-particle quantum dynamics in fractals.
电子态在摩尔超晶格、准晶体和分形等许多量子系统中扮演着至关重要的角色。正如最近在（textit{Sierpi/'{n}ski}晶格中报道的那样[Phys. Rev. B 107, 115424 (2023)]，临界状态是由能级相关谱揭示的，而能级相关谱是由非周期性和确定的自相似性特征之间的相互作用引起的。在textit{Sierpi/'{n}ski 地毯}的情况下，我们的结果进一步证明了这些电子态之间存在一定程度的空间重叠。这些电子态可能会受到发生器 "种子晶格 "的强烈影响，并受到扩张模式和几何自相似性水平的轻微调制。这些电子态通过q$阶反参与比或分形维度的缩放而具有多分形性，这与亚扩散行为相关。在$基因$模式中，基于状态的二阶平均多分形维度会随着其textit{Hausdoff维度}的增加而增加。我们的发现可能有助于理解分形中的量子传输和单粒子量子力学。
{"title":"Wave functions in the Critical Phase: a Planar textit{Sierpiński} Fractal Lattice","authors":"Qi Yao, Xiaotian Yang, Askar A. Iliasov, Mikhail I. Katsnelson, Shengjun Yuan","doi":"arxiv-2406.16130","DOIUrl":"https://doi.org/arxiv-2406.16130","url":null,"abstract":"Electronic states play a crucial role in many quantum systems of moire\u0000superlattices, quasicrystals, and fractals. As recently reported in\u0000textit{Sierpi'{n}ski} lattices [Phys. Rev. B 107, 115424 (2023)], the\u0000critical states are revealed by the energy level-correlation spectra, which are\u0000caused by the interplay between aperiodicity and determined self-similarity\u0000characters. In the case of the textit{Sierpi'{n}ski Carpet}, our results\u0000further demonstrate that there is some degree of spatial overlap between these\u0000electronic states. These states could be strongly affected by its `seed\u0000lattice' of the $generator$, and slightly modulated by the dilation pattern and\u0000the geometrical self-similarity level. These electronic states are multifractal\u0000by scaling the $q$-order inverse participation ratio or fractal dimension,\u0000which correlates with the subdiffusion behavior. In the $gene$ pattern, the\u0000averaged state-based multifractal dimension of second-order would increase as\u0000its textit{Hausdoff dimension} increases. Our findings could potentially\u0000contribute to understanding quantum transports and single-particle quantum\u0000dynamics in fractals.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"73 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141500871","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 Semiempirical Pseudopotential Method (SEPM) has emerged as a valuable tool for accurately determining band structures, especially in the realm of low-dimensional materials. SEPM operates by utilizing atomic pseudopotentials, which are derived from DFT calculations. SEPM calculations offer a unique advantage compared to DFT as they eliminate the requirement for iterative self-consistent solutions in solving the Schr"odinger equation, leading to a substantial reduction in computational complexity. The incorporation of both non-local and local Semiempirical Pseudopotentials in our current approach yields band structures and wavefunctions with enhanced precision compared to traditional empirical methods. When applied to monolayer TMDCs, adjusting the parameters to align with pertinent values obtained from DFT computations enables us to faithfully replicate the band structure, opening avenues for investigating the optoelectronic properties of TMDCs and exploring their potential applications in nanodevices.
{"title":"Efficient Band Structure Calculation for Transitional-Metal Dichalcogenides Using the Semiempirical Pseudopotential Method","authors":"Raj Kumar Paudel, Chung-Yuan Ren, Yia-Chung Chang","doi":"arxiv-2406.15913","DOIUrl":"https://doi.org/arxiv-2406.15913","url":null,"abstract":"The Semiempirical Pseudopotential Method (SEPM) has emerged as a valuable\u0000tool for accurately determining band structures, especially in the realm of\u0000low-dimensional materials. SEPM operates by utilizing atomic pseudopotentials,\u0000which are derived from DFT calculations. SEPM calculations offer a unique\u0000advantage compared to DFT as they eliminate the requirement for iterative\u0000self-consistent solutions in solving the Schr\"odinger equation, leading to a\u0000substantial reduction in computational complexity. The incorporation of both\u0000non-local and local Semiempirical Pseudopotentials in our current approach\u0000yields band structures and wavefunctions with enhanced precision compared to\u0000traditional empirical methods. When applied to monolayer TMDCs, adjusting the\u0000parameters to align with pertinent values obtained from DFT computations\u0000enables us to faithfully replicate the band structure, opening avenues for\u0000investigating the optoelectronic properties of TMDCs and exploring their\u0000potential applications in nanodevices.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"202 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141520112","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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