Spin and valley are two fundamental properties of electrons in crystals. The similarity between them is well understood in valley-contrasting physics established decades ago in two-dimensional (2D) materials like graphene--with broken inversion symmetry, the two valleys in graphene exhibit opposite orbital magnetic moments, similar to the spin-1/2 behaviors of electrons, and opposite Berry curvature that leads to a half topological charge. However, valley-contrasting physics has never been explored in 3D crystals. Here, we develop a 3D acoustic crystal exhibiting 3D valley-contrasting physics. Unlike spin that is fundamentally binary, valley in 3D can take six different values, each carrying a vortex in a distinct direction. The topological valley transport is generalized from the edge states of 2D materials to the surface states of 3D materials, with interesting features including robust propagation, topological refraction, and valley-cavity localization. Our results open a new route for wave manipulation in 3D space.
{"title":"Three-dimensional valley-contrasting sound","authors":"Haoran Xue, Yong Ge, Zheyu Cheng, Yi-jun Guan, Jiaojiao Zhu, Hong-yu Zou, Shou-qi Yuan, Shengyuan A. Yang, Hong-xiang Sun, Yidong Chong, Baile Zhang","doi":"arxiv-2409.11714","DOIUrl":"https://doi.org/arxiv-2409.11714","url":null,"abstract":"Spin and valley are two fundamental properties of electrons in crystals. The\u0000similarity between them is well understood in valley-contrasting physics\u0000established decades ago in two-dimensional (2D) materials like graphene--with\u0000broken inversion symmetry, the two valleys in graphene exhibit opposite orbital\u0000magnetic moments, similar to the spin-1/2 behaviors of electrons, and opposite\u0000Berry curvature that leads to a half topological charge. However,\u0000valley-contrasting physics has never been explored in 3D crystals. Here, we\u0000develop a 3D acoustic crystal exhibiting 3D valley-contrasting physics. Unlike\u0000spin that is fundamentally binary, valley in 3D can take six different values,\u0000each carrying a vortex in a distinct direction. The topological valley\u0000transport is generalized from the edge states of 2D materials to the surface\u0000states of 3D materials, with interesting features including robust propagation,\u0000topological refraction, and valley-cavity localization. Our results open a new\u0000route for wave manipulation in 3D space.","PeriodicalId":501137,"journal":{"name":"arXiv - PHYS - Mesoscale and Nanoscale Physics","volume":"39 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142253496","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}
Stefania De Palo, Saverio Moroni, Francesco Ancilotto, Pierluigi Silvestrelli, Luciano Reatto
In search of substrates for adsorption of He atoms allowing for novel quantum phases in restricted geometry we study the case of borophane. We focus on two allotropes of borophane, alpha-4H and Rect-2H. With a suitable Density Functional Theory we characterize the adsorption potential of a He atom on such crystalline substrates finding its corrugation, the preferential adsorption sites and the energy barrier between sites. Rect-2H borophane is particularly interesting due to thepresence of ridges in the adsorption potential with modest energy barriers in one direction of the basal plane and much higher barrier in the orthogonal direction, thus forming channels for motion of the adsorbed atoms. We study the adsorption of He-4 on Rect-2H borophane using Path Integral Monte Carlo simulations. In the first adsorbed layer the He-4 atoms are rather delocalized along a channel with no exchanges between channels. This strong anisotropy is present also in the first few additional adsorption layers of He-4 with presence of ordered and of disordered regions. In the second and the fifth layers at low temperature we find superfluidity on the length scale of the simulated systems. In the second layer the superfluidity is one-dimensional along the grooves. In the fifth layer the state is a strongly anisotropic two-dimensional superfluid at low coverage, with a crossover to an isotropic one at layer completion. Starting from the sixth layer the adsorbed He-4 film evolves toward a three-dimensional superfluid. Our main prediction is that Rect-2H borophane as a substrate will allow to probe 1D superfluidity in the second absorption layer, as well as the evolution from a 2D anisotropic superfluid to an isotropic one in the fifth layer, and eventually the onset of 3D superfluidity for higher coverages.
为了寻找吸附 He 原子的基质，以便在受限几何形状中实现新的量子相，我们对硼烷进行了研究。我们重点研究了硼烷的两种异构体：α-4H 和 Rect-2H。通过合适的密度函数理论，我们描述了 He 原子在这种晶体基底上的吸附势，发现了其波纹、优先吸附位点和位点间的能量势垒。矩形-2H硼烷尤其令人感兴趣，因为它的吸附势中存在脊，在基面的一个方向上能量势垒最低，而在正交方向上的能量势垒则高得多，从而形成了吸附原子的运动通道。我们使用 PathIntegral 蒙特卡洛模拟研究了 He-4 在 Rect-2H 硼烷上的吸附。在第一吸附层中，He-4 原子沿着通道分散，通道之间没有交换。这种强烈的各向异性也存在于 He-4 的最初几个附加吸附层中，其中存在有序区和无序区。在低温下的第二层和第五层，我们发现了模拟系统长度尺度上的超流动性。在第二层，沿沟槽的超流动是一维的。在第五层，在低覆盖率时，超流状态是强各向异性的二维超流，在层完成时过渡到各向异性的超流。从第六层开始，吸附的 He-4 薄膜向三维超流体演化。我们的主要预测是，以 2H 直硼烷为基底可以探测第二吸附层的一维超流体，以及第五层从二维各向异性超流体向各向同性超流体的演化，并最终在较高的覆盖率下出现三维超流体。
{"title":"Borophane as substrate for adsorption of He-4: A journey across dimensionality","authors":"Stefania De Palo, Saverio Moroni, Francesco Ancilotto, Pierluigi Silvestrelli, Luciano Reatto","doi":"arxiv-2409.11913","DOIUrl":"https://doi.org/arxiv-2409.11913","url":null,"abstract":"In search of substrates for adsorption of He atoms allowing for novel quantum\u0000phases in restricted geometry we study the case of borophane. We focus on two\u0000allotropes of borophane, alpha-4H and Rect-2H. With a suitable Density\u0000Functional Theory we characterize the adsorption potential of a He atom on such\u0000crystalline substrates finding its corrugation, the preferential adsorption\u0000sites and the energy barrier between sites. Rect-2H borophane is particularly\u0000interesting due to thepresence of ridges in the adsorption potential with\u0000modest energy barriers in one direction of the basal plane and much higher\u0000barrier in the orthogonal direction, thus forming channels for motion of the\u0000adsorbed atoms. We study the adsorption of He-4 on Rect-2H borophane using Path\u0000Integral Monte Carlo simulations. In the first adsorbed layer the He-4 atoms\u0000are rather delocalized along a channel with no exchanges between channels. This\u0000strong anisotropy is present also in the first few additional adsorption layers\u0000of He-4 with presence of ordered and of disordered regions. In the second and\u0000the fifth layers at low temperature we find superfluidity on the length scale\u0000of the simulated systems. In the second layer the superfluidity is\u0000one-dimensional along the grooves. In the fifth layer the state is a strongly\u0000anisotropic two-dimensional superfluid at low coverage, with a crossover to an\u0000isotropic one at layer completion. Starting from the sixth layer the adsorbed\u0000He-4 film evolves toward a three-dimensional superfluid. Our main prediction is\u0000that Rect-2H borophane as a substrate will allow to probe 1D superfluidity in\u0000the second absorption layer, as well as the evolution from a 2D anisotropic\u0000superfluid to an isotropic one in the fifth layer, and eventually the onset of\u00003D superfluidity for higher coverages.","PeriodicalId":501137,"journal":{"name":"arXiv - PHYS - Mesoscale and Nanoscale Physics","volume":"98 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142253494","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}
Dislocations in van der Waals materials are linear defects confined to the interfaces between consecutive stoichiometric monolayers of a bulk layered crystal. Here, we present a mesoscale model for the description of interlayer dislocations in thin films of transition metal dichalcogenides. Taking 2H-MoS${}_2$ as a representative material, we compute the dependence of the dislocation energy on the film thickness, from few-layer MoS$_2$ to the bulk crystal, and analyse the strain field in the layers surrounding a dislocation. We also analyse the influence of strain field on the band edge profiles for electrons and holes, and conclude that the resulting energy profiles are incapable of localising charge carriers, in particular at room temperature.
{"title":"Interlayer dislocations in multilayer and bulk MoS${}_2$","authors":"Isaac Soltero, Vladimir I. Fal'ko","doi":"arxiv-2409.12030","DOIUrl":"https://doi.org/arxiv-2409.12030","url":null,"abstract":"Dislocations in van der Waals materials are linear defects confined to the\u0000interfaces between consecutive stoichiometric monolayers of a bulk layered\u0000crystal. Here, we present a mesoscale model for the description of interlayer\u0000dislocations in thin films of transition metal dichalcogenides. Taking\u00002H-MoS${}_2$ as a representative material, we compute the dependence of the\u0000dislocation energy on the film thickness, from few-layer MoS$_2$ to the bulk\u0000crystal, and analyse the strain field in the layers surrounding a dislocation.\u0000We also analyse the influence of strain field on the band edge profiles for\u0000electrons and holes, and conclude that the resulting energy profiles are\u0000incapable of localising charge carriers, in particular at room temperature.","PeriodicalId":501137,"journal":{"name":"arXiv - PHYS - Mesoscale and Nanoscale Physics","volume":"100 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142253551","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}
Longju Yu, Hong Jian Zhao, Yurong Yang, Laurent Bellaiche, Yanming Ma
The anomalous Hall effect (AHE) is a topology-related transport phenomenon being of potential interest in spintronics, because this effect enables the efficient probe of magnetic orders (i.e., data readout in memory devices). It is well known that AHE spontaneously occurs in ferromagnets or antiferromagnets with magnetization. While recent studies reveal electric-field induced AHE (via linear magnetoelectric coupling), an AHE originating from nonlinear magnetoelectric coupling remains largely unexplored. Here, by symmetry analysis, we establish the phenomenological theory regarding the spontaneous and electric-field driven AHE in magnets. We show that a large variety of magnetic point groups host an AHE that is driven by uni-axial, bi-axial, or tri-axial electric field and that comes from nonlinear magnetoelectric coupling. Such electric-field driven anomalous Hall conductivities are reversible by reversing the magnetic orders. Furthermore, our first-principles calculations suggest Cr2O3 and CoF2 as candidates hosting the aforementioned AHE. Our work emphasizes the important role of nonlinear magnetoelectric coupling in creating exotic transport phenomena, and offers alternative avenues for the probe of magnetic orders.
{"title":"Anomalous Hall effect from nonlinear magnetoelectric coupling","authors":"Longju Yu, Hong Jian Zhao, Yurong Yang, Laurent Bellaiche, Yanming Ma","doi":"arxiv-2409.11662","DOIUrl":"https://doi.org/arxiv-2409.11662","url":null,"abstract":"The anomalous Hall effect (AHE) is a topology-related transport phenomenon\u0000being of potential interest in spintronics, because this effect enables the\u0000efficient probe of magnetic orders (i.e., data readout in memory devices). It\u0000is well known that AHE spontaneously occurs in ferromagnets or antiferromagnets\u0000with magnetization. While recent studies reveal electric-field induced AHE (via\u0000linear magnetoelectric coupling), an AHE originating from nonlinear\u0000magnetoelectric coupling remains largely unexplored. Here, by symmetry\u0000analysis, we establish the phenomenological theory regarding the spontaneous\u0000and electric-field driven AHE in magnets. We show that a large variety of\u0000magnetic point groups host an AHE that is driven by uni-axial, bi-axial, or\u0000tri-axial electric field and that comes from nonlinear magnetoelectric\u0000coupling. Such electric-field driven anomalous Hall conductivities are\u0000reversible by reversing the magnetic orders. Furthermore, our first-principles\u0000calculations suggest Cr2O3 and CoF2 as candidates hosting the aforementioned\u0000AHE. Our work emphasizes the important role of nonlinear magnetoelectric\u0000coupling in creating exotic transport phenomena, and offers alternative avenues\u0000for the probe of magnetic orders.","PeriodicalId":501137,"journal":{"name":"arXiv - PHYS - Mesoscale and Nanoscale Physics","volume":"44 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142253547","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}
Marcelo Lopes Pereira, Jr, Emanuel J. A. dos Santos, Luiz Antonio Ribeiro, Jr, Douglas Soares Galvão
The recent synthesis of Goldene, a 2D atomic monolayer of gold, has opened new avenues in exploring novel materials. However, the question of when multilayer Goldene transitions into bulk gold remains unresolved. This study used density functional theory calculations to address this fundamental question. Our findings reveal that multilayer Goldene retains an AA-like stacking configuration of up to six layers, with no observation of Bernal-like stacking as seen in graphene. Goldene spontaneously transitions to a bulk-like gold structure at seven layers, adopting a rhombohedral (ABC-like) stacking characteristic of bulk face-centered cubic (FCC) gold. The atomic arrangement converges entirely to the bulk gold lattice for more than ten layers. Quantum confinement significantly impacts the electronic properties, with monolayer and bulk Goldene exhibiting a single Dirac cone at the X-point of the Brillouin zone. In contrast, multilayer Goldene shows two Dirac cones at the X- and Y-points. Additionally, monolayer Goldene exhibits anisotropic optical absorption, which is absent in bulk gold. This study provides a deeper understanding of multilayer Goldene's structural and electronic properties and stacked 2D materials in general.
最近合成的二维原子单层金（Goldene）为探索新型材料开辟了新途径。然而，多层金何时转变为块状金的问题仍然悬而未决。本研究利用密度泛函理论计算来解决这一基本问题。我们的研究结果表明，多层金烯保留了多达六层的 AA-层叠构型，没有观察到石墨烯中出现的伯纳尔-层叠现象。金烯在七层时自发过渡到类体金结构，采用了类体面心立方（FCC）金的斜方体（ABC）堆积特征。在超过十层时，原子排列完全趋同于体金晶格。量子一致性对电子特性有很大影响，单层和块状金烯在布里渊区的 X 点表现出单一的狄拉克锥。相比之下，多层金烯在 X 点和 Y 点显示出两个狄拉克锥。此外，单层金烯还表现出各向异性的光吸收，这在块状金中是不存在的。这项研究加深了人们对多层金烯的结构和电子特性以及一般堆叠二维材料的理解。
{"title":"How does Goldene Stack?","authors":"Marcelo Lopes Pereira, Jr, Emanuel J. A. dos Santos, Luiz Antonio Ribeiro, Jr, Douglas Soares Galvão","doi":"arxiv-2409.11880","DOIUrl":"https://doi.org/arxiv-2409.11880","url":null,"abstract":"The recent synthesis of Goldene, a 2D atomic monolayer of gold, has opened\u0000new avenues in exploring novel materials. However, the question of when\u0000multilayer Goldene transitions into bulk gold remains unresolved. This study\u0000used density functional theory calculations to address this fundamental\u0000question. Our findings reveal that multilayer Goldene retains an AA-like\u0000stacking configuration of up to six layers, with no observation of Bernal-like\u0000stacking as seen in graphene. Goldene spontaneously transitions to a bulk-like\u0000gold structure at seven layers, adopting a rhombohedral (ABC-like) stacking\u0000characteristic of bulk face-centered cubic (FCC) gold. The atomic arrangement\u0000converges entirely to the bulk gold lattice for more than ten layers. Quantum\u0000confinement significantly impacts the electronic properties, with monolayer and\u0000bulk Goldene exhibiting a single Dirac cone at the X-point of the Brillouin\u0000zone. In contrast, multilayer Goldene shows two Dirac cones at the X- and\u0000Y-points. Additionally, monolayer Goldene exhibits anisotropic optical\u0000absorption, which is absent in bulk gold. This study provides a deeper\u0000understanding of multilayer Goldene's structural and electronic properties and\u0000stacked 2D materials in general.","PeriodicalId":501137,"journal":{"name":"arXiv - PHYS - Mesoscale and Nanoscale Physics","volume":"30 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142253500","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}
Sayan Sarkar, Sunit Das, Debottam Mandal, Amit Agarwal
The optical generation of nonequilibrium spin magnetization plays a crucial role in advancing spintronics, providing ultrafast control of magnetization dynamics without the need for magnetic fields. Here, we demonstrate the feasibility of light-induced nonlinear spin magnetization (LNSM), which becomes a dominant effect in centrosymmetric materials. We reveal the quantum geometric origins of various LNSM contributions in both metallic and insulating systems. Through detailed symmetry analysis, we predict significant LNSM in the antiferromagnetic material CuMnAs. Notably, under circularly polarized light, the spin magnetization exhibits helicity-dependent behavior, reversing with opposite light helicity. These findings open up new possibilities for generating LNSM-driven nonlinear spin-orbit torques and developing innovative opto-spintronic devices.
{"title":"Light-induced Nonlinear Resonant Spin Magnetization","authors":"Sayan Sarkar, Sunit Das, Debottam Mandal, Amit Agarwal","doi":"arxiv-2409.12142","DOIUrl":"https://doi.org/arxiv-2409.12142","url":null,"abstract":"The optical generation of nonequilibrium spin magnetization plays a crucial\u0000role in advancing spintronics, providing ultrafast control of magnetization\u0000dynamics without the need for magnetic fields. Here, we demonstrate the\u0000feasibility of light-induced nonlinear spin magnetization (LNSM), which becomes\u0000a dominant effect in centrosymmetric materials. We reveal the quantum geometric\u0000origins of various LNSM contributions in both metallic and insulating systems.\u0000Through detailed symmetry analysis, we predict significant LNSM in the\u0000antiferromagnetic material CuMnAs. Notably, under circularly polarized light,\u0000the spin magnetization exhibits helicity-dependent behavior, reversing with\u0000opposite light helicity. These findings open up new possibilities for\u0000generating LNSM-driven nonlinear spin-orbit torques and developing innovative\u0000opto-spintronic devices.","PeriodicalId":501137,"journal":{"name":"arXiv - PHYS - Mesoscale and Nanoscale Physics","volume":"21 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142253493","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}
Christian Marty, Zijin Lei, Saverio Silletta, Christian Reichl, Werner Dietsche, Werner Wegscheider
Resonant tunneling between closely spaced two dimensional electron gases is a single particle phenomenon that has sparked interest for decades. High tunneling conductances at equal electron densities are observed whenever the Fermi levels of the two quantum wells align. Detuning the Fermi levels out of the resonant 2D-2D tunneling regime causes a negative differential resistance. The negative differential resistance leads to a hysteresis when operating the device in a current driven mode, allowing a bilayer system to function as a volatile memory resistor.
{"title":"Memory resistor based in GaAs 2D-bilayers: In and out of equilibrium","authors":"Christian Marty, Zijin Lei, Saverio Silletta, Christian Reichl, Werner Dietsche, Werner Wegscheider","doi":"arxiv-2409.11850","DOIUrl":"https://doi.org/arxiv-2409.11850","url":null,"abstract":"Resonant tunneling between closely spaced two dimensional electron gases is a\u0000single particle phenomenon that has sparked interest for decades. High\u0000tunneling conductances at equal electron densities are observed whenever the\u0000Fermi levels of the two quantum wells align. Detuning the Fermi levels out of\u0000the resonant 2D-2D tunneling regime causes a negative differential resistance.\u0000The negative differential resistance leads to a hysteresis when operating the\u0000device in a current driven mode, allowing a bilayer system to function as a\u0000volatile memory resistor.","PeriodicalId":501137,"journal":{"name":"arXiv - PHYS - Mesoscale and Nanoscale Physics","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142253495","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 texture in antiferromagnets hosting a topologically protected skyrmion can be viewed as two effectively coupled ferromagnetic skyrmions. Assuming rigid magnetic configurations, we show that this coupling results in an effective mass of the antiferromagnetic skyrmion and that its dynamics can be viewed as due to a relative displacement of the two sublattice ferromagnetic skyrmions. The theory holds for different antiferromagnetic systems and includes effects from dissipation and external forces caused by electric currents. We verify our analytical results by micromagnetic simulations.
{"title":"Moving skyrmions in Antiferromagnets by Sublattice Displacements","authors":"Michael Lau, Wolfgang Häusler, Michael Thorwart","doi":"arxiv-2409.11493","DOIUrl":"https://doi.org/arxiv-2409.11493","url":null,"abstract":"The texture in antiferromagnets hosting a topologically protected skyrmion\u0000can be viewed as two effectively coupled ferromagnetic skyrmions. Assuming\u0000rigid magnetic configurations, we show that this coupling results in an\u0000effective mass of the antiferromagnetic skyrmion and that its dynamics can be\u0000viewed as due to a relative displacement of the two sublattice ferromagnetic\u0000skyrmions. The theory holds for different antiferromagnetic systems and\u0000includes effects from dissipation and external forces caused by electric\u0000currents. We verify our analytical results by micromagnetic simulations.","PeriodicalId":501137,"journal":{"name":"arXiv - PHYS - Mesoscale and Nanoscale Physics","volume":"86 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142253499","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 phonon thermal conductance of sub-nanometric vacuum gaps between two in-plane nanoribbons of two-dimensional materials (graphene and silicene) is analyzed using the atomistic Green's function method and by employing the Tersoff and Lennard-Jones potentials for describing the interatomic interactions. It is found that the phonon conductance decays exponentially with the size of the gap. Three exponential regimes have been identified. In the regime where the Lennard-Jones (L-J) potential is driven by the repulsive interatomic forces, caused by the overlap of electronic orbits, there is a sharp exponential decay in conductance as the gap increases (exp(-10.0d) for graphene). When both the repulsive and attractive (van der Waals) interatomic forces contribute to the L-J potential, the decay rate of the conductance significantly reduces to exp(-2.0d) for graphene and exp(-2.5d) for silicene. In the regime where attractive van der Waals forces dominate the L-J potential, phonon conductance has the slowest exponential decay as exp(-1.3d) for both silicene and graphene. It is also found that the contribution from the optical phonons to the conductance is non-negligible only for very small gaps between graphene nanoribbons (d < 1.6 AA). The phonon conductance of the gap is shown to vary with the width of the nanoribbon very modestly, such that the thermal conductivity of the gap linearly increases with the nanoribbon widths. The results of this study are of significance for fundamental understanding of heat transfer in the extreme near-field regime and for predicting the effect of interfaces and defects on heat transfer.
{"title":"Phonon Thermal Transport between Two in-Plane, Two-Dimensional Nanoribbons in the Extreme Near-Field Regime","authors":"Md Jahid Hasan Sagor, Sheila Edalatpour","doi":"arxiv-2409.11345","DOIUrl":"https://doi.org/arxiv-2409.11345","url":null,"abstract":"The phonon thermal conductance of sub-nanometric vacuum gaps between two\u0000in-plane nanoribbons of two-dimensional materials (graphene and silicene) is\u0000analyzed using the atomistic Green's function method and by employing the\u0000Tersoff and Lennard-Jones potentials for describing the interatomic\u0000interactions. It is found that the phonon conductance decays exponentially with\u0000the size of the gap. Three exponential regimes have been identified. In the\u0000regime where the Lennard-Jones (L-J) potential is driven by the repulsive\u0000interatomic forces, caused by the overlap of electronic orbits, there is a\u0000sharp exponential decay in conductance as the gap increases (exp(-10.0d) for\u0000graphene). When both the repulsive and attractive (van der Waals) interatomic\u0000forces contribute to the L-J potential, the decay rate of the conductance\u0000significantly reduces to exp(-2.0d) for graphene and exp(-2.5d) for silicene.\u0000In the regime where attractive van der Waals forces dominate the L-J potential,\u0000phonon conductance has the slowest exponential decay as exp(-1.3d) for both\u0000silicene and graphene. It is also found that the contribution from the optical\u0000phonons to the conductance is non-negligible only for very small gaps between\u0000graphene nanoribbons (d < 1.6 AA). The phonon conductance of the gap is shown\u0000to vary with the width of the nanoribbon very modestly, such that the thermal\u0000conductivity of the gap linearly increases with the nanoribbon widths. The\u0000results of this study are of significance for fundamental understanding of heat\u0000transfer in the extreme near-field regime and for predicting the effect of\u0000interfaces and defects on heat transfer.","PeriodicalId":501137,"journal":{"name":"arXiv - PHYS - Mesoscale and Nanoscale Physics","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142253548","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}
Carsten Speckmann, Andrea Angeletti, Lukáš Kývala, David Lamprecht, Felix Herterich, Clemens Mangler, Lado Filipovic, Christoph Dellago, Cesare Franchini, Jani Kotakoski
Phosphorene, a puckered two-dimensional allotrope of phosphorus, has sparked considerable interest in recent years due to its potential especially for optoelectronic applications with its layer-number-dependant direct band gap and strongly bound excitons. However, detailed experimental characterization of its intrinsic defects as well as its defect creation characteristics under electron irradiation are scarce. Here, we report on the creation and stability of a variety of defect configurations under 60 kV electron irradiation in mono- and bilayer phosphorene including the first experimental reports of stable adatom-vacancy-complexes. Displacement cross section measurements in bilayer phosphorene yield a value of 7.7 +- 1.4 barn with an estimated lifetime of adatom-vacancy-complexes of 19.9 +- 0.7 s, while some are stable for up to 68 s under continuous electron irradiation. Surprisingly, ab initio-based simulations indicate that the complexes should readily recombine, even in structures strained by up to 3 %. The presented results will help to improve the understanding of the wide variety of defects in phosphorene, their creation, and their stability, which may enable new pathways for defect engineered phosphorene devices.
磷烯是一种皱褶状的二维磷同素异形体，由于其具有与层数相关的直接带隙和强结合激子，特别是在光电子应用方面的潜力，近年来引发了人们的极大兴趣。然而，有关其内在缺陷及其在电子辐照下的缺陷产生特性的详细实验表征却很少见。在此，我们报告了单层和双层磷烯在 60 kV 电子辐照下各种缺陷构型的产生和稳定性，包括首次实验报告的稳定的原子-空位-复合物。双层磷化烯的位移截面测量值为 7.7 +- 1.4 barn，估计原子-空位复合物的寿命为 19.9 +- 0.7 s，而有些复合物在连续电子辐照下的稳定性可达 68 s。令人惊讶的是，基于 ab initio 的模拟表明，即使在应变高达 3% 的情况下，这些复合物也很容易发生重组。这些结果将有助于人们更好地了解磷化烯中的各种缺陷、它们的产生及其稳定性，从而为缺陷工程磷化烯器件开辟新的途径。
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