Spin-wave Confinement and Coupling in Organic-Based Magnetic Nanostructures
Michael Chilcote, Megan Harberts, Bodo Fuhrman, Katrin Lehmann, Yu Lu, Andrew Franson, Howard Yu, Na Zhu, Hong Tang, Georg Schmidt, Ezekiel Johnston-Halperin
Vanadium tetracyanoethylene (V[TCNE]$_\text{x}$) is an organic-based ferrimagnet that exhibits robust magnetic ordering (T$_\text{C}$ of over 600 K), high quality-factor (high-Q) microwave resonance (Q up to 3,500), and compatibility with a wide variety of substrates and encapsulation technologies. Here, we substantially expand the potential scope and impact of this emerging material by demonstrating the ability to produce engineered nanostructures with tailored magnetic anisotropy that serve as a platform for the exploration of cavity magnonics, revealing strongly coupled quantum confined standing wave modes that can be tuned into and out of resonance with an applied magnetic field. Specifically, time-domain micromagnetic simulations of these nanostructures faithfully reproduce the experimentally measured spectra, including the quasi-uniform mode and higher-order spin-wave (magnon) modes. Finally, when the two dominant magnon modes present in the spectra are brought into resonance by varying the orientation of the in-plane magnetic field, we observe anti-crossing behavior indicating strong coherent coupling between these two magnon modes at room temperature. These results position V[TCNE]$_\text{x}$ as a leading candidate for the development of coherent magnonics, with potential applications ranging from microwave electronics to quantum information.
An Environment-dependent Semi-Empirical Tight Binding Model Suitable for Electron Transport in Bulk Metals, Metal Alloys, Metallic Interfaces and Metallic Nanostructures II - Effect of Confinement and Homogeneous Strain on Cu Conductance
Overhauser frequency shifts in semiconductor nanostructures
我们计算了半导体纳米结构中由于非平衡电子自旋和核自旋之间的超精细相互作用而产生的Overhauser频率偏移。频移取决于电子局域态密度和自旋极化以及电子和核自旋弛豫机制。与以前的计算不同，我们的方法考虑了低维半导体纳米结构中的电子约束，导致核自旋极化和Overhauser位移强烈依赖于位置。我们的研究结果解释了以前令人困惑的测量Overhauser位移在Al $_x$ Ga $_{1-x}$ As抛物量子阱显示电子自旋寿命和频率偏移之间的连接。
Electronic properties of one-dimensional nanostructures of the Bi$_2$Se$_3$ topological insulator
我们从理论上研究了典型的块体拓扑绝缘体Bi $_2$ Se $_3$的一维纳米结构的电子结构和自旋性质。实验观察到的Bi $_2$ Se $_3$纳米线和纳米带的现实模型被认为是使用紧束缚方法。在低能量下，能带结构由一系列均匀间隔的简并子带组成，这些子带是由拓扑表面态的周向限制引起的。由于非平凡的$π$ Berry相位的直接带隙显示出明显的依赖于周长。拓扑表面状态的自旋-动量锁定导致围绕圆周的显著的2 $π$自旋旋转，其中自旋极化的程度取决于沿着纳米结构的动量。总的来说，纳米带的能带结构和自旋织构更复杂，暴露出两个不同的小面。降维的影响合理化的帮助下，一个简单的模型，认为圆周量子化的拓扑表面状态。此外，由电流沿纳米结构诱导的表面自旋密度显示出对电荷载流子能量的明显振荡依赖性，这可以在自旋电子学应用中被利用。
3D Electron Diffraction -- The Missing Slice for a Complete Nanoscale Analysis of Organic Solar Cells in TEM
Friedrich-Alexander-Universität Erlangen-Nürnberg（埃尔朗根-纽伦堡大学）；Institute of Micro- and Nanostructure Research & Center for Nanoanalysis and Electron Microscopy (CENEM)（微纳结构研究所与纳米分析与电子显微镜中心）；Institute for Crystallography and Structural Physics（晶体学与结构物理研究所）；Institute for a Sustainable Hydrogen Economy (INW), Forschungszentrum Jülich GmbH（于利希研究中心可持续氢能研究所）；RWTH Aachen University（亚琛工业大学）；Paderborn University（帕德博恩大学）；Institute Materials for Electronics and Energy Technology (iMEET)（电子与能源技术材料研究所）；Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (HIERN)（埃尔朗根-纽伦堡亥姆霍兹可再生能源研究所）；Deutsches Elektronen-Synchrotron DESY（德国电子同步辐射中心）
Two-dimensional hole gas in organic semiconductors
量子力学限制在固态界面的高导电金属气体是探索非平凡电子态的理想平台，否则在大块材料中无法获得。虽然二维电子气（2DEG）已经在常规半导体界面中实现，但是作为2DEG的相反类似物的二维空穴气（2DHG）的实例仍然有限。在这里，我们报告的2DHG在溶液处理的有机半导体结合使用离子液体的双电层的观察。高迁移率有机半导体的分子平坦单晶用作无缺陷界面，其促进高密度空穴的二维限制。6 k $Ω$的显著低的薄层电阻和10 $^{14}$ cm $^{-2}$的高空穴气体密度导致在环境压力下的金属-绝缘体转变。在有机半导体中测量的简并空穴提供了一个广泛的机会，使用分子工程异质界面定制低维电子态。
