铋硫属化物Bi $_2$ Se $_3$和Bi $_2$ Te $_3$是半导体，其可以是热电材料（TE）和拓扑绝缘体（TI）。由这些材料中的空位、杂质或掺杂剂引起的晶格缺陷是重要的，因为它们在TE应用中提供了载流子并损害了这些材料作为TI的性能。我们提出了第一个固态核磁共振（NMR）研究的$^{77}$硒和$^{125}$碲核磁共振共振在多晶粉末的铋$_2$硒$_3$和铋$_2$碲$_3$，分别。自旋-晶格（$T_1$）弛豫由至多两个指数来建模。在这个模型的框架内，NMR测量是敏感的，这些材料内的原生缺陷的分布。一种成分对应于化学计量分数，绝缘体具有非常长的$T_1$，而另一种成分归因于具有高缺陷含量的样品分数，其具有由与传导载流子的相互作用产生的短$T_1$。碲化铋中不存在非常长的$T_1$表明整个样品中存在缺陷。对于硒化铋，缺陷区域分离成域。我们还发现一个实质性的差异，在短$T_1$组件$^{125}$ Te核（76毫秒）和$^{77}$硒（0.63秒），尽管这些材料具有几乎相同的晶格结构，化学和物理性质。的NMR位移和Korringa定律的调查表明，在硫属化物网站的导带电子的耦合是更强的碲化物。结果与碲化物中$p$带电子的较强自旋轨道耦合（SOC）一致。如果给定材料的大多数参数保持相等，这种类型的实验可以提供工程TI材料中SOC的有用探针。
英文摘要：
Bismuth chalcogenides Bi$_2$Se$_3$ and Bi$_2$Te$_3$ are semiconductors, which can be both thermoelectric materials (TE) and topological insulators (TI). Lattice defects arising from vacancies, impurities, or dopants in these materials are important in that they provide the charge carriers in TE applications and compromise the performance of these materials as TIs. We present the first solid-state nuclear magnetic resonance (NMR) study of the $^{77}$Se and $^{125}$Te NMR resonances in polycrystalline powders of Bi$_2$Se$_3$ and Bi$_2$Te$_3$, respectively. The spin-lattice ($T_1$) relaxation is modeled by at most two exponentials. Within the framework of this model, the NMR measurement is sensitive to the distribution of native defects within these materials. One component corresponds to a stoichiometric fraction, an insulator with a very long $T_1$, whereas the other component is attributed to a sample fraction with high defect content with a short $T_1$ resulting from interaction with the conduction carriers. The absence of a very long $T_1$ in the bismuth telluride suggests defects throughout the sample. For the bismuth selenide, defect regions segregate into domains. We also find a substantial difference in the short $T_1$ component for $^{125}$Te nuclei (76 ms) and $^{77}$Se (0.63 s) in spite of the fact that these materials have nearly identical lattice structures, chemical and physical properties. Investigations of the NMR shift and Korringa law indicate that the coupling to the conduction band electrons at the chalcogenide sites is much stronger in the telluride. The results are consistent with a stronger spin-orbit coupling (SOC) to the $p$-band electrons in the telluride. If most parameters of a given material are kept equal, this type of experiment could provide a useful probe of SOC in engineered TI materials.
Spectroscopic techniques, including photoelectron spectroscopy, diffuse reflectance, and x-ray absorption, are used to investigate the electronic structure and the local structure of LaOBiS$_{2-x}$Se$_x$ thermoelectric material. It is found that Se substitution effectively suppresses local distortion, that can be responsible for the increased carrier mobility together with a change in the electronic structure. The results suggest a possible way to control thermoelectric properties by tuning of the local crystal structure of these materials.
Dirac fermions at high-index surfaces of bismuth chalcogenide topological insulator nanostructures
二元铋硫属化物Bi $_2$ Se $_3$、Bi $_2$ Te $_3$和相关材料由于其简单的表面态带色散（单狄拉克锥）和相对大的体带隙而作为参考拓扑绝缘体（TI）目前被广泛研究。TI的纳米结构是特别感兴趣的，因为增加的表面体积比增强了表面状态的贡献，这意味着它们是潜在器件应用的有希望的候选者。到目前为止，绝大多数的研究工作都集中在低能量（0001）表面，这对应于这些层状材料中的自然解理面。然而，低维纳米结构（纳米片，纳米线，纳米带）的表面不可避免地涉及更高的折射率面。我们进行了系统的从头算研究铋硫属TI纳米结构的表面，其特征在于不同的晶体取向，原子结构和化学计量组成。我们发现几个稳定的终端的高指数表面，这可以实现在不同的值的化学势的组成元素之一。对于唯一定义的化学计量终止，拓扑狄拉克费米子状态被证明是强烈的各向异性与费米速度和自旋极化的表面取向上的一个明确的依赖。自掺杂效应和拓扑平凡的中间间隙状态的存在下被发现的非化学计量表面的特征。我们的研究结果铺平了道路，对实验控制的拓扑保护的表面状态铋硫族化物纳米结构。
Tetradymite-structured chalcogenides such as bismuth telluride Bi_{2}Te_{3} are of significant interest for thermoelectric energy conversion and as topological insulators. Dislocations play a critical role during synthesis and processing of such materials and can strongly affect their functional properties. The dislocations between quintuple layers present special interest since their core structure is controlled by the van der Waals interactions between the layers. In this work, using atomic-resolution electron microscopy, we resolve the basal dislocation core structure in Bi_{2}Te_{3}, quant…
Epitaxial films of bismuth telluride topological insulators have received increasing attention due to potential applications in spintronic and quantum computation. One of the most important properties of epitaxial films is the presence of interface defects due to lateral lattice mismatch since electrically active defects can drastically compromise device performance. By describing hybrid reflections in hexagonal bismuth telluride films on cubic substrates, in-plane lattice mismatches were characterized with accuracy at least 20 times better than using other X-ray diffraction methods, providing…
The high-throughput (HT) computational method is a useful tool to screen high performance functional materials. In this work, using the deformation potential method under the single band model, we evaluate the carrier relaxation time and establish an electrical descriptor (\c{hi}) characterized by the carrier effective masses based on the simple rigid band approximation. The descriptor (\c{hi}) can be used to reasonably represent the maximum power factor without solving the electron Boltzmann transport equation. Additionally, the Grüneisen parameter (γ), a descriptor of the lattice anharmonici…
Revealing the bonding and time-evolving atomic dynamics in functional materials with complex lattice structures can update the fundamental knowledge on rich physics therein, and also help to manipulate the material properties as desired. As the most prototypical chalcogenide phase change material, Ge2Sb2Te5 has been widely used in optical data storage and non-volatile electric memory due to the fast switching speed and the low energy consumption. However, the basic understanding of the structural dynamics on the atomic scale is still not clear. Using femtosecond electron diffraction, structure…
X-ray photo-induced atomic motion in Phase Change Materials and conventional covalent chalcogenide glasses
Institut Néel, Université Grenoble Alpes and Centre National de la Recherche Scientifique（尼斯研究所，格勒诺布尔阿尔卑斯大学及法国国家科学研究中心）；Department of Physics, University of Trento（特伦托大学物理系）；Department of Chemistry, Aarhus University（奥胡斯大学化学系）；European Synchrotron Radiation Facility（欧洲同步辐射装置）；Deutsches Elektronen-Synchrotron DESY（德国电子同步加速器）；ICGM, Université de Montpellier, CNRS, ENSCM（材料化学与全球分子实验室，蒙彼利埃大学，法国国家科学研究中心及国立化学学院）
Reversible and nonvolatile manipulation of the spin-orbit interaction in ferroelectric field-effect transistors based on a two-dimensional bismuth oxychalcogenide
Hierarchical Characterization of Thermoelectric Performance in Copper-Based Chalcogenide CsCu$_3$S$_2$: Unveiling the role of Anharmonic Lattice Dynamics
Large-scale defects hidden inside a topological insulator grown onto a 2D substrate
拓扑绝缘体（TI）材料是集成到下一代存储器和逻辑器件中的令人兴奋的候选材料，因为它们具有高效、低能耗的磁化切换的潜力。具体地，铋硫族化物家族提供有效的自旋-电荷转换，因为其大的自旋-轨道耦合和表面态的自旋-动量锁定。然而，实现TI的承诺的一个主要障碍是薄膜材料的质量，这落后于外延生长的半导体。与后一种系统相反，Bi硫族化物通过范德华外延形成，这使得它们能够成功地生长在具有不同程度晶格失配的衬底上。这种灵活性使得能够将TI集成到具有新兴材料（包括二维材料）的异质结构中。然而，了解和控制TI膜内的局部特征和缺陷对于实现突破性器件性能至关重要。在这里，我们报告的观测和建模的大规模的结构缺陷（Bi，Sb）$_2$ Te $_3$薄膜生长到六方氮化硼，突出了意想不到的破坏旋转的薄膜和沿晶界共存的第二相。使用第一性原理计算，我们表明，这些缺陷可能会对依赖于这些TI薄膜的器件产生相应的影响，因此它们不能被忽略。
Chalcogenide phase change materials enable non-volatile, low-latency storage-class memory. They are also being explored for new forms of computing such as neuromorphic and in-memory computing. A key challenge, however, is the temporal drift in the electrical resistance of the amorphous states that encode data. Drift, caused by the spontaneous structural relaxation of the newly recreated melt-quenched amorphous phase, has consistently been observed to have a logarithmic dependence in time. Here, we show that this observation is valid only in a certain observable timescale. Using threshold-switc…
The family of rare earth chalcogenides $ARECh_{2}$ (A = alkali or monovalent ions, RE = rare earth, and Ch = O, S, Se, and Te) appears as an inspiring playground for studying quantum spin liquids (QSL). The crucial low-energy spin dynamics remain to be uncovered. By employing muon spin relaxation ($μ$SR) and zero-field (ZF) AC susceptibility down to 50 mK, we are able to identify the gapless QSL in $NaYbSe_{2}$, a representative member with an effective spin-1/2, and explore its unusual spin dynamics. The ZF $μ$SR experiments unambiguously rule out spin ordering or freezing in $NaYbSe_{2}$ dow…
Understanding Bulk Defects in Topological Insulators from Nuclear-Spin Interactions
非侵入性的局部探针需要在二元和三元硫属化合物的体缺陷的特征。这些缺陷导致了拓扑绝缘体的非理想行为。用$^{125}$ Te核磁共振研究了Bi $_2$ Te $_3$，Sb $_2$ Te $_3$，Bi $_{0.5}$ Sb $_{1.5}$ Te $_3$，Bi $_2$ Te $_2$ Se和Bi $_2$ $_2$ Te $_2$ S.缺陷的分布引起粉末线形的不对称性。我们展示了如何骑士移位，线的形状和自旋晶格弛豫报告载流子密度，自旋轨道耦合和相分离的散装。本研究证实了有序三元化合物Bi $_2$ Te $_2$ Se是目前最好的TI候选材料。我们的研究结果，这是在良好的协议与运输和ARPES研究，帮助建立NMR探针作为一个有价值的方法来表征这些材料的本体属性。
Unusual double-peak specific heat and spin freezing in a spin-2 triangular lattice antiferromagnet FeAl$_{2}$Se$_{4}$
本文报道了三角晶格铁硫系反铁磁体FeAl $_{2}$ Se $_{4}$的性质。自旋磁化率显示出明显的反铁磁相互作用，居里-外斯温度Θ $_{CW}$ ~-200 K，自旋为2的局域磁矩。尽管有一个大的旋转和一个大的|Θ $_{CW}$|的低温行为与传统的经典磁体是不相容的。没有检测到低至0.4K的长程序。FeAl $_{2}$ Se $_{4}$的比热与NiGa $_{2}$ S $_{4}$相似，在低温下呈现出不寻常的双峰结构和T $^{2}$幂律，这分别归因于四极自旋关联和Halperin-Saslow模.自旋冻结发生在~ 14 K，低于该温度的弛豫动力学由交流磁化率探测。我们的结果与自旋为1的海森伯和双二次自旋相互作用系统的早期理论是一致的。我们认为，四极关联和规范玻璃动力学的早期建议可以很好地扩展到FeAl $_{2}$ Se $_{4}$。我们的结果提供了有用的见解与高自旋的受抑量子磁体的磁性。
