Intrinsic triferroicity is essential and highly sought for novel device applications, such as high-density multistate data storage. So far, the intrinsic triferroicity has only been discussed in three-dimensional systems. Herein on basis of first-principles, we report the intrinsic triferroicity in two-dimensional lattice. Being exfoliatable from the layered bulk, single-layer FeO2H is shown to be an intrinsically triferroic semiconductor, presenting antiferromagnetism, ferroelasticity and ferroelectricity simultaneously. Moreover, the directional control of its ferroelectric polarization is achievable by 90° reversible ferroelastic switching. In addition, single-layer FeO2H is identified to harbor in-plane piezoelectric effect. The unveiled phenomena and mechanism of triferroics in this two-dimensional system not only broaden the scientific and technological impact of triferroics but also enable a wide range of nanodevice applications.
Chiral magnetic insulators manifest novel phases of matter where the sense of rotation of the magnetization is associated with exotic transport phenomena. Effective control of such phases and their dynamical evolution points to the search and study of chiral fields like the Dzyaloshinskii-Moriya interaction. Here we combine experiments, numerics, and theory to study a zig-zag dipolar lattice as a model of an interface between magnetic in-plane layers with perpendicular magnetization. The zig-zag lattice comprises two parallel sublattices of dipoles with perpendicular easy plane of rotation. Th…
Faculty of Physics, Mathematics and Optometry（物理、数学与视光学院）；University of Latvia（拉脱维亚大学）
In this work we propose Support Vector Machine classification algorithms to classify onedimensional crystal lattice waves from locally sampled data. Different learning datasets of particle displacements, momenta and energy density values are considered. Efficiency of the classification algorithms is further improved by two dimensionality reduction techniques: Principal Component Analysis and Locally Linear Embedding. Robustness of classifiers is investigated and demonstrated. Developed algorithms are successfully applied to detect localized intrinsic modes in three numerical simulations consid…
Very recently, a novel two-dimension (2D) MXene, MoSi$_2$N$_4$, was successfully synthesized with excellent ambient stability, high carrier mobility, and moderate band gap (Science 369, 670, 2020). In this work, the intrinsic lattice thermal conductivity of monolayer MoSi$_2$N$_4$ is predicted by solving the phonon Boltzmann transport equation based on the first-principles calculations. Despite the heavy atomic mass of Mo and complex crystal structure, the monolayer MoSi$_2$N$_4$ unexpectedly exhibits a quite high lattice thermal conductivity over a wide temperature range between 300 to 800 K.…
Towards intrinsic phonon transport in single-layer MoS$_2$
MoS $_2$的本征晶格热导率是设计MoS $_2$基纳米电子器件的一个重要方面。我们利用第一性原理计算研究了MoS $_2$的晶格动力学性质。利用声子的玻尔兹曼输运方程计算了单层MoS $_2$的本征热导率。得到的热导率与测量值吻合良好。计算了声学声子和光学声子对晶格热导率的贡献。研究了热导率的尺寸依赖性。
Valley-related multiple Hall effect in 2D lattice is a fundamental transport phenomenon in the fields of condensed-matter physics and material science. So far, most proposals for its realization are limited to toy models or extrinsic effects. Here, based on tight-binding model and first-principles calculations, we report the discovery of intrinsic valley-related multiple Hall effect in 2D organometallic lattice of NbTa-benzene. Protected by the breaking of both time-reversal and inversion symmetry, NbTa-benzene exhibits large valley polarization spontaneously in both the conduction and valence…
Muffin-tin methods have been instrumental in the design of honeycomb lattices that show, in contrast to graphene, separated s and in-plane p bands, a p orbital Dirac cone, and a p orbital flat band. Recently, such lattices have been experimentally realized using the 2D electron gas on Cu(111). A possible next avenue is the introduction of spin-orbit coupling to these systems. Intrinsic spin-orbit coupling is believed to open topological gaps, and create a topological flat band. Although Rashba coupling is straightforwardly incorporated in the muffin-tin approximation, intrinsic spin-orbit coup…
Measurement of intrinsic Dirac fermion cooling on the surface of a topological insulator Bi$_2$Se$_3$ using time- and angle-resolved photoemission spectroscopy
我们进行时间和角度分辨的光电子能谱的原型拓扑绝缘体Bi $_2$ Se $_3$的表面和体电子光激发后的超快动力学研究。通过分析表面态和体能带谱的演化，分别得到了它们的电子温度和化学势弛豫动力学。这些动力学揭示了强声子辅助的表面-体耦合在高晶格温度和总抑制在低晶格温度的表面和体之间的非弹性散射。在这个低温制度下，独特的冷却狄拉克费米子在TI的声学声子表现出通过幂律依赖的表面温度衰减速率载流子密度。
We report magnetic and electrical properties for single crystals of NdMn$_6$Sn$_6$ and SmMn$_6$Sn$_6$. They crystallize into a structure which has distorted, Mn-based kagome lattices, compared to the pristine kagome lattices in heavy-rare-earth-bearing RMn$_6$Sn$_6$ compounds. They are hightemperature ferromagnets of which the R moment is parallel with the Mn moment. We observed a large intrinsic anomalous Hall effect (AHE) that is comparable to the ferrimagnetic, heavy-R siblings in a wide range of temperature. We conclude that their intrinsic AHE is stemming from the Mn-based kagome lattice,…
