The long spin-diffusion length, spin-lifetimes and excellent optical absorption coefficient of graphene provide an excellent platform for building opto-electronic devices as well as spin-based logic in a nanometer regime. In this study, by employing density functional theory and its time-dependent version, we provide a detailed analysis of how the size and shape of graphene nanoflakes can be used to alter their magnetic structure and optical properties. As the edges of zigzag graphene nanoribbons are known to align anti-ferromagnetically and armchair nanoribbons are typically non-magnetic, a combination of both in a nanoflake geometry can be used to optimize the ground-state magnetic structure and tailor the exchange coupling decisive for ferro- or anti-ferromagnetic edge magnetism, thereby offering the possibility to optimize the external fields needed to switch magnetic ordering. Most importantly, we show that the magnetic state alters the optical response of the flake leading to the possibility of opto-spintronic applications.
Halide perovskite materials raised tremendous interest in recent years since their cheap fabrication, superior performance in both solar cell and light emitting diode (LED). Due to the existence of layered quantum well structure, quasi two-dimensional(2D) halide perovskite has more intriguing spin related physics than its 3D counterpart. For instance, the detection and brightening of dark exciton (DX) in 2D halide perovskite attracts much attention since these species can be used in opto-spintronic and quantum computing devices. Here, we report the gradually brightened emission of the DX at 2.…
Two-dimensional molybdenum disulphide on graphene grown by chemical vapour deposition is a promising van der Waals system for applications in optoelectronics and catalysis. To extend the fundamental understanding of growth and intrinsic properties of molybdenum disulphide on graphene, molybdenum disulphide on highly oriented pyrolytic graphite is a suitable model system. Here we show, experimentally and by density-functional-theory calculations, that molybdenum disulphide flakes grow in two orientations. One of the orientations is energetically preferred, the other one is rotated by 30 degree.…
Tailoring magnetism of nanographenes via tip-controlled dehydrogenation
Empa—Swiss Federal Laboratories for Materials Science and Technology（瑞士联邦材料科技研究院）；Technical University of Dresden（德累斯顿工业大学）；University of Zurich（苏黎世大学）；University of Bern（伯尔尼大学）；Max Planck Institute of Microstructure Physics（马克斯·普朗克微观结构物理研究所）
This study investigates the strong photoluminescence (PL) and X-ray excited optical luminescence observed in nitrogen-functionalized 2D graphene nanoflakes (GNFs:N), which arise from the significantly enhanced density of states in the region of π states and the gap between π and π* states. The increase in the number of the sp2 clusters in the form of pyridine-like N-C, graphite-N-like, and the C=O bonding and the resonant energy transfer from the N and O atoms to the sp2 clusters were found to be responsible for the blue shift and the enhancement of the main PL emission feature. The enhanced P…
Tailoring the Optoelectronic, Photocatalytic, Thermoelectric and Thermodynamic Properties of Halides Li2InBiX6 (X = Cl, Br, I) for Energy Conversion: A DFT Study
Princess Nourah Bint Abdulrahman University（公主诺拉·宾特·阿卜杜勒拉赫曼大学）；University of West Bohemia（西波希米亚大学）；University of Sargodha（萨尔戈达大学）；King Saud University（沙特国王大学）；Gachon University（迦南大学）
As device miniaturization approaches the atomic limit, it becomes highly desirable to exploit novel paradigms for tailoring electronic structures and carrier dynamics in materials. Elastic strain can in principle be applied to achieve reversible and fast control of such properties, but it remains a great challenge to create and utilize precisely controlled inhomogeneous deformation in semiconductors. Here, we take a combined experimental and theoretical approach to demonstrate that elastic strain-gradient can be created controllably and reversibly in ZnO micro/nanowires. In particular, we show…
The bulk photovoltaic effect that is intimately associated with crystalline symmetry has been extensively studied in various nonmagnetic materials, especially ferroelectrics with a switchable electric polarization. In order to further engineer the symmetry, one could resort to spin-polarized systems possessing an extra magnetic degree of freedom. Here, we investigate the bulk photovoltaic effect in two-dimensional magnetic sliding ferroelectric (MSFE) systems, illustrated in VSe2, FeCl2, and CrI3 bilayers. The transition metal elements in these systems exhibit intrinsic spin polarization, and …
Two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDCs) and black phosphorus (BP) have beneficial electronic, optical, and physical properties at the few-layer limit. As atomically thin materials, 2D TMDCs and BP are highly sensitive to their environment and chemical modification, resulting in a strong dependence of their properties on substrate effects, intrinsic defects, and extrinsic adsorbates. Furthermore, the integration of 2D semiconductors into electronic and optoelectronic devices introduces unique challenges at metal-semiconductor and dielectric-semiconductor int…
Tailoring structural, electronic, optical, and magnetic properties of rare-earth gallates RGaO$_3$ (R = Ho, Er, Tm) via first-principles investigations
Qilu Institute of Technology（齐鲁理工学院）；Kohat University of Science and Technology (KUST)（科哈特科学与技术大学）；University of Science & Technology Bannu（班努科技大学）；Shandong University（山东大学）
本研究通过第一性原理计算，系统研究了稀土镓酸盐RGaO$_3$（R=Ho, Er, Tm）的结构、电子、光学和磁性质，发现ErGaO$_3$为半导体，HoGaO$_3$和TmGaO$_3$为半金属，并具有自旋选择性光学激发和高反射率等特性，适用于自旋电子学和光电子学应用。
Oligothiophenes are pi-conjugated semiconducting and fluorescent molecules whose self-assembly properties are widely investigated for application in organic electronics, optoelectronics, biophotonics and sensing. We report here an approach to the preparation of crystalline oli-gothiophene nano/micro-fibers based on the use of a sulfur overrich quaterthiophene building block, -T4S4-, containing in its covalent network all the information needed to promote the di-rectional, pi-pi stacking driven, self-assembly of Ar-T4S4-Ar oligomers into fibers with hierar-chical supramolecular arrangement from…
Dopant-induced modifications of the optical properties of GaSe
Faculty of Physics, University of Warsaw（华沙大学物理学院）；Advanced Materials Research Group, Faculty of Engineering, University of Nottingham（诺丁汉大学工程学院先进材料研究组）；Institute for Problems of Material Science, National Academy of Sciences of Ukraine（乌克兰国家科学院材料科学问题研究所）
Semiconductor coupled quantum dots provide a unique opportunity of tuning bandgaps by tailoring band offsets, making them ideal for photovoltaic and other applications. Here, we have studied stability, trends in the band gap, band offsets, and optical properties for a series of coupled quantum dots comprised of II-VI semiconductor using a hybrid functional method. We have shown how the quantum confinement and interfacial strain considerably affect the band gap and band offsets for these heterostructures at the nanoscale. We show that the trend in band offsets obtained from our first-principles…
Tailoring electronic and optical properties of self-assembled InAs quantum dots (QDs) is a critical limit for the design of several QD-based optoelectronic devices operating in the telecom frequency range. We describe how a fine control of the strain-induced surface kinetics during the growth of vertically-stacked multiple layers of QDs allow to engineer their self organization process. Most noticeably, the present study shows that the underlying strain field induced along a QD stack can be modulated and controlled by time-dependent intermixing and segregation effects occurring after capping w…
Twisting in bilayers introduces structural chirality with two enantiomers, i.e., left- and right-hand bilayers, depending on the oriented twist angle. The interplay between this global chirality and additional degrees of freedom, such as magnetic ordering and the local octahedral chirality arising from the geometry of the bonds, can yield striking phenomena. In this work, we focus on collinear antiferromagnetic CrI$_3$ twisted homo-bilayers, which are characterized by a staggered octahedral chirality in each monolayer. Using symmetry analysis, density functional theory and tight-binding model …
The magnetic and electronic properties of strontium titanate with different carbon dopant configurations are explored using first-principles calculations with a generalized gradient approximation (GGA) and the GGA+U approach. Our results show that the structural stability, electronic properties and magnetic properties of C-doped SrTiO3 strongly depend on the distance between carbon dopants. In both GGA and GGA+U calculations, the doping structure is mostly stable with a nonmagnetic feature when the carbon dopants are nearest neighbors, which can be ascribed to the formation of a C-C dimer pair…
Localized Exciton Emission with Spontaneous Circular Polarization in NiPS3/WSe2 Heterostructures
Technion（以色列理工学院）；Bar-Ilan University（巴伊兰大学）；Technical University of Darmstadt（达姆施塔特工业大学）；University of Warsaw（华沙大学）；Technische Universität Dresden（德累斯顿工业大学）；Helmholtz-Zentrum Dresden-Rossendorf, Center for Advanced Systems Understanding, CASUS（德累斯顿-罗斯多夫亥姆霍兹中心，先进系统理解中心，CASUS）；Yonsei University（延世大学）
Spin-canting-induced Giant Nonlinear Optical Magnetochirality in a 2D Ferrotoroid
Wuhan University（武汉大学）；Huazhong University of Science & Technology（华中科技大学）；National University of Singapore（新加坡国立大学）；National University of Singapore Suzhou Research Institute（新加坡国立大学苏州研究院）
Plasmonic Metasurfaces for Magnetic Skyrmion Control via the Inverse Faraday Effect
Sorbonne Université, CNRS, Institut des NanoSciences de Paris, INSP（索邦大学，法国国家科学研究中心，巴黎纳米科学研究所）；School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology（大连理工大学光电工程与仪器科学学院）；Instituto de Engenharia de Sistemas E Computadores – Microsistemas e Nanotecnologias (INESC MN)（系统计算机工程研究所-微系统与纳米技术）；Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain（天主教鲁汶大学凝聚态与纳米科学研究所）；School of Electronic and Information Engineering, Ningbo University of Technology（宁波理工学院电子与信息工程学院）；Blackett Laboratory, Department of Physics, Imperial College London（伦敦帝国理工学院物理系布莱克特实验室）；London Centre for Nanotechnology, Imperial College London（伦敦帝国理工学院伦敦纳米技术中心）；Laboratoire Albert Fert, CNRS, Thales, Université Paris-Saclay（巴黎萨克雷大学CNRS-Thales阿尔伯特·费尔特实验室）
