Highly Efficient Second/Third Harmonic Generation in van der Waals Layered Material AgScP2S6 with Anisotropic Polarization and Temperature Dependence
The Ohio State University（俄亥俄州立大学）；the University of Texas at Dallas（德克萨斯大学达拉斯分校）；ELI ALPS, ELI-HU Non-Profit Ltd.（ELI ALPS，匈牙利ELI非营利有限公司）；Materials and Manufacturing Directorate, Airforce Research Laboratory（空军研究实验室材料与制造管理局）；Azimuth Corporation（Azimuth公司）；Core4ce LLC（Core4ce有限责任公司）
Mohamed Yaseen Noor, Ryan Siebenaller, Wenhao Liu, Zixin Zhai, Conrad Kuz, Simin Zhang, Mousumi Upadhyay Kahaly, Gergely Nagy, Aamir Mushtaq, Rahul Rao, Emmanue… 展开作者
Mohamed Yaseen Noor, Ryan Siebenaller, Wenhao Liu, Zixin Zhai, Conrad Kuz, Simin Zhang, Mousumi Upadhyay Kahaly, Gergely Nagy, Aamir Mushtaq, Rahul Rao, Emmanuel Rowe, Benjamin S. Conner, Bing Lv, Michael A. Susner, Enam Chowdhury
Single-crystal X-ray diffraction and nonlinear optical measurements, especially second- and third-harmonic generation (SHG/THG) are comprehensively investigated for the van der Waals layered material AgScP2S6 with a non-centrosymmetric P31c (159) space group. Linear optical constants are extracted using spectroscopic ellipsometry and applied in fitting the harmonic generation behavior. Polarization-resolved SHG and THG measurements exhibit pronounced anisotropy, with emission patterns well-described by theoretical models derived from the khi(2) and khi(3) tensor elements. The material demonstrates exceptionally high nonlinear susceptibilities, with khi(2) ~ 10^(-8) m/V and khi(3) ~ 10^(-17) m^2/V^2 which is a few orders of magnitude greater than comparable 2D materials reported in the literature. Temperature-dependent SHG and THG measurements from 300 K to 25 K reveal exponential decay in harmonic signal intensities, attributed to reduced carrier mobility, with no evidence of structural phase transitions, consistent with results from single crystal diffraction and heat capacity measurements. Polarization-resolved SHG and THG measurements also reveal distinct orientation and ellipticity trends, highlighting the anisotropic nonlinear tensor contributions and contrasting polarization selection rules in the material. These results establish AgScP2S6 as a high-performance, thermally stable, and highly anisotropic nonlinear candidate material suitable for compact photonic applications such as ultrafast optical modulators, polarization-sensitive detectors, and wavelength-tunable light sources.
Using high-throughput first-principles calculations to search for layered van der Waals materials with the largest piezoelectric stress coefficients, we discover NbOI2 to be the one among 2940 monolayers screened. The piezoelectric performance of NbOI2 is independent of thickness, and its electromechanical coupling factor of near unity is a hallmark of optimal interconversion between electrical and mechanical energy. Laser scanning vibrometer studies on bulk and few-layer NbOI2 crystals verify their huge piezoelectric responses, which exceed internal references such as In2Se3 and CuInP2S6. Fur…
Electrically-Tunable High Curie Temperature Two-Dimensional Ferromagnetism in Van der Waals Layered Crystals
识别具有高转变温度和电可调磁性的本征低维铁磁体对于小型化自旋电子学和磁电学的发展至关重要。最近在范德华晶体CrI $_3$和Cr $_2$ Ge $_2$ Te $_6$中观察到了长程二维铁磁性，然而当减小到单层/几层时，它们的居里温度显著降低。本文利用重整化自旋波理论和第一性原理电子结构理论，对具有较高居里温度（~ 150 K）和较大带隙的van der Waals层状CrSBr和CrSeBr半导体的电调谐二维铁磁性进行了理论研究。高转变温度归因于强阴离子介导的超交换相互作用和由于大交换和单离子各向异性而引起的相当大的自旋波激发间隙。值得注意的是，空穴和电子掺杂可以将磁化易轴从面内方向切换到面外方向。这些独特的特性使单层CrSBr和CrSeBr成为实现2D自旋电子学和磁电学的有前途的平台，例如2D自旋场效应晶体管。
A broad family of the nowadays studied low-dimensional systems, including 2D materials, demonstrate many fascinating properties, which however depend on the atomic composition as well as on the system dimensionality. Therefore, the studies of the electronic correlation effects in the new 2D materials is of paramount importance for the understanding of their transport, optical and catalytic properties. Here, by means of electron spectroscopy methods in combination with density functional theory calculations we investigate the electronic structure of a new layered van der Waals FePX$_3$ (X: S, S…
We report the crystal growth and structural and electronic properties of superconducting, van der Waals layered PtTe. Easily cleavable crystals with a plate-like morphology consistent with the layered structure were grown from a platinum rich flux. A consistent determination of $T_c = 0.57$ K is made from the onset of diamagnetism, the zero of resistivity, and the midpoint of the heat capacity jump. The observed behavior is consistent with type-II superconductivity, with upper critical field at $T=0$ estimated using the Werthamer-Helfand-Hohenberg theory to be 143 and 65 Oe for fields out of a…
The exfoliation of layered magnetic materials generates atomically thin flakes characterized by an ultrahigh surface sensitivity, which makes their magnetic properties tunable via external stimuli, such as electrostatic gating and proximity effects. Another powerful approach to tailor magnetic materials is molecular functionalization, which leads to hybrid interface states with peculiar magnetic properties, called spinterfaces. However, spinterface effects have not yet been explored on layered magnetic materials. Here, we demonstrate the emergence of spinterface effects at the interface betwee…
When two-dimensional van der Waals materials are stacked to build heterostructures, moiré patterns emerge from twisted interfaces or from mismatch in lattice constant of individual layers. Relaxation of the atomic positions is a direct, generic consequence of the moiré pattern, with many implications for the physical properties. Moiré driven atomic relaxation may be naively thought to be restricted to the interfacial layers and thus irrelevant for multi-layered heterostructures. However, we provide experimental evidence for the importance of the three dimensional nature of the relaxation in tw…
Electric-field control of magnetism in few-layered van der Waals magnet
利用静电门技术操纵量子态是纳米电子学中许多模型系统的研究热点。当涉及到控制电子自旋的问题时，更具体地说，系统的磁性，用电场调谐已被证明是难以捉摸的。近年来，磁性层状半导体由于其新的物理现象而引起了人们的广泛关注。然而，在基于它们的栅极可控磁性的演示中仍然存在挑战。在这里，我们表明，通过离子门控，可以观察到强场效应在几层半导体Cr $_{2}$ Ge $_{2}$ Te $_{6}$设备。在不同的栅极掺杂，在所研究的设备中的微区克尔测量表明可调谐的磁化循环低于居里温度，这是暂时归因于自旋极化的能带结构的力矩重新平衡。我们在范德华磁体中的电场控制磁性的发现为新一代磁存储器、传感器和自旋电子学的潜在应用铺平了道路。
The van der Waals layered material CuInP2S6 features interesting functional behavior, including the existence of four uniaxial polarization states, polarization reversal against the electric field through Cu ion migration, a negative-capacitance regime, and reversible extraction of Cu ions. At the heart of these characteristics lies the high mobility of Cu ions, which also determines the spontaneous polarization. Therefore, Cu migration across the lattice results in unusual ferroelectric behavior. Here, we demonstrate how the interplay of polar and ionic properties provides a path to ionically…
Layered materials can possess valleys that are indistinguishable from one another except for the momentum. These valleys are individually addressable in momentum space at the K and K' points in the first Brillouin zone. Such valley addressability opens up the possibility of utilizing the momentum state of quasi-particles as a completely new paradigm in quantum and classical information processing. This review focuses on the physics behind valley polarization and talks about carriers of valley degree of freedom (VDF) in layered materials. Then we provide a detailed survey of simple spectroscopi…
Role of van der Waals bonding in layered oxide: Bulk vanadium pentoxide
稀疏物质的特征在于具有低电子密度的区域，并且其理解要求精确计算范德华（vdW）相互作用和其他键合的方法。在这里，我们提出了一个第一性原理密度泛函理论（DFT）研究的层状氧化物（V2 O 5）的散装结构，其中显示电荷空隙之间的层，我们强调的作用的VDW部队在建立材料的凝聚力。以前的第一性原理研究的结果涉及半局部近似的交换相关功能的DFT给出的结果与实验的两个面内晶格参数的晶胞，但高估了参数的堆叠方向。为了恢复第三个参数，我们通过vdW-DF方法包括非局部（色散）vdW相互作用[Dion等人，物理修订版信函92，246401（2004）]还测试交换风味的各种选择。我们发现，可转移的第一性原理vdw-DF计算稳定的散装结构。的vdw-DF方法给出的结果与实验的所有三个晶格参数相当好的协议。
Intrinsic magnetic topological insulators in van der Waals layered MnBi$_2$Te$_4$-family materials
磁性与拓扑学的相互作用是凝聚态物理和材料科学的重要研究课题，它为探索量子反常霍尔效应、轴子电动力学和马约拉纳费米子等新兴物理提供了巨大的机会。然而，由于缺乏合适的工作材料，这些奇异的物理效应在实验中很少实现。在这里，我们预测，范德华层状MnBi $_2$ Te $_4$ -家庭材料显示二维（2D）铁磁性在单层和三维（3D）$A$型反铁磁性在块体，这可以作为一个新一代的材料平台，为国家的最先进的研究。值得注意的是，我们预测非常丰富的拓扑量子效应与突出的功能，在实验可用的材料MnBi $_2$ Te $_4$，包括3D反铁磁拓扑绝缘体与长期寻求的拓扑轴子状态，II型磁性Weyl半金属（WSM）与简单的一对Weyl点，和高温本征QAH效应。这些惊人的预测，如果实验证明，可能会深刻地改变拓扑量子物理学的未来研究和技术。
The discovery of an ever increasing family of atomic layered magnetic materials, together with the already established vast catalogue of strong spin-orbit coupling (SOC) and topological systems, calls for some guiding principles to tailor and optimize novel spin transport and optical properties at their interfaces. Here we focus on the latest developments in both fields that have brought them closer together and make them ripe for future fruitful synergy. After outlining fundamentals on van der Waals (vdW) magnetism and SOC effects, we discuss how their coexistence, manipulation and competitio…
Controlling magnetism in low dimensional materials is essential for designing devices that have feature sizes comparable to several critical length scales that exploit functional spin textures, allowing the realization of low-power spintronic and magneto-electric hardware. [1] Unlike conventional covalently-bonded bulk materials, van der Waals (vdW)-bonded layered magnets [2-4] offer exceptional degrees of freedom for engineering spin textures. [5] However, their structural instability has hindered microscopic studies and manipulations. Here, we demonstrate nanoscale structural control in the …
Identifying Highly Deformable van der Waals Layered Chalcogenides with Superior Thermoelectric Performance Using Deformability Factors and Interpretable Machine Learning
Recently, the two-dimensional magnetic semiconductor CrSBr has attracted considerable attention due to its excellent air-stable property and high magnetic critical temperature. Here, we systematically investigate the electronic structure, magnetocrystalline anisotropy energy, first-order magneto-optical effects (Kerr and Faraday effects) and second-order magneto-optical effects (Schafer-Hubert and Voigt effects) as well as intrinsically anomalous transport properties (anomalous Hall, anomalous Nernst, and anomalous thermal Hall effects) of two-dimensional van der Waals layered magnets CrXY (X …
The quasi-two-dimensional antiferromagnet Ni$_2$P$_2$S$_6$ belongs to the family of magnetic van der Waals compounds that provides a rich material base for the realization of fundamental models of quantum magnetism in low dimensions. Here, we report high-frequency/high-magnetic field electron spin resonance measurements on single crystals of Ni$_2$P$_2$S$_6$. The results enable one to reliably determine the positive, "easy"-plane type of the single ion anisotropy of the Ni$^{2+}$ ions with the upper limit of its magnitude $\lesssim 0.7$ meV. The resonance response reveals strongly anisotropic …
Excitons in van der Waals materials: from monolayer to bulk hexagonal boron nitride
我们提出了一个一般的图片的激子性质的层状材料的单层积木的激发。为此，我们推导出一个模型激子哈密顿绘制一个类比与分子晶体，这是其他原型范德华材料。我们采用这个简化模型详细分析了六方氮化硼（hBN）的激发光谱，我们已经从多体Bethe-Salpeter方程的{ \it ab initio}解作为动量的函数得到。通过这种方法，我们确定了hBN中最低能量激子的性质，讨论了层间跳跃和电子-空穴交换相互作用对激子色散的影响，阐明了层状材料中激子与等离子体激元之间的关系。
Stacking and Registry Effects in Layered Materials: The Case of Hexagonal Boron Nitride
采用van der Waals修正的密度泛函理论方法研究了六方氮化硼（h-BN）的层间滑移能谱.结果表明，范德华力的主要作用是将层间固定在一个固定的距离上，而静电力则决定了最佳的堆积模式和层间滑动能。一个几乎自由滑动的路径被确定，沿着该路径获得~0.6 eV的带隙调制。我们提出了一个简单的几何模型，量化层之间的注册表匹配，并捕捉波纹h-BN层间能量景观的本质。这种现象学模型的简单性为复杂的层状结构（如碳和氮化硼纳米管）的建模开辟了道路。
