Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session R32: Computational Discovery and Design of Novel Materials IX |
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Sponsoring Units: DMP DCOMP Chair: Hai-Ping Cheng, University of Florida Room: 295 |
Thursday, March 16, 2017 8:00AM - 8:12AM |
R32.00001: Abstract Withdrawn
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Thursday, March 16, 2017 8:12AM - 8:24AM |
R32.00002: Transport properties of two-dimensional metal-phthalocyanine junctions: An ab initio study Shuang-Long Liu, Yun-Peng Wang, Xiang-Guo Li, Hai-Ping Cheng We study two dimensional (2D) electronic/spintronic junctions made of metal-organic frameworks via first-principles simulation. The system consists of two Mn-phthalocyanine leads and a Ni-phthalocyanine center. A 2D Mn phthalocyanine sheet is ferromagnetic half metal and a 2D Ni phthalocyanine sheet is nonmagnetic semiconductor. Our results show that this system has a large tunnel magnetic resistance. The transmission coefficient at Fermi energy decays exponentially with the length of the central region which is not surprising. However, the transmission of the junction can be tuned using gate voltage by up to two orders of magnitude. The origin of the change lies in the mode matching between the lead and the center electronic states. Moreover, the threshold gate voltage varies with the length of the center region which provides a way of engineering the transport properties. Finally, we combine non-equilibrium Green’s function and Boltzmann transport equation to compute conductance of the junction. [Preview Abstract] |
Thursday, March 16, 2017 8:24AM - 8:36AM |
R32.00003: Quantum anomalous Hall effect in ferromagnetic Ru iodide monolayer. Jian Zhou, Chengxi Huang, Erjun Kan, Puru Jena Based on the successful synthesis of transition metal halides, we use first-principles calculations to predict that RuI$_{\mathrm{3}}$ monolayer is an intrinsic ferromagnetic QAH insulator with a topologically nontrivial global band gap of 11 meV. The band structure of RuI$_{\mathrm{3}}$ monolayer shows a Dirac cone in the spin down channel, while the spin up channel is insulating. When the spin-orbit coupling is included, the Dirac cone opens a finite band gap. This topologically nontrivial band gap at the Fermi level is due to its crystal symmetry, thus the QAH effect is robust. Its Curie temperature, estimated to be \textasciitilde 360 K using Monte-Carlo simulation, is above room temperature and higher than most of two-dimensional ferromagnetic thin films. We also discuss the manipulation of its exchange energy and nontrivial band gap by applying in-plane strain. This work adds a new experimentally feasible member to the QAH insulator family, which is expected to have broad applications in nanoelectronics and spintronics. Detailed information can be found in https://arxiv.org/pdf/1609.08115. [Preview Abstract] |
Thursday, March 16, 2017 8:36AM - 8:48AM |
R32.00004: Stability and magnetism in FeC$_{\mathrm{2}}$ monolayer Tianshan Zhao, Jian Zhou, Qian Wang, Yoshiyuki Kawazoe, Puru Jena We report a new FeC$_{\mathrm{2}}$ sheet containing C$_{\mathrm{2}}$ dimers, which can be chemically exfoliated from bulk ThFeC$_{\mathrm{2}}$ phase. Using density functional theory combined with AIMD and phonon dispersion calculation, we found that upon exfoliation from bulk ThFeC$_{\mathrm{2}}$, the FeC$_{\mathrm{2}}$ sheet changes its symmetry from \textit{Amm}2 to \textit{Pmmn}, while retaining its robust dynamical, thermal and mechanical stability. In sharp contrast to the metallic and paramagnetic bulk phase of ThFeC$_{\mathrm{2\thinspace }}$and the recently reported TiC$_{\mathrm{2}}$ sheet,$_{\mathrm{\thinspace }}$the$_{\mathrm{\thinspace }}$exfoliated FeC$_{\mathrm{2}}$ sheet$_{\mathrm{\thinspace }}$is half-metallic and ferromagnetic with a Curie-temperature of 245 K, making it a promising candidate for spintroinc applications. [Preview Abstract] |
Thursday, March 16, 2017 8:48AM - 9:00AM |
R32.00005: Computational design of a novel two dimensional InP nanostructure Congyan Zhang, Ming Yu A novel two dimensional (2D) InP nanostructure was predicted through computational simulation on the base of the density functional theory. A monolayer InP sheet was initially designed by substituting indium atoms in phosphorene alternatively. This monolayer InP sheet was then stabilized from the initial puckered honeycomb lattice to a buckled honeycomb lattice with C$_{\mathrm{1H}}$ symmetry. Its stability has been confirmed by studying its phonon spectrum. Especially, it was found that its total energy is about 0.09 eV/atom lower than the previously predicted buckled honeycomb InP sheet with C$_{\mathrm{3V}}$ symmetry [Phys. Rev. B 80, 155453 (2009)], clearly demonstrating that 2D InP nanostructure will prefer to stay with C$_{\mathrm{1H}}$ symmetry. More interestingly, this newly discovered InP sheet possesses semiconducting nature with a direct bandgap of 1.72 eV. [Preview Abstract] |
Thursday, March 16, 2017 9:00AM - 9:12AM |
R32.00006: Monolayer II-VI semiconductors: A first-principles prediction Hui Zheng, Nian-Ke Chen, S. B. Zhang, Xian-Bin Li A systematic study of 32 honeycomb monolayer II-VI semiconductors is carried out by first-principles methods. It appears that BeO, MgO, CaO, ZnO, CdO, CaS, SrS, SrSe, BaTe, and HgTe honeycomb monolayers have a good dynamic stability which is revealed by phonon calculations. In addition, from the molecular dynamic (MD) simulation of other unstable candidates, we also find two extra monolayers dynamically stable, which are tetragonal BaS and orthorhombic HgS. The honeycomb monolayers exist in form of either a planar perfect honeycomb or a low-buckled 2D layer, all of which possess a band gap and most of them are in the ultraviolet region. Interestingly, the dynamically stable SrSe has a gap near visible light, and displays exotic electronic properties with a flat top of the valence band, and hence has a strong spin polarization upon hole doping. The honeycomb HgTe has been reported to achieve a topological nontrivial phase under appropriate in-plane tensile strain and spin-orbital coupling (SOC). Some II-VI partners with less than 5{\%} lattice mismatch may be used to design novel 2D heterojunction devices. If synthesized, potential applications of these 2D II-VI families could include optoelectronics, spintronics, and strong correlated electronics. [Preview Abstract] |
Thursday, March 16, 2017 9:12AM - 9:24AM |
R32.00007: First-principles Prediction of Thermodynamically Stable Two-Dimensional Electrides Mina Yoon, Wenmei Ming, Mao-Hua Du, Kimoon Lee, Sung Wng Kim Two-dimensional (2D) electrides, emerging as a new type of layered material whose electrons are confined in interlayer spaces instead of at atomic proximities, are receiving interest for their high performance in various (opto)electronics and catalytic applications. Experimentally, however, 2D electrides have been only found in a couple of layered nitrides and carbides. Here, we report new thermodynamically stable alkaline-earth based 2D electrides by using a first-principles global structure optimization method, phonon spectrum analysis, and molecular dynamics simulation. The method was applied to binary compounds consisting of alkaline-earth elements as cations and group VA, VIA, or VIIA nonmetal elements as anions. We revealed that the stability of layered 2D electride structure is closely related to the cation/anion size ratio; stable 2D electrides possess a sufficiently large cation/anion size ratio to minimize electrostatic energy among cations, anions, and anionic electrons. Our work demonstrates a new avenue to the discovery of thermodynamically stable 2D electrides beyond experimental material databases and provides new insight into the principles of electride design. [Preview Abstract] |
Thursday, March 16, 2017 9:24AM - 9:36AM |
R32.00008: Discovery of novel functional 2D materials via a 2D materials database Jinbo Pan, Haowei Peng, Jie Yu, John Perdew, Qimin Yan Single-layer two-dimensional (2D) materials offer great new opportunities for the discovery and design of new functionalities in this compound space. In this work, we construct a comprehensive single-layer 2D materials database based on a data-driven approach. More than 1000 compounds with layered structures have been identified through a data-mining process in the ICSD material database, upon which single-layer structures are constructed. High-throughput computations based on density functional theory (DFT) with the PBE and newly developed SCAN functionals are performed to optimize the geometric structures. Electronic structures of these materials are evaluated using the PBE, SCAN, and HSE06 functionals. Key materials properties are stored in the database, which offers a great opportunity for the rational design of functional 2D materials for technical applications including solar fuel conversion, topological materials, electronics, and catalysis. As a showcase, we hope to present the discovery of novel 2D topological and energy materials. The work was supported as part of the Center for the Computational Design of Functional Layered Materials, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science. [Preview Abstract] |
Thursday, March 16, 2017 9:36AM - 9:48AM |
R32.00009: Biexcitons in a transition metal dichalcogenide monolayer Shalva Tsiklauri, Roman Kezerashvili The light emission measurements of biexcitons introduced inconsistency between theory and experiment. This significant disagreement between the experimental results and the theoretical calculations is known as the "biexciton puzzle". We suggest a new theoretical analysis of 2D biexcitons in the framework of the method of hyperspherical harmonics for solving four body Schr\"{o}dinger equation [1]. We assume that electrons and holes are interacted via Keldysh potential [2]. The convergence of binding energy of the ground state of the bioexciton as a function of the grand angular momentum is studied. For the biexcitons binding energy in MoS$_{\mathrm{2}}$ we obtain \textasciitilde 20 meV. This value is remarkably close to the experimental value [3]. A comparison with results of other calculations is presented. We also study solutions of a hyperradial equation in a minimal approximation for the ground angular momentum to examine two regimes: a long range and a short range cases when the inter particle distance is much greater and much less than the screening length. For these cases, we find analytical expressions for the energy and wave function for biexciton states. 1. R. Ya. Kezerashvili, Sh. M. Tsiklauri,. Few-Body Syst. 54, 1653, (2013). 2. L.V.Keldysh, JETP Lett. \textbf{29},658, (1979). 3. Kai Hao, Lixiang Xu, Judith F. Specht et. al. arXiv:1609.02008. This research is supported by PSC- CUNY Grant: {\#} PSC-CUNY Award {\#} 69536-00 47 [Preview Abstract] |
Thursday, March 16, 2017 9:48AM - 10:00AM |
R32.00010: Electronic and thermodynamic properties of layered \textbf{\textit{Hf}}$_{\mathbf{2}}$\textbf{\textit{S}}\textbf{ from first-principles calculations} Chandani Nandadasa, Mina Yoon, Seong-Gon Kim, Steve Erwin, Sungho Kim, Sung Wng Kim, Kimoon Lee Theoretically we explored two stable phases of inorganic fullerene-like structure of the layered dihafnium sulfide (\textit{Hf}$_{2}S)$. We investigated structural and electronic properties of the two phases of \textit{Hf}$_{2}S$ by using first-principles calculations. Our calculation identifies experimentally observed anti-\textit{ NbS}$_{2}$ structure of \textit{Hf}$_{2}S$. Our electronic calculation results indicate that the density of states of anti- \textit{NbS}$_{2}$ structure of \textit{Hf}$_{2}S$ at fermi level is less than that of the other phase of \textit{Hf}$_{2}S$. To study the relative stability of different phases at finite temperature Helmholtz free energies of two phases are obtained using density functional theory and density functional perturbation theory. The free energy of the anti-\textit{ NbS}$_{2}$ structure of \textit{Hf}$_{2}S$ always lies below the free energy of the other phase by confirming the most stable structure of \textit{Hf}$_{2}S$. The phonon dispersion, phonon density of states including partial density of states and total density of states are obtained within density functional perturbation theory. Our calculated zero-pressure phonon dispersion curves confirm that the thermodynamic stability of \textit{Hf}$_{2}S$ structures. For further investigation of thermodynamic properties, the temperature dependency of thermal expansion, heat capacities at constant pressure and volume are evaluated within the quasiharmonic approximations (QHA). [Preview Abstract] |
Thursday, March 16, 2017 10:00AM - 10:12AM |
R32.00011: Revealing Quasi-Two-Dimensional Metallicity in a Layered Chalcogenide Ti$_{\mathrm{2}}$PTe$_{\mathrm{2}}$ Ji Seop Oh, Ho-Sung Yu, Chang-Jong Kang, Soobin Sinn, Moonsup Han, Young Jun Chang, Byeong-Gyu Park, Kimoon Lee, Byung Il Min, Sung Wng Kim, Hyeong-Do Kim, Tae Won Noh Transition metal chalcogenides (TMCs) have been attracting broad interest among physicists and material scientists because of their physical properties leading to high potential for applications. Most studies have been focused on semiconducting binary TMCs, but studies on metallic or ternary TMCs are relatively rare. Recently, ternary TMCs is expected to enlarge the scope of research on TMCs because they show distinguishable properties from binary semiconducting TMCs. Here, we studied how quasi-two-dimensional (2D) metallicity evolves in a ternary layered chalcogenide Ti$_{\mathrm{2}}$PTe$_{\mathrm{2}}$ (TPT). Temperature-dependent resistivity shows a metallic character with two types of carriers in quasi-2D nature. To investigate the origin of the metallicity, we experimentally and theoretically studied the electronic structure of TPT. Fermi surfaces of TPT in the first Brillouin zone have quasi-2D electron pockets and a small three-dimensional hole pocket, which agrees with the transport results. We also present theoretical calculations to compare with the experimental results. The calculations are well matched with the experimental results, and it suggests that quasi-2D metallicity originates from Ti 3$d$ orbitals. [Preview Abstract] |
Thursday, March 16, 2017 10:12AM - 10:24AM |
R32.00012: Mechanical Modulation of Tunneling Current in Transition Metal Dichalcogenides Heterostructures: A First Principles Study Marcelo Kuroda Recent experiments in MoS$_2$ heterostructures reported that out-of-plane tunneling piezoresistivity (TPR) -- mechanical modulation of the tunneling current -- achieves sensitivities of one decade per \AA~displacement. Owing to their nanometer scale, a quantitative theoretical framework providing the TPR structure-property relationship is necessary to further improve sensitivities. To this end, first principles calculations within density functional theory are used to characterize the phenomenon in Mo$X_2$ (with $X$ = S, Se). The TPR is quantified in relation to electrode composition and film thickness showing remarkable agreement with experiments. The origin of the TPR is attributed to the heterostructure compliance rather than band alignment changes with strain, and differs from mechanisms in other nanometer-thick bulk films. Large work function metals (Pt, Au) are singled out as best candidates for enhanced TPR gauges due to weak bonding and negligible thermionic emission; compliant bilayers show larger stress-sensitivity than monolayers. By accounting for the atomistic details and material composition of 2D material-based heterostructures, this work has the potential to advance sensor and nano-electro-mechanical system technologies. [Preview Abstract] |
Thursday, March 16, 2017 10:24AM - 10:36AM |
R32.00013: Band-structure effects in vertical layered-material heterostructures Gabriel Constantinescu, Nicholas Hine By stacking 2D materials one can fine-tune the electronic structure properties of the component layers. We employ high-accuracy linear-scaling DFT calculations to explore large-scale models of transition metal dichalcogenide (TMDC) and hBN/Phosphorene heterostructures. Band modifications upon stacking and rotation of different monolayers can be obtained by unfolding the supercell spectral function into the primitive cells, allowing direct comparison to experimental ARPES results. Changes in spectral weight and band-structure between the monolayers and heterostructured interfaces show how lattice mismatch (TMDC/TMDC) or spacer layers (Phosphorene/hBN/Phosphorene) allow the component monolayers to retain more independence in heterostructures than in homo-stacks. Moreover, one can envision using cavities in spacer layers in order to confine the radial extent of a vertical heterostructure, with potential applications in optoelectronics. [Preview Abstract] |
Thursday, March 16, 2017 10:36AM - 10:48AM |
R32.00014: Ab-initio study of heterostructures of vertically stacked and rotationally aligned incommensurate 2D-films Gianina Buda, Christopher Lane, Zachariah Hennighausen, Anthony Vargas, Fangze Liu, Ismail Bilgin, Daniel Rubin, Swastik Kar, Arun Bansil Heterostructures obtained through vertical stacking of atomically-thin films are expected to provide a new generation of materials platforms for fundamental science investigations as well as applications. We discuss how one Bi$_2$Se$_3$ quintuple-layer (QL) deposited on an MoS$_2$ trilayer (TL) can stack aligned rotationally with long-range crystallographic order, despite the incommensurability of their lattices to form a new type of well-defined $heterocrystal$. Surprisingly, interaction between the Bi$_2$Se$_3$ and MoS$_2$ layers leads to electronic properties of the heterocrystal that are quite distinct from those of the parent films. We discuss our experimental findings in terms of first-principles computations of electronic and spin-structures, as well as charge densities for heterostructures of Bi$_2$Se$_3$ stacked layer-by-layer on MoSe$_2$ and WS$_2$ films. [Preview Abstract] |
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