Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session F15: Design of 2D Materials |
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Sponsoring Units: DCMP DMP Room: 314 |
Tuesday, March 15, 2016 11:15AM - 11:27AM |
F15.00001: Stable bound states of like charges on top of graphene in magnetic field Sergey Slizovskiy We show theoretically that in the external magnetic field like charges on top of graphene monolayer may be mutually attracted to form thermodinamically stable macro-molecules. For this to happen graphene needs to be in Quantum Hall plateau state with local chemical potential being between the Landau levels. Graphene electron(s) gets localized in the middle between charges and provides overscreening of Coulomb repulsion between the charges. The size of the resulting macro-molecules is of the order of the magnetic length ($\sim 10$ nm for magnetic field 10 T). The possible stable macro-molecules that unit charges can form on graphene in magnetic field are classified. The binding survives significant temperatures, exceeding mobility barriers for many ionically bond impurities. The influence of possible lattice-scale effects of valley-mixing are discussed. Tuning the doping of graphene or the magnetic field, the binding of impurities can be turned on and off and the macro-molecule size may be tuned. This opens the perspective to nanoscopic manipulation of ions on graphene by using magnetic field and gating. [Preview Abstract] |
Tuesday, March 15, 2016 11:27AM - 11:39AM |
F15.00002: Ab initio study of magnetic single layer MPX3 metal-phosphorous-trichalcogenides Bheema Lingam Chittari, Euyheon Hwang, Jeil Jung, Allan H. MacDonald We analyze the electronic structure of two dimensional (2D) MPX3 (M= V, Cr, Mn, Fe, Co, Ni, Cu, Zn, and X = S, Se, Te) transition metal thiophosphates, viewing them as single layer van der Waals materials that can exhibit magnetic order. Our ab initio calculations for MPX3 single layer compounds predict both semiconducting phases with variable band gap sizes and metallic phases, and an intimate interplay between magnetic order and the presence of a gap. A systematic trend of decreasing band gaps in antiferromagnetic states is observed as the chalcogen atoms S, Se, and Te change from smaller to larger atomic number, Ferromagnetic, antiferromagnetic, and nonmagnetic phases, and lattice constant changes accompanied by distortions in crystal symmetry, occur as the metal atom is varied. The sensitive interdependence between magnetic, structural, and electronic properties suggests the important potential of this class of 2D magnetic van der Waals materials for strain and field-effect carrier tunable spintronics. [Preview Abstract] |
Tuesday, March 15, 2016 11:39AM - 11:51AM |
F15.00003: Anisotropic optical properties of few-layer transition metal dichalcogenide ReS$_2$ Zhenglu Li, Ting Cao, Felipe H. da Jornada, Meng Wu, Steven G. Louie We present first-principles (DFT, GW and GW-BSE) calculations of the electronic and optical properties of few-layer rhenium disulfide (ReS$_2$). Monolayer ReS$_2$ shows strong many-electron effects with a fundamental quasiparticle band gap of 2.38 eV based on G$_0$W$_0$ calculation and a large exciton binding energy of 690 meV based on solving the Bethe-Salpeter equation. Highly anisotropic linear-polarized optical absorptions are revealed for few-layer and bulk ReS$_2$. The band gap shows a decreasing trend with the optical polarization direction near the absorption edge gradually rotating from around 67 degree in the monolayer to 85 degree in the bulk, referencing to the Re-chain. Our calculations are consistent with recent experimental data and theoretical studies, and provide a systematic understanding of the electronic and optical properties in few-layer ReS$_2$. This work was supported by National Science Foundation Grant No. DMR15-1508412 and the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Computational resources have been provided by DOE at Lawrence Berkeley National Laboratory's NERSC facility. [Preview Abstract] |
Tuesday, March 15, 2016 11:51AM - 12:03PM |
F15.00004: Anisotropy in the optical properties of bulk and layered transition metal dichalcogenide ReS$_{2}$ Suvadip Das, Nihar Pradhan, Carlos Garcia, Daniel Rhodes, Stephen McGill, Luis Balicas, Efstratios Manousakis Unlike most transition metal dichalcogenides, ReS$_{2}$ in the distorted 1T$^{\prime}$ phase, is a direct gap semiconductor. We measured the temperature dependent photoluminescence in both bulk and layered ReS$_{2}$ and examined the evolution of the peaks with the number of layers. We obtained strong signatures of optical anisotropy in the absorption spectroscopy and photocurrent response which makes this material a potential candidate for optoelectronic applications. Many body calculations including electron-hole interactions as implemented in the GW+BSE approach, agrees with the strong anisotropy in the optical properties of bulk and monolayer ReS$_{2}$. A shift in the excitonic peaks by about 0.8 eV introduced by solving the Bethe-Salpeter equation indicates strong contribution from excitonic bound states in this transition metal dichalcogenide. [Preview Abstract] |
Tuesday, March 15, 2016 12:03PM - 12:15PM |
F15.00005: First-principles Study of Temperature Dependence of Energy Gap in 2D Materials Yuning Wu, Xiaoguang Zhang We use a first-principles method to study the temperature dependence of energy gap in 2D semiconductors, including monolayer MoS$_{2}$ and MoSe$_{2}$, \textit{etc}, due to the effect of phonons on the band structure. The phonon vibrations are modeled by a set of frozen-phonon configurations, in which atomic displacements are determined by the Bose-Einstein distribution of the phonon modes. The electronic structure is calculated for each configuration, and the energy gap is extracted from configurational statistics. Calculated temperature dependence of energy gap agrees with the photoluminescence experiments [1] in terms of both the values of the band gap as well as the line shapes. [1] S. Tongay \textit{et al}., Nano Lett. 12, 5576, (2012) [Preview Abstract] |
Tuesday, March 15, 2016 12:15PM - 12:27PM |
F15.00006: Ab initio studies of excitations in monolayer black phosphorus Tobias Frank, Marcin Kurpas, Martin Gmitra, Rene Derian, Ivan Stich, Jaroslav Fabian Monolayer black phosphorus, or phosphorene, represents an ideal system to study many-body electron-electron and electron-hole interactions due to its strong anisotropy driven 1d electronic nature. In particular, the size of the fundamental band gap value and excitonic binding energies remain unresolved given the different gap values of 1.6 to 2.4 eV [1] obtained by many-body GW calculations. We present our contribution to this issue studying excitations in phosphorene employing quantum monte carlo (QMC) calculations. We show the evolution of finite size effects of the fundamental and optical gap, with respect to relatively large supercell sizes in the theoretical framework of diffusion monte carlo (DMC) explicitly including electronic correlations. Our studies point to a significant influence of electron correlation on the fundamental gap as well as to a strong anisotropic nature of the excitonic state. Furthermore we address the question of a multiconfigurational ground state in monolayer black phosphorus. [1] A. N. Rudenko, Shengjun Yuan, and M. I. Katsnelson, Phys. Rev. B 92 085419 (2015) [Preview Abstract] |
Tuesday, March 15, 2016 12:27PM - 12:39PM |
F15.00007: Prediction of two-dimensional van der Waals ferroelectric materials Wenjun Ding, Jianbao Zhu, Yanfei Gao, Di Xiao, Yi Gu, Zhenyu Zhang, Wenguang Zhu Based on density functional theory calculations, we discover a class of two-dimensional van der Waals ferroelectric materials with spontaneous out-of-plane electric polarization, and the orientation of the electric polarization can be reversed by a seemly lateral shift of a single atomic layer. We further find that the electronic structures of a bilayer of such two-dimensional ferroelectric materials can be switched to be either semiconducting or metallic, depending on their relative orientations of the electric polarization. This finding expand the family of the two-dimensional materials with ferroelectricity and offers new opportunities to tune the properties of van der Waals heterstructures for practical device applications. [Preview Abstract] |
Tuesday, March 15, 2016 12:39PM - 12:51PM |
F15.00008: Giant piezoelectricity of monolayer group IV monochalcogenides. Ruixiang Fei, Wenbin Li, Ju Li, Li Yang We predict enormous, anisotropic piezoelectric effects in intrinsic monolayer group IV monochalcogenides (MX, M$=$Sn or Ge, X$=$Se or S), including SnSe, SnS, GeSe, and GeS. Using first-principle simulations based on the modern theory of polarization, we find that their piezoelectric coefficients are about one to two orders of magnitude larger than those of other 2D materials, such as MoS2 and GaSe, and bulk quartz and AlN which are widely used in industry. This enhancement is a result of the unique ``puckered'' C2v symmetry and electronic structure of monolayer group IV monochalcogenides. Given the achieved experimental advances in the fabrication of monolayers, their flexible character, and ability to withstand enormous strain, these 2D structures with giant piezoelectric effects may be promising for a broad range of applications such as nano-sized sensors, piezotronics, and energy harvesting in portable electronic devices. [Preview Abstract] |
Tuesday, March 15, 2016 12:51PM - 1:03PM |
F15.00009: ABSTRACT WITHDRAWN |
Tuesday, March 15, 2016 1:03PM - 1:15PM |
F15.00010: Structural variability and electronic properties of bulk and monolayer Si2Te3 Corey Combs, Xiao Shen, Yevgeniy Puzyrev, Lida Pan, Sokrates Pantelides Silicon telluride, a layered material recently experimentally made to a few atomic layer-thick (1) has intriguing variations of optical and electronic properties, associated with the flexibility of its structure. In Si2Te3, the Te atoms form a hexagonal close packed structure, while Si atoms form Si-Si dimers and fill 2/3 of the allowed sites. There are 4 possible orientations of the Si-Si dimers, 3 in-plane directions 60 degrees to each other and one out-of-plane direction perpendicular to 2D plane. X-ray and electron diffraction data on bulk Si2Te3 suggested that 1/4 of the dimers are vertical while the other 3/4 of the dimers are randomly oriented horizontally. We performed density functional calculations to show that both bulk and monolayer Si2Te3 exhibit large variations in properties, resulting from reorientation of silicon dimers. These variations are up to 5 percent in lattice constant and up to 40 percent in electron band gap. Transition of Si2Te3 from bulk to monolayer configuration also shows an increase in the band gap and lattice constant. We show that these properties are, in principle, controllable by temperature and strain, making Si2T3 a promising candidate as optomechanical and optoelectronic material. (1) Keuleyan, S. et al. Nano Lett. 2015, 15 (4), 2285-2290. [Preview Abstract] |
Tuesday, March 15, 2016 1:15PM - 1:27PM |
F15.00011: Effect of functionalization on the electronic and atomic properties of layered MXenes Kurt Fredrickson, Aleksandra Vojvodic, Jens Nørskov MXenes (M $=$ Transition Metal, X $=$ C or N) are a promising family of materials that have been recently manufactured from MAX phases. MXenes have already been shown as promising candidates for use in lithium ion batteries, supercapacitors, and fuel cells (1). MXenes consist of M\textunderscore (x)X\textunderscore (x-1), two-dimensional sheets weakly bound by van der Waals forces. However, due to the selective removal of the A ion to manufacture MXenes, they are highly reactive, with a wide variety of possible functional groups. Previous studies have shown that the electronic properties of MXene single sheets are highly dependent on their functionalization, but so far there are few studies on the effect of functionalization of the bulk phase of MXene, which consists of many layers of MXenes bound together. In this talk, we will illustrate the effect of functionalization of bulk MXenes by H, H$_{\mathrm{2}}$, OH, and O for Mo$_{\mathrm{2}}$C and Ti$_{\mathrm{2}}$C. We will also show the effect of applied potential on the functionalization of Mo$_{\mathrm{2}}$C and Ti$_{\mathrm{2}}$C. Finally, we will compare our results with experimental measurements. (1) M. Naguib, V.D. Mochalin, M.W. Barsoum and Y. Gogotsi, \textit{Adv. Mater.} \textbf{26}, 992 (2014). [Preview Abstract] |
Tuesday, March 15, 2016 1:27PM - 1:39PM |
F15.00012: Single layer lead iodide: computational exploration of structural, electronic and optical properties, strain induced band modulation and the role of spin--orbital-coupling Mei Zhou, Wenhui Duan, Ying Chen, Aijun Du Graphitic like layered materials exhibit intriguing electronic structures and the search for new types of two-dimensional (2D) monolayer materials is of great interest for developing novel nano-devices. By using density functional theory method, we investigate the structure, stability, electronic and optical properties of monolayer lead iodide (PbI$_{\mathrm{2}})$. The stability of PbI$_{\mathrm{2}}$ monolayer is first confirmed by phonon dispersion calculation. Compared to the calculation using generalized gradient approximation, screened hybrid functional and spin--orbit coupling effects can predicts an accurate band gap (2.63 eV). The biaxial strain can tune its band gap size in a wide range from 1 eV to 3 eV, which can be understood by the strain induced uniformly change of electric field between Pb and I atomic layer. The calculated imaginary part of the dielectric function of 2D graphene/PbI$_{\mathrm{2}}$ van der Waals type hetero-structure shows significant red shift of absorption edge compared to that of a pure monolayer PbI$_{\mathrm{2}}$. Our findings highlight a new interesting 2D material with potential applications in nanoelectronics and optoelectronics. [Preview Abstract] |
Tuesday, March 15, 2016 1:39PM - 1:51PM |
F15.00013: Two-dimensional silicon and carbon monochalcogenides with the structure of phosphorene Dario Rocca, Ali Abboud, S\'ebastien Leb\`egue, Ganapathy Vaitheeswaran Phosphorene has recently attracted interest for applications in transistors and photodetectors. Inspired by this material we carried out an ab initio study to predict new binary materials with a structure similar to phosphorene. Specifically, carbon or silicon atoms and chalcogen atoms (up to Te) were combined to form a phosphorene-like monolayer. The structure of these new compounds was then optimized and the dynamical stability of the structures was demonstrated by computing phonon dispersion curves. A series of materials were found to be stable: CS, CSe, CTe, SiO, SiS, SiSe, and SiTe. Electronic properties such as band gaps and effective masses were computed at the density functional theory level. By using the accurate HSE hybrid functional it was found that these materials span a broad range of bandgaps, going from the 2.1 eV of SiS to the 0.55 eV of SiTe. The effective masses were also computed; similarly to phosphorene, a strong anisotropy was found when comparing the zigzag and armchair directions. The variety of electronic properties found for these systems will contribute to broaden the technological applicability of two dimensional materials. [Preview Abstract] |
Tuesday, March 15, 2016 1:51PM - 2:03PM |
F15.00014: Electron counting and a large family of two-dimensional semiconductors Maosheng Miao, Jorge Botana, Eva Zurek, Jingyao Liu, Wen Yang Two-dimensional semiconductors (2DSC) are currently the focus of many studies, thanks to their novel and superior transport properties that may greatly influence future electronic devices. The potential applications of 2DSCs range from low-dimensional electronics, topological insulators and vallytronics all the way to novel photolysis. However, compared with the conventional semiconductors that are comprised of main group elements and cover a large range of band gaps and lattice constants, the choice of 2D materials is very limited. In this work, we propose and demonstrate a large family of 2DSCs, all adopting the same structure and consisting of only main group elements. Using advanced density functional calculations, we demonstrate the attainability of these materials, and show that they cover a large range of lattice constants, band gaps and band edge states, making them good candidate materials for heterojunctions. This family of two dimensional materials may be instrumental in the fabrication of 2DSC devices that may rival the currently employed 3D semiconductors. [Preview Abstract] |
Tuesday, March 15, 2016 2:03PM - 2:15PM |
F15.00015: Highly anisotropic Dirac fermions in square graphynes Lizhi Zhang, Zhengfei Wang, Jiansheng Rao, Ziheng Li, Wulin Huang, Zhiming Wang, Shixuan Du, Hongjun Gao, Feng Liu Recently, there have been intense search of new 2D materials, and one especially appealing class of 2D materials is the all-carbon allotropes of Dirac materials. Here, we predict a new family of 2D carbon allotropes, square graphynes (S-graphynes) that exhibit highly anisotropic Dirac Fermions, using first-principle calculations within density functional theory. The equal-energy contour of their 3D band structure shows a crescent shape, and the Dirac crescent has varying Fermi velocities from 0.6 \texttimes 10$^{\mathrm{5}}$ to 7.2 \texttimes 10$^{\mathrm{5}}$ m/s along different k directions. Near the Fermi level, the Dirac crescent can be nicely expressed by an extended 2D Dirac model Hamiltonian. Furthermore, tight-binding band fitting reveals that the Dirac crescent originates from the next-nearest-neighbor interactions between C atoms. Our findings enrich the Dirac physics founded in other 2D Dirac systems, and offer a new design mechanism for creating Dirac band by tuning the interaction range. We envision that the highly anisotropic Dirac crescent may be exploited in all-carbon-based electronic devices for manipulating anisotropic electron propagation. [Preview Abstract] |
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