Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session C27: Electronic Structure 
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Sponsoring Units: FIAP Chair: Murali Kota, GlobalFoundries Room: 290 
Monday, March 13, 2017 2:30PM  2:42PM 
C27.00001: Effects of Metal Orientation and Alloying on MetalSemiconductor Schottky Barriers Eduardo C. Silva, Domingo A. Ferrer, J. Israel Ramirez, Praneet Adusumilli, Oscar D. Restrepo, Rinus Lee, Wonwoo Kim, Murali Kota The electric resistance of metalsemiconductor (MS) junctions is one of the limiting factors in the aggressive scaling of sub14 nm semiconductor devices including nanowire field effect transistors (FETs) and FinFETs. The Schottky barrier caused by the charge transfer at MS juntion is the root cause of this interface resistance, which in turn limits the power and performance of semiconductor nanodevices. In this study, we employ density functional theory and a generalized transfer matrix method to study the electronic structure and transport properties of Titanium Silicide / Silicon junctions, as well as the effects of metal orientation and alloying on the metalsemiconductor Schottky barrier for both p and ntype semiconductor devices. We will comment on the possible ways to effectively modulate the Schottky barriers in order to meet the MS junction resistance targets needed to enable sub14nm semiconductor technologies. [Preview Abstract] 
Monday, March 13, 2017 2:42PM  2:54PM 
C27.00002: TimeDependent Molecular Response with both Electric and Magnetic Fields Rachel Glenn, Andrew James, T. Daniel Crawford Timedependent molecular simulations of optical spectroscopy conventionally consider the electric field strength much stronger than the magnetic strength. The various molecular dynamics contributing to a optical spectrum of a molecule in solution are timedependent, some occur in the early time response (rotationaldegrees) and some on a longer time response (translationaldegrees) of the molecule. This has motivated us to develop timedependent molecular response theory with both the magnetic and electric fields included. Here, I will discuss the our movement towards timedependent quantum chemistry, and our recent results with the optical activity of chiral molecules. [Preview Abstract] 
Monday, March 13, 2017 2:54PM  3:06PM 
C27.00003: Correct implementation of polarization constants in wurtzite materials and impact on IIInitrides Cyrus E. Dreyer, Anderson Janotti, Chris G. Van de Walle, David Vanderbilt Accurate values for polarization discontinuities between pyroelectric materials are critical for understanding and designing the electronic properties of heterostructures. For wurtzite materials, the zincblende structure has been used in the literature as a reference to determine the effective spontaneous polarization constants. We show that, because the zincblende structure has a nonzero formal polarization, this method results in a spurious contribution to the spontaneous polarization differences between materials. In addition, we address the correct choice of “improper” versus “proper” piezoelectric constants. For the technologically important IIInitride materials GaN, AlN, and InN, we determine polarization discontinuities using a consistent reference based on the layered hexagonal structure and the correct choice of piezoelectric constants, \footnote{C. E. Dreyer, A. Janotti, C. G. Van de Walle, and D. Vanderbilt, Phys. Rev. X \textbf{6}, 021038 (2016)} and discuss the results in light of available experimental data. [Preview Abstract] 
Monday, March 13, 2017 3:06PM  3:18PM 
C27.00004: Electronic band structures and phonons in CdIVN$_2$ semiconductors Sai Lyu, Walter Lambrecht Heterovalent ternary semiconductors of formula IIIVN$_2$ have recently attracted some interest to complement the group IIIN nitride semiconductors. Here we study the CdIVN$_2$ materials with IV=Si,Ge,Sn. Their electronic band structures are calculated in quasiparticle selfconsistent GW approximation and fullpotential linearized muffintin orbital approach. The lattice parameters are calculated with the local density approximation (LDA) and generalized gradient approximation(GGA). We also computed the effective masses of the valence bands and the conduction bands. The symmetry labels of the bands near the Fermi level were determined. The CdSiN$_2$ and CdGeN$_2$ are found to be indirect band gap semiconductors, while CdSnN$_2$is found to be direct band gap semiconductors.The gaps range from deep ultraviolet to shallow infrared.The phonon frequencies at the Brillouin zone center and Raman spectra are also calculated using density functional perturbation theory. The Born effective charges and dielectric constants are also reported. [Preview Abstract] 
(Author Not Attending)

C27.00005: Energetics of the spinstate transition in LaCoO3: Total energy calculations using DFT$+$DMFT Ravindra Nanguneri, Hyowon Park In this talk, we will present the energetics of the spinstate transition in strongly correlated LaCoO3 by adopting total energy calculations within density functional theory plus dynamical mean field theory (DFT$+$DMFT). We computed total energy curves as a function of volume for different spin states including low spin (LS), high spin (HS), and 1:1 mixed HSLS states. We will show that as the volume is expanded, the mixed HSLS state becomes energetically stable with a reasonable energy gap to the groundstate LS state. The nature of the HSLS state is a paramagnetic insulator consistent with experiment while the homogeneous HS state is energetically much higher compared to the LS state. To analyze the dynamical fluctuation effect on the energetics, we also computed DFT$+$U energy curves by adopting the maximally localized Wannier function as correlated orbitals, same as used in DFT$+$DMFT calculations. The static correlation effect treated in DFT$+$U overestimates the tendency to higher spin states and the mixed spin state is wrongly predicted to be the ground state. The effect of the Coulomb interaction U, the Hund's coupling J, and the double counting potential on the energetics will be also discussed. [Preview Abstract] 
Monday, March 13, 2017 3:30PM  3:42PM 
C27.00006: Abinitio Computation of the Electronic, transport, and Bulk Properties of Calcium Oxide. Augustine Mbolle, Dipendra Banjara, Yuriy Malozovsky, Lashounda Franklin, Diola Bagayoko We report results from abinitio, selfconsistent, local Density approximation (LDA) calculations of electronic and related properties of calcium oxide (CaO) in the rock salt structure. We employed the Ceperley and Alder LDA potential and the linear combination of atomic orbitals (LCAO) formalism. Our calculations are nonrelativistic. We implemented the LCAO formalism following the Bagayoko, Zhao, and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZWEF). The BZWEF method involves a methodical search for the optimal basis set that yields the absolute minima of the occupied energies, as required by density functional theory (DFT). Our calculated, indirect band gap of 6.91eV, from Ã towards the L point, is in excellent agreement with experimental value of 6.937.7eV, at room temperature (RT). We have also calculated the total (DOS) and partial (pDOS) densities of states as well as the bulk modulus. Our calculated bulk modulus is in excellent agreement with experiment. [Preview Abstract] 
Monday, March 13, 2017 3:42PM  3:54PM 
C27.00007: Firstprinciples studies of electronic, transport and bulk properties of pyrite FeS}$_{\mathrm{\mathbf{2}}}$ Dipendra Banjara, Augustine Mbolle, Yuriy Malozovsky, Lashounda Franklin, Diola Bagayoko We present results of abinitio, selfconsistent density functional theory (DFT) calculations of electronic, transport, and bulk properties of pyrite FeS$_{\mathrm{2}}$. We employed a local density approximation (LDA) potential and the linear combination of atomic orbitals (LCAO) formalism, following the Bagayoko, Zhao and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZWEF). The BZWEF method requires successive, self consistent calculations with increasing basis sets to reach the ground state of the system under study. We report the band structure, the band gap, total and partial densities of states, effective masses, and the bulk modulus. [Preview Abstract] 
Monday, March 13, 2017 3:54PM  4:06PM 
C27.00008: Accurate Electronic, transport, and Related Properties of Wurtzite Beryllium Oxide (wBeO) Cheick Bamba, Richard Inakpenu, Yacouba Diakite, Yuriy Malozovsky, Lashounda Franklin, Diola Bagayoko We present abinitio, selfconsistent density functional theory (DFT) description of electronic and related properties of wurtzite beryllium oxide (wBeO). We used a local density approximation (LDA) potential and the linear combination of atomic orbitals (LCAO) formalism. Our implementation of the Bagayoko, Zhao, and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZWEF), ensures the full, physical content of the results of our calculations [AIP advances, 4, 127104 (2014). We report the band gap, the total and partial densities of states, and effective masses. Our calculated, direct band gap of 10.29 eV, using experimental lattice constants of a $=$ 2.6979 and c $=$ 4.3772 at room temperature, agrees with some experimental ones of 10.3 eV and not with others (7.8, 8.8, 9.6 10.45, and 10.6 eV). [Preview Abstract] 
Monday, March 13, 2017 4:06PM  4:18PM 
C27.00009: Abinitio Computations Of Electronic, Transport, And Structural Properties Of Zinc Blende Beryllium Selenide (Zbbese). Richard Inakpenu, Cheick Bamba, Ifeanyi Nwigboji, Lashounda Franklin, Yuriy Malozovsky, GuangLin Zhao, Diola Bagayoko We report results from several abinitio, selfconsistent computations of electronic, transport and bulk properties of \textit{zinc blende }beryllium selenide (\textit{zb}BeSe). Our non relativistic calculations utilized a local density approximation (LDA) potential and the linear combination of atomic orbitals (LCAO). The key distinction of our calculations from other DFT ones is our implementation of the Bagayoko, Zhao and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZWEF). Our calculated, indirect band gap is 5.46 eV, from Ã to a conduction band minimum between Ã and X, for a room temperature lattice constant of 5.152 {\AA}. Available, room temperature experimental band gaps of 5.5 eV (direct) and 4.0  4.5 eV (unspecified) point to the need for additional measurements. Our calculated bulk modulus of 92.35 GPa is in excellent agreement with experiment (92.2 $\pm$ 1.8 GPa). Our predicted equilibrium lattice constant and band gap, at zero temperature, are 5.0438 {\AA} and 5.4 eV, respectively. [Preview Abstract] 
Monday, March 13, 2017 4:18PM  4:30PM 
C27.00010: Sulfuralloyed chromium oxide: A new ptype transparent conducting oxide host Samira Dabaghmanesh, Roland Saniz, Erik Neyts, Bart Partoens Developing a ptype transparent conducting oxide (TCO) has always been challenging. The main problem of most ptype TCOs is the high effective hole mass, resulting in a low conductivity, brought by a flat valence band. In our work, we introduce sulfuralloyed Cr$_2$O$_3$ as a new TCO host. Using firstprinciples methods we investigate whether we can increase the valence band dispersion (i.e. reduce the hole mass) by anion alloying with sulfur, while keeping the band gap large enough for optical transparency. We calculate the electronic properties of Cr$_4$S$_x$O$_{6x}$ and consider different alloying concentrations x=15. We critically examine the accuracy of different density functionals and methods, including PBE, PBE+U, HSE06, as well as perturbative approaches within the GW approximation. Our results demonstrate that Cr$_4$S$_2$O$_4$ has an optical band gap of 3.08 eV and an effective hole mass of 1.8 m$_e$. This suggests Cr$_4$S$_2$O$_4$ as a new ptype TCO host candidate. [Preview Abstract] 
Monday, March 13, 2017 4:30PM  4:42PM 
C27.00011: Possible electric field induced indirect to direct band gap transition in MoSe$_{\mathrm{2}}$ Beom Seo Kim, Wonshik Kyung, Jeongjin Seo, Junyoung Kwon, Changyoung Kim, Seung Ryong Park Novel phenomena such as indirect to direct band gap transition, spinvalleylayer locking and polarization dependent valley control are attractive features of transition metal dichalcogenides (TMDs). Here, we report the possibility for electric field induced indirect to direct band gap transition in bulk MoSe$_{\mathrm{2}}$ observed by using angle resolved photoemission spectroscopy (ARPES). In order to demonstrate the evolution of the electronic structure as a function of surface electron doping and/or surface electric field, we use \textit{insitu} alkali metal dosing on the surface of \textit{insitu} cleaved MoSe$_{\mathrm{2}}$. We find that the alkali metal evaporation affects the $\Gamma $ and the K point electronic structure differently. The difference in binding energy between valence band maximum (VBM) at the $\Gamma $ and the K points changes from 370 meV to 30 meV. Our results not only clearly show a possibility of indirect to direct band gap transition by electric field, but also show the relation between the gap size and surface electric field in semiconductor. [Preview Abstract] 
Monday, March 13, 2017 4:42PM  4:54PM 
C27.00012: Resonant Inelastic Xray Scattering of Hexagonal Boron Nitride John Vinson, Terrence Jach, Matthias Mueller, Rainer Unterumsberger, Burkhard Beckhoff We present resonant xray emission spectra, both measured and calculated, at the nitrogen edge of hexagonal boron nitride. Using the BetheSalpeter equation as implemented in the {\sc ocean} code, we investigate the effects of {\it GW} selfenergy corrections and atomic disorder on the spectra. We highlight the importance of considering the effects of the corehole excitation on the vibrational state of the system, and point to ways to include such effects in calculations of extended systems. [Preview Abstract] 
Monday, March 13, 2017 4:54PM  5:06PM 
C27.00013: Compact localized states and flatband generators in one dimension Wulayimu Maimaiti, Alexei Andreanov, Hee Chul Park, Oleg Gendelman, Sergej Flach Flat bands (FB) are strictly dispersionless bands in the Bloch spectrum of a periodic lattice Hamiltonian, recently observed in a variety of photonic and dissipative condensate networks. We classify FB networks through the properties of compact localized states (CLS) which are exact FB eigenstates and occupy $U$ unit cells. We obtain necessary and sufficient conditions for a network to be of FB class $U$. These conditions are turned into a simple local FB testing routine which avoids Bloch based band structure calculations. The tester in turn is used to introduce a novel FB generator based on local algebraic network properties. We obtain the complete FB family of twoband networks in one dimension with nearest unit cell interaction, for which $U \leq 2$. We find that the CLS set is generically linearly independent and spans the complete FB Hilbert space. With the CLS structure we obtain the Bloch polarization vectors of the FB. [Preview Abstract] 
Monday, March 13, 2017 5:06PM  5:18PM 
C27.00014: Direct observation of nonequivalent valley in WSe$_{2}$ by ARPES with circularly polarized light. Soohyun Cho, Garam Han, Jonkwen Jung, JinHong Park, Seung Ryong Park, Changyoung Kim Monolayer WSe$_{2}$ has spin band splitting at K point and nonequivalent valley which make it a good candidate for several applications such as valleytronic devices. Topological transport phenomena induced by valley Hall effect is supported by Berry's phase. Recently theoretical predictions indicated that Bloch electrons of monolayer WSe2 with broken inversion symmetry carry opposite sign of Berry's curvature between K and K valley. It was recently reported that nontrivial Berry's phase of graphene was shown by Circular Dichroism pattern (CDpattern) via ARPES with circular polarized light. To investigate Berry' curvature of WSe2, We performed CDARPES on 2H bulk WSe$_{2\, }$from the K(K) to K(K) point. Even though 2H bulk WSe$_{2}$ was measured on CDpattern, its CDpattern was analogous to monolayer WSe$_{2}$ because of short probing depth. We aruge that our results display on CDpattern proportional to Berry's curvature in the momentum space and have anitsymmetry behavior with respect to gamma M line. [Preview Abstract] 
Monday, March 13, 2017 5:18PM  5:30PM 
C27.00015: Quantum scars in quantum dots Esa Rasanen, Joonas KeskiRahkonen, Perttu Luukko, Lev Kaplan, Eric Heller A quantum scar [1] corresponds to enhanced density along an unstable classical periodic orbit. Recently, it was shown that twodimensional (2D) separable quantum systems perturbed by randomly distributed bumps show a new type of scarring, which is unexpectedly strong and robust [2]. These scars follow the classical orbits of the corresponding unperturbed system (without bumps). In this work we show that 2D harmonic oscillators  common models for semiconductor quantum dots  exhibit strong quantum scarring under a perpendicular magnetic field and perturbation in the potential. Moreover, both the geometry of the scar (line, triangular, square, etc.) and its orientation can be controlled even by a single bump in the potential. Thus, the scheme allows us to use local voltage gates to control quantum conductance along strongly scarred states in semiconductor quantum dots. [1] E. J. Heller, Phys. Rev. Lett. 53, 1515 (1984); [2] P. J. J. Luukko, A. Klales, B. Drury, L. Kaplan, E. J. Heller, and E. Rasanen, Sci. Rep. (in print, 2016). [Preview Abstract] 
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