Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session C20: Firstprinciples Modeling of Excitedstate Phenomena in Materials III: Recent Advances in Excited State FormalismsFocus

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Sponsoring Units: DCOMP DMP Chair: Felipe Da Jornada, Lawrence Berkeley National Laboratory Room: BCEC 157A 
Monday, March 4, 2019 2:30PM  3:06PM 
C20.00001: Electronic and optical excitations from screened rangeseparated hybrid density functional theory Invited Speaker: Leeor Kronik Some ten years ago, we have introduced the concept of optimal tuning (OT) of rangeseparated hybrid (RSH) functionals as a means of overcoming the fundamental gap problem and the charge transfer excitation problem in molecular systems. Here, this concept is extended to the solid state by introducing dielectric screening into the functional form. This approach, couched rigorously within the generalized KohnSham formalism of density functional theory, can produce quantitatively the same one and two quasiparticle excitation picture given by manybody perturbation theory. Specifically, for molecular solids the approach predicts the correct gap renormalization without any empiricism. This can be achieved even from single molecule calculations if a polarizable continuum model is combined with the screened OTRSH calculation in an electrostatically consistent manner. For covalent/ionic semiconductors and insulators, one empirical parameter is set to reproduce the direct bandgap. Accurate band structures and optical absorption spectra, which agree well with those obtained from GW and GWBSE calculations, respectively, are then obtained. 
Monday, March 4, 2019 3:06PM  3:18PM 
C20.00002: Screened RangeSeparated Hybrid Functional and GW + GWBSE Calculations of Prototypical Semiconductors: A Comparison Dahvyd Wing, Jonah Haber, Roy Noff, Bradford Barker, David Egger, Ashwin Ramasubramaniam, Steven G. Louie, Jeffrey B Neaton, Leeor Kronik We present band structure and optical absorption spectra obtained from a screened rangeseparated hybrid (SRSH) functional, including spinorbit coupling, for seven prototypical semiconductors. The results are compared to those obtained from highly converged many body perturbation theory calculations using the GW approximation and the GW plus BetheSalpeter equation (GWBSE) approaches. We use a single empirical parameter, fit such that the SRSH band gap reproduces the GW band gap at the Γ point. We then find that groundstate generalized KohnSham SRSH eigenvalues accurately reproduce the band structure obtained from GW calculations, and optical absorption spectra obtained using linearresponse timedependent DFT with the SRSH functional agree well with those of GWBSE, at a fraction of the computational cost. 
Monday, March 4, 2019 3:18PM  3:30PM 
C20.00003: Transferable screened rangeseparated hybrids for layered materials Ashwin Ramasubramaniam, Dahvyd Wing, Leeor Kronik The optoelectronic properties of layered semiconductors can vary significantly between bulk (3D) phases and their single or fewlayer, 2D counterparts. In particular, the vastly different asymptotic behavior of dielectric screening in 2D and 3D structures poses a challenge for designing screened rangeseparated hybrid (SRSH) functionals that are accurate for both bulk and lowdimensional systems. We present a simple yet effective approach for simultaneously tuning the fraction of shortrange exact exchange and the rangeseparation parameter that delivers tuned SRSH functionals for 2D sheets and 3D bulk phases of layered semiconductors. The groundstate SRSH eigenvalues are found to be in excellent agreement with bandstructures from accurate, manybody GW calculations. Excited state properties are predicted using timedependent DFT calculations, based on the SRSH functional, and are also found to be in good agreement with absorption spectra obtained from GW and BetheSalpeter (BSE) calculations. The ability to develop SRSH functionals that are only material but not structurespecific opens up avenues for systematic and accurate studies of layered materials and their nanostructures at a fraction of the cost of manybody calculations. 
Monday, March 4, 2019 3:30PM  3:42PM 
C20.00004: Firstprinciples study of bioinspired perylene diimide molecular nanowires Aliya Mukazhanova, Nathan Frey, Kasidet Trerayapiwat, Amir Mazaheripour, Andrew Bartlett, Hung Nguyen, Alon A. Gorodetsky, Sahar Sharifzadeh Perylene3,4,9,10tetracarboxylic diimide (PTCDI) has excellent electrochemical and photophysical properties that makes it a promising material for optoelectronic devices. Molecular nanowires consisted from PTCDI derivatives can be placed in DNA like base by standard automated oligonucleotide synthesis. Here, we study the electronic and optical properties of a series of recently synthesized bioinspired perylene diimide molecular nanowires by firstprinciples density functional theory (DFT) spectroscopy and molecular dynamics (MD). We apply timedependent DFT with FranckCondon analysis to study our material. Initial structures are taken from MD and the final vibronic spectra is an average over many structures. By stacking the molecules along a DNAlike backbone and varying the number of stacked molecules from one to four, we determine the role of intermolecular interactions on the excitedstate energetics, as well as vibrational excitations within the molecules. We demonstrate that strong intermolecular interactions lead to distinct vibrational, electronic, and optical properties for design of new electronic and optoelectronic nanowires. 
Monday, March 4, 2019 3:42PM  3:54PM 
C20.00005: Phase stability of MnSe, MnTe, and VO_{2} from total energies in the random phase approximation Stephan Lany While the limitations (semi)local density functionals for the electronic structure are widely acknowledged, total energies are usually considered to be rather accurate. However, in transition metal compounds, standard density or even hybrid functionals often predict the wrong ground state structure. Total energy calculations in the random phase approximation (RPA) greatly improve the phase stability prediction, e.g., rocksalt vs wurtzite in MnO, but quantitative predictions are still sensitive on input wavefunction for the RPA energy [1]. Here, we calculate the phase stability for MnSe and MnTe in the rocksalt, nickeline, and wurtzite structures, for the "negativepressure" phase in MnSeTe alloys [2]. To account for the wavefunction dependence, we perform a variational minimization of the RPA energy with respect to the onsite potentials U and V [1]. In VO2, the failure of standard DFT to produce a band gap can be remedied by simple DFT+U calculation, at the expense of the incorrect prediction that the undistorted antiferromagnetic phase is lower in energy than the experimentally known nonmagnetic monoclinic phase. We further discuss results based on the SCAN functional. 
Monday, March 4, 2019 3:54PM  4:06PM 
C20.00006: Can exact (local) KohnSham potential reproduce band gaps?: Analysis using an analytically solvable two and threebody models Yuichiro Matsushita, Taichi Kosugi We have clarified whether the exact (local) KohnSham(KS) potential reproduces the exact band gap or not [1]. We have investigated the analytically solvable interacting two and threebody models and calculated the exact electron levels through the oneparticle Green's function of the twobody system analytically. Subsequently, we constructed the exact KS potential analytically and compared the obtained KS levels with exact ones. Then, we have found that KSDFT even with the exact (local) KS potential does not reproduce the exact band gaps. 
Monday, March 4, 2019 4:06PM  4:18PM 
C20.00007: Wannier Koopmans method for band gap calculations of extended systems LinWang Wang, Mouyi Weng, Feng Pan We have developed a method to correct the density functional theory band gap problem, especially for extended systems. In this method, the Wannier functions are generated and the Hamiltonian is required to satisfy the Koopman theory (the total energy is linearly dependent on the occuption number) when a Wannier function is partially occupied. The resulting Hamiltonian gives a correction term for the KohnSham eigen equation. This method can be considered as an extention of the delta DFT method to bulk systems. We have used this method to study common semiconductors, alkali halides, 2D materials, organic crystals, as well as oxides. We found in general, the accuracy of this Wannier Koopman method (WKM) is on a par with the GW results. 
Monday, March 4, 2019 4:18PM  4:30PM 
C20.00008: WITHDRAWN ABSTRACT

Monday, March 4, 2019 4:30PM  4:42PM 
C20.00009: HighHarmonic Gereration with quantized fields: Minimal coupling of Pauli Spinors to quantized electromagnetic fields MaryLeena Martine Tchenkoue Djouom, Davis Dave Welakuh, Michael Ruggenthaler, Heiko Appel, Angel Rubio

Monday, March 4, 2019 4:42PM  4:54PM 
C20.00010: Polaritonic chemistry: The influence of mass renormalization Davis Dave Welakuh, MaryLeena Martine Tchenkoue Djouom, Michael Ruggenthaler, Heiko Appel, Angel Rubio If molecules are placed inside a cavity or near a plasmonic surface strong lightmatter interaction can occur that mixes matter and photon degrees of freedom [1]. This can modify properties of molecules [2] and can even alter chemical reactions due to the changed electromagentic vacuum. The theoretical descriptions of such novel chemical situations is usually done with simplified fewlevel models and only recently more advanced abinitio methods [4] have been developed and applied [5]. However, so far all these considerations have negelected the influence of the changed electromagentic vacuum on the masses of the particles. That is, while the mass of electrons and nuclei are usually defined with respect to the bare electromagnetic vacuum, in the above cases the electromagentic vacuum is changed considerably. Here we present first abinitio studies of how multimode fields influence the total mass of the particles and thus change physical obervables. 
Monday, March 4, 2019 4:54PM  5:06PM 
C20.00011: First principles approaches to strong lightmatter coupling Johannes Flick, Prineha Narang In recent years, research at the interface of chemistry, material science, and quantum optics has surged, now opens new possibilities to study strong lightmatter interactions at different limits [1,2]. In this new regime, correlated electron, nuclear and photon interactions have to be treated on the same quantized footing [3] and towards this overarching goal, we have introduced a general timedependent densityfunctional theory. 
Monday, March 4, 2019 5:06PM  5:18PM 
C20.00012: Time evolution methods for matrixproduct states Sebastian Paeckel, Andreas Swoboda, Thomas Koehler, Salvatore Manmana, Ulrich Joseph Schollwoeck, Claudius Hubig Matrixproduct states (MPS) have become the de facto standard for the investigation of onedimensional quantum many body systems, also outofequilibrium. 
Monday, March 4, 2019 5:18PM  5:30PM 
C20.00013: Calculating Quantum Corrections to Electronic Transport in Disordered Nanostructures Chenyi Zhou, Hong Guo Electronic transport in nanostructures shows strong dependencies on disorder and related quantum effects. The leadingorder quantum corrections to the diffusive transport were identified as the weaklocalization (WL) and the AltshulerAronov (AA) effects. An important issue is to develop a numerical method for computing these quantum corrections starting from the atomistic arrangement. To this end, a diagrammatic scheme based on nonequilibrium Green functions is put forward. We employ a nonlocal expansion technique to generate Cooperon diagrams in oder to capture WL. We implement this approach using a tightbinding Anderson model to simulate finite wires containing disorder. In WL regime, our computed conductance agrees well with the exact numerical solution, and the WL corrected resistance shows a nonlinear scaling versus the channel length. The WL induced negative magnetoresistance is also investigated. For AA correction, we extend the numerical GW method by dressing interaction vertices with diffusons, and we apply it to a finite AndersonHubbard model. Density of states anomalies are found at energies corresponding to bias voltages, and their size dependence is analyzed. The AA effect in nonlinear transport will also be reported. 
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