scholarly journals Cooperative evolution of polar distortion and nonpolar rotation of oxygen octahedra in oxide heterostructures

2021 ◽  
Vol 7 (17) ◽  
pp. eabe9053
Author(s):  
Taewon Min ◽  
Wooseon Choi ◽  
Jinsol Seo ◽  
Gyeongtak Han ◽  
Kyung Song ◽  
...  
Keyword(s):  
Density Functional ◽  
Direct Evidence ◽  
Misfit Strain ◽  
Strongly Correlated ◽  
Functional Theory ◽  
Oxide Heterostructures ◽  
Cooperative Evolution ◽  
Structural Distortions ◽  
Dimensional Electron Gas ◽  
Electron Energy Loss

Polarity discontinuity across LaAlO3/SrTiO3 (LAO/STO) heterostructures induces electronic reconstruction involving the formation of two-dimensional electron gas (2DEG) and structural distortions characterized by antiferrodistortive (AFD) rotation and ferroelectric (FE) distortion. We show that AFD and FE modes are cooperatively coupled in LAO/STO (111) heterostructures; they coexist below the critical thickness (tc) and disappear simultaneously above tc with the formation of 2DEG. Electron energy-loss spectroscopy and density functional theory (DFT) calculations provide direct evidence of oxygen vacancy (VO) formation at the LAO (111) surface, which acts as the source of 2DEG. Tracing the AFD rotation and FE distortion of LAO reveals that their evolution is strongly correlated with VO distribution. The present study demonstrates that AFD and FE modes in oxide heterostructures emerge as a consequence of interplay between misfit strain and polar field, and further that their combination can be tuned to competitive or cooperative coupling by changing the interface orientation.

A flat-lying dimer as a key intermediate in NO reduction on Cu(100)

2021 ◽  
Author(s):  
Kenta Kuroishi ◽  
Muhammad Rifqi Al Fauzan ◽  
Ngoc Thanh Pham ◽  
Yuelin Wang ◽  
Yuji Hamamoto ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Density Functional Theory ◽  
Scanning Tunneling Microscope ◽  
Density Functional ◽  
No Reduction ◽  
Density Functional Theory Calculations ◽  
Scanning Tunneling ◽  
Functional Theory ◽  
Tunneling Microscope ◽  
Electron Energy Loss

The reaction of nitric oxide (NO) on Cu(100) is studied by scanning tunneling microscope, electron energy loss spectroscopy and density functional theory calculations. The NO molecules adsorb mainly as monomers...

scholarly journals Predicting the conductance of strongly correlated molecules: the Kondo effect in perchlorotriphenylmethyl/Au junctions

Nanoscale ◽  
2018 ◽  
Vol 10 (37) ◽  
pp. 17738-17750 ◽  
Author(s):  
W. H. Appelt ◽  
A. Droghetti ◽  
L. Chioncel ◽  
M. M. Radonjić ◽  
E. Muñoz ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Perturbation Theory ◽  
First Principles ◽  
Density Functional ◽  
Kondo Effect ◽  
Strongly Correlated ◽  
Functional Theory ◽  
Molecular Conductance ◽  
Non Equilibrium

We predict the non-equilibrium molecular conductance in the Kondo regime from first principles by combining density functional theory with the renormalized super-perturbation theory.

scholarly journals Dzyaloshinskii–Moriya Coupling in 3d Insulators

2019 ◽  
Vol 4 (4) ◽  
pp. 84 ◽  
Author(s):  
Alexander Moskvin
Keyword(s):  
Density Functional ◽  
Microscopic Theory ◽  
Strongly Correlated ◽  
Spin Orbital ◽  
Functional Theory ◽  
Different Types ◽  
Theoretical Results ◽  
Spin Orbital Coupling ◽  
Density Transfer ◽  
Super Exchange Interaction

We present an overview of the microscopic theory of the Dzyaloshinskii–Moriya (DM) coupling in strongly correlated 3d compounds. Most attention in the paper centers around the derivation of the Dzyaloshinskii vector, its value, orientation, and sense (sign) under different types of the (super)exchange interaction and crystal field. We consider both the Moriya mechanism of the antisymmetric interaction and novel contributions, in particular, that of spin–orbital coupling on the intermediate ligand ions. We have predicted a novel magnetic phenomenon, weak ferrimagnetism in mixed weak ferromagnets with competing signs of Dzyaloshinskii vectors. We revisit a problem of the DM coupling for a single bond in cuprates specifying the local spin–orbital contributions to the Dzyaloshinskii vector focusing on the oxygen term. We predict a novel puzzling effect of the on-site staggered spin polarization to be a result of the on-site spin–orbital coupling and the cation-ligand spin density transfer. The intermediate ligand nuclear magnetic resonance (NMR) measurements are shown to be an effective tool to inspect the effects of the DM coupling in an external magnetic field. We predict the effect of a strong oxygen-weak antiferromagnetism in edge-shared CuO 2 chains due to uncompensated oxygen Dzyaloshinskii vectors. We revisit the effects of symmetric spin anisotropy directly induced by the DM coupling. A critical analysis will be given of different approaches to exchange-relativistic coupling based on the cluster and the DFT (density functional theory) based calculations. Theoretical results are applied to different classes of 3d compounds from conventional weak ferromagnets ( α -Fe 2 O 3 , FeBO 3 , FeF 3 , RFeO 3 , RCrO 3 , ...) to unconventional systems such as weak ferrimagnets (e.g., RFe 1 - x Cr x O 3 ), helimagnets (e.g., CsCuCl 3 ), and parent cuprates (La 2 CuO 4 , ...).

Density Functional Theory Modeling of Low-Loss Electron Energy-Loss Spectroscopy in Wurtzite III-Nitride Ternary Alloys

2016 ◽  
Vol 22 (3) ◽  
pp. 706-716 ◽  
Author(s):  
Alberto Eljarrat ◽  
Xavier Sastre ◽  
Francesca Peiró ◽  
Sónia Estradé
Keyword(s):  
Density Functional Theory ◽  
Band Structure ◽  
Energy Loss ◽  
Dielectric Response ◽  
Density Functional ◽  
Ternary Alloys ◽  
Low Loss ◽  
Plasmon Energy ◽  
Functional Theory ◽  
Electron Energy Loss

AbstractIn the present work, the dielectric response of III-nitride semiconductors is studied using density functional theory (DFT) band structure calculations. The aim of this study is to improve our understanding of the features in the low-loss electron energy-loss spectra of ternary alloys, but the results are also relevant to optical and UV spectroscopy results. In addition, the dependence of the most remarkable features with composition is tested, i.e. applying Vegard’s law to band gap and plasmon energy. For this purpose, three wurtzite ternary alloys, from the combination of binaries AlN, GaN, and InN, were simulated through a wide compositional range (i.e., AlxGa1−xN, InxAl1−xN, and InxGa1−xN, with x=[0,1]). For this DFT calculations, the standard tools found in Wien2k software were used. In order to improve the band structure description of these semiconductor compounds, the modified Becke–Johnson exchange–correlation potential was also used. Results from these calculations are presented, including band structure, density of states, and complex dielectric function for the whole compositional range. Larger, closer to experimental values, band gap energies are predicted using the novel potential, when compared with standard generalized gradient approximation. Moreover, a detailed analysis of the collective excitation features in the dielectric response reveals their compositional dependence, which sometimes departs from a linear behavior (bowing). Finally, an advantageous method for measuring the plasmon energy dependence from these calculations is explained.

FIRST-PRINCIPLES STUDY OF THE ELECTRONIC, LINEAR, AND NONLINEAR OPTICAL PROPERTIES OF Li(Nb, Ta)O3

2010 ◽  
Vol 24 (32) ◽  
pp. 6277-6290 ◽  
Author(s):  
SULEYMAN CABUK
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Nonlinear Optical ◽  
Energy Gap ◽  
Local Density ◽  
Theoretical Calculations ◽  
Total Density ◽  
Functional Theory ◽  
Experimental Values ◽  
Electron Energy Loss

We investigate the energy band structure, total density of states, the linear, nonlinear optical (NLO) response, and the electron energy-loss spectrum for Li(Nb, Ta)O 3 using first principles calculations based on density functional theory in its local density approximation. Our calculation shows that these compounds have similar structures. The indirect band gaps of 3.39 eV (LiNbO3) and 3.84 eV (LiTaO3) at the Γ–Z direction in the Brillouin zone are found. A simple scissor approximation is applied to adjust the band energy gap from the calculations to match the experimental values. The optical spectra are analyzed and the origins of some of the peaks in the spectra are discussed in terms of calculated electronic structure. Calculations are reported for the frequency-dependent complex second-order NLO susceptibilities [Formula: see text] up to 10 eV and for zero-frequency limit [Formula: see text]. The results are compared with the theoretical calculations and the available experimental data.

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