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Typical higher-order topological systems require the fine-tuning of hopping textures and external fields, which considerably hinders their practical realization. Based on a simple picture that corners are “edges” of edges, we determine that in the already-thoroughly-studied monolayer graphene, higher-order topological corner states appear without introducing any additional effects. Unlike quadrupole insulators, owing to degenerate Dirac points in graphene, the emergence of topological corner states depends on the corner angle and edge geometries. We provide a useful expression for the indication of corner states in graphene by the product of Zak phases. We also discuss the methods for experimental detection of the nontrivial higher-order topology in graphene such as the fractional corner anomaly and the disparity of local density of states between trivial and nontrivial corners.
Feng Liu; Katsunori Wakabayashi. Higher-order topology and fractional charge in monolayer graphene. Physical Review Research 2021, 3, 023121 .
AMA StyleFeng Liu, Katsunori Wakabayashi. Higher-order topology and fractional charge in monolayer graphene. Physical Review Research. 2021; 3 (2):023121.
Chicago/Turabian StyleFeng Liu; Katsunori Wakabayashi. 2021. "Higher-order topology and fractional charge in monolayer graphene." Physical Review Research 3, no. 2: 023121.
The graphene edge state is essential for graphene electronics and fundamental in graphene theory, however it is not observed in deposited graphene. Here we report the discovery of the epigraphene edge state (EGES) in conventionally patterned epigraphene using plasma-based lithography that stabilizes and passivates the edges probably by fusing the graphene edges to the non-polar silicon carbide substrate, as expected. Transport involves a single, essentially dissipationless conductance channel at zero energy up to room temperature. The Fermi level is pinned at zero energy. The EGES does not generate a Hall voltage and the usual quantum Hall effect is observed only after subtraction of the EGES current. EGES transport is highly protected and apparently mediated by an unconventional zero-energy fermion that is half electron and half hole. Interconnected networks involving only the EGES can be patterned, opening the door to a new graphene nanoelectronics paradigm that is relevant for quantum computing.
Vladimir Prudkovskiy; Yiran Hu; Kaimin Zhang; Yue Hu; Peixuan Ji; Grant Nunn; Jian Zhao; Chengqian Shi; Antonio Tejeda; David Wander; Alessandro de Cecco; Clemens Winkelmann; Yuxuan Jiang; Tianhao Zhao; Katsunori Wakabayashi; Zhigang Jiang; Lei Ma; Claire Berger; Walt de Heer. Dissipationless zero energy epigraphene edge state for nanoelectronics. 2021, 1 .
AMA StyleVladimir Prudkovskiy, Yiran Hu, Kaimin Zhang, Yue Hu, Peixuan Ji, Grant Nunn, Jian Zhao, Chengqian Shi, Antonio Tejeda, David Wander, Alessandro de Cecco, Clemens Winkelmann, Yuxuan Jiang, Tianhao Zhao, Katsunori Wakabayashi, Zhigang Jiang, Lei Ma, Claire Berger, Walt de Heer. Dissipationless zero energy epigraphene edge state for nanoelectronics. . 2021; ():1.
Chicago/Turabian StyleVladimir Prudkovskiy; Yiran Hu; Kaimin Zhang; Yue Hu; Peixuan Ji; Grant Nunn; Jian Zhao; Chengqian Shi; Antonio Tejeda; David Wander; Alessandro de Cecco; Clemens Winkelmann; Yuxuan Jiang; Tianhao Zhao; Katsunori Wakabayashi; Zhigang Jiang; Lei Ma; Claire Berger; Walt de Heer. 2021. "Dissipationless zero energy epigraphene edge state for nanoelectronics." , no. : 1.
Monolayer NbSe2 is a metallic two-dimensional (2D) transition-metal dichalcogenide material. Owing to the lattice structure and the strong atomic spin-orbit coupling (SOC) field, monolayer NbSe2 possesses Ising-type SOC which acts as an effective Zeeman field, leading to the unconventional topological spin properties. In this paper, we numerically calculate spin-dependent optical conductivity of monolayer NbSe2 using Kubo formula based on an effective tight-binding model which includes dz2, dx2−y2, and dxy orbitals of Nb atoms. Numerical calculation indicates that the up- and down-spin have opposite sign of Hall current, so the pure spin Hall current can be generated in monolayer NbSe2 under light irradiation, owing to the topological nature of monolayer NbSe2, i.e., finite spin Berry curvature. The spin Hall angle is also evaluated. The optically induced spin Hall current can be enhanced by the electron doping and persists even at room temperature. Our results will serve to design opt-spintronics devices such as spin current harvesting by light irradiation on the basis of 2D materials.
Ren Habara; Katsunori Wakabayashi. Optically induced spin current in monolayer NbSe2. Physical Review B 2021, 103, L161410 .
AMA StyleRen Habara, Katsunori Wakabayashi. Optically induced spin current in monolayer NbSe2. Physical Review B. 2021; 103 (16):L161410.
Chicago/Turabian StyleRen Habara; Katsunori Wakabayashi. 2021. "Optically induced spin current in monolayer NbSe2." Physical Review B 103, no. 16: L161410.
We theoretically investigate high-pressure effects on the atomic dynamics of metallic glasses. The theory predicts compression-induced rejuvenation and the resulting strain hardening that have been recently observed in metallic glasses. Structural relaxation under pressure is mainly governed by local cage dynamics. The external pressure restricts the dynamical constraints and slows down the atomic mobility. In addition, the compression induces a rejuvenated metastable state (local minimum) at a higher energy in the free-energy landscape. Thus, compressed metallic glasses can rejuvenate and the corresponding relaxation is reversible. This behavior leads to strain hardening in mechanical deformation experiments. Theoretical predictions agree well with experiments.
Anh D. Phan; Alessio Zaccone; Vu D. Lam; Katsunori Wakabayashi. Theory of Pressure-Induced Rejuvenation and Strain Hardening in Metallic Glasses. Physical Review Letters 2021, 126, 025502 .
AMA StyleAnh D. Phan, Alessio Zaccone, Vu D. Lam, Katsunori Wakabayashi. Theory of Pressure-Induced Rejuvenation and Strain Hardening in Metallic Glasses. Physical Review Letters. 2021; 126 (2):025502.
Chicago/Turabian StyleAnh D. Phan; Alessio Zaccone; Vu D. Lam; Katsunori Wakabayashi. 2021. "Theory of Pressure-Induced Rejuvenation and Strain Hardening in Metallic Glasses." Physical Review Letters 126, no. 2: 025502.
We theoretically investigate equilibrium behaviors and photothermal effects of a flexible plasmonic metamaterial composed of aramid nanofibers and gold nanoparticles.
Anh D. Phan; Vu D. Lam; Katsunori Wakabayashi. Cooperative nanoparticle self-assembly and photothermal heating in a flexible plasmonic metamaterial. RSC Advances 2020, 10, 41830 -41836.
AMA StyleAnh D. Phan, Vu D. Lam, Katsunori Wakabayashi. Cooperative nanoparticle self-assembly and photothermal heating in a flexible plasmonic metamaterial. RSC Advances. 2020; 10 (68):41830-41836.
Chicago/Turabian StyleAnh D. Phan; Vu D. Lam; Katsunori Wakabayashi. 2020. "Cooperative nanoparticle self-assembly and photothermal heating in a flexible plasmonic metamaterial." RSC Advances 10, no. 68: 41830-41836.
We theoretically investigate structural relaxation and activated diffusion of glass-forming liquids at different pressures using both Elastically Collective Nonlinear Langevin Equation (ECNLE) theory and molecular dynamics (MD) simulations.
Anh D. Phan; Kajetan Koperwas; Marian Paluch; Katsunori Wakabayashi. Coupling between structural relaxation and diffusion in glass-forming liquids under pressure variation. Physical Chemistry Chemical Physics 2020, 22, 24365 -24371.
AMA StyleAnh D. Phan, Kajetan Koperwas, Marian Paluch, Katsunori Wakabayashi. Coupling between structural relaxation and diffusion in glass-forming liquids under pressure variation. Physical Chemistry Chemical Physics. 2020; 22 (42):24365-24371.
Chicago/Turabian StyleAnh D. Phan; Kajetan Koperwas; Marian Paluch; Katsunori Wakabayashi. 2020. "Coupling between structural relaxation and diffusion in glass-forming liquids under pressure variation." Physical Chemistry Chemical Physics 22, no. 42: 24365-24371.
The photothermal energy conversion in hanging and floating polyaniline (PANi)-cotton fabrics is investigated using a model based on the heat diffusion equation.
Do T. Nga; Anh D. Phan; Vu D. Lam; Lilia M. Woods; Katsunori Wakabayashi. Enhanced solar photothermal effect of PANi fabrics with plasmonic nanostructures. RSC Advances 2020, 10, 28447 -28453.
AMA StyleDo T. Nga, Anh D. Phan, Vu D. Lam, Lilia M. Woods, Katsunori Wakabayashi. Enhanced solar photothermal effect of PANi fabrics with plasmonic nanostructures. RSC Advances. 2020; 10 (47):28447-28453.
Chicago/Turabian StyleDo T. Nga; Anh D. Phan; Vu D. Lam; Lilia M. Woods; Katsunori Wakabayashi. 2020. "Enhanced solar photothermal effect of PANi fabrics with plasmonic nanostructures." RSC Advances 10, no. 47: 28447-28453.
2D van der Waals ferroelectrics have emerged as an attractive building block with immense potential to provide multifunctionality in nanoelectronics. Although several accomplishments have been reported in ferroelectric switching for out-of-plane ferroelectrics down to the monolayer, a purely in-plane ferroelectric has not been experimentally validated at the monolayer thickness. Herein, an in-plane ferroelectricity is demonstrated for micrometer-size monolayer SnS at room temperature. SnS has been commonly regarded to exhibit the odd–even effect, where the centrosymmetry breaks only in the odd-number layers to exhibit ferroelectricity. Remarkably, however, a robust room temperature ferroelectricity exists in SnS below a critical thickness of 15 layers with both an odd and even number of layers, suggesting the possibility of controlling the stacking sequence of multilayer SnS beyond the limit of ferroelectricity in the monolayer. This work will pave the way for nanoscale ferroelectric applications based on SnS as a platform for in-plane ferroelectrics.
Naoki Higashitarumizu; Hayami Kawamoto; Chien-Ju Lee; Bo-Han Lin; Fu-Hsien Chu; Itsuki Yonemori; Tomonori Nishimura; Katsunori Wakabayashi; Wen-Hao Chang; Kosuke Nagashio. Purely in-plane ferroelectricity in monolayer SnS at room temperature. Nature Communications 2020, 11, 1 -9.
AMA StyleNaoki Higashitarumizu, Hayami Kawamoto, Chien-Ju Lee, Bo-Han Lin, Fu-Hsien Chu, Itsuki Yonemori, Tomonori Nishimura, Katsunori Wakabayashi, Wen-Hao Chang, Kosuke Nagashio. Purely in-plane ferroelectricity in monolayer SnS at room temperature. Nature Communications. 2020; 11 (1):1-9.
Chicago/Turabian StyleNaoki Higashitarumizu; Hayami Kawamoto; Chien-Ju Lee; Bo-Han Lin; Fu-Hsien Chu; Itsuki Yonemori; Tomonori Nishimura; Katsunori Wakabayashi; Wen-Hao Chang; Kosuke Nagashio. 2020. "Purely in-plane ferroelectricity in monolayer SnS at room temperature." Nature Communications 11, no. 1: 1-9.
We theoretically investigate glass transition behaviors of the glassy graphene in a wide range of temperature, where this amorphous graphene is described as a hard-sphere fluid. The dynamic arrest of a particle is assumingly caused by interactions with its nearest neighbors and surrounding fluid particles. The assumption allows us to analyze roles of local and collective particle mobility. We calculate the temperature dependence of structural relaxation time and dynamic shear modulus, the dynamic fragility, and the glass transition temperature. In addition, correlations between these physical quantities are comprehensively discussed. Our theoretical calculations agree quantitatively well with recent simulations and Dyre’s shoving model.
Tran Dinh Cuong; Anh D. Phan; Katsunori Wakabayashi; Pham Thanh Huy. Structural relaxation time and dynamic shear modulus of glassy graphene. Journal of Non-Crystalline Solids 2020, 538, 120024 .
AMA StyleTran Dinh Cuong, Anh D. Phan, Katsunori Wakabayashi, Pham Thanh Huy. Structural relaxation time and dynamic shear modulus of glassy graphene. Journal of Non-Crystalline Solids. 2020; 538 ():120024.
Chicago/Turabian StyleTran Dinh Cuong; Anh D. Phan; Katsunori Wakabayashi; Pham Thanh Huy. 2020. "Structural relaxation time and dynamic shear modulus of glassy graphene." Journal of Non-Crystalline Solids 538, no. : 120024.
The optical properties of triptycene molecular membranes (TMMs) under the linearly and circularly polarized light irradiation have been theoretically studied. Since TMMs have the double-layered kagome lattice structures for their π electrons, i.e., tiling of trigonal- and hexagonal-symmetric rings, the electronic band structures of TMMs have nonequivalent Dirac cones and perfect flat bands. By constructing the tight-binding model to describe the π-electronic states of TMMs, we have evaluated the optical absorption intensities and valley selective excitation of TMMs based on the Kubo formula. It is found that absorption intensities crucially depend on both the light polarization angle and the excitation position in momentum space, i.e., the momentum and valley selective optical excitation. The polarization dependence and optical selection rules are also clarified by using group theoretical analyses.
Masashi Akita; Yasumaru Fujii; Mina Maruyama; Susumu Okada; Katsunori Wakabayashi. Momentum-selective optical absorption in triptycene molecular membrane. Physical Review B 2020, 101, 085418 .
AMA StyleMasashi Akita, Yasumaru Fujii, Mina Maruyama, Susumu Okada, Katsunori Wakabayashi. Momentum-selective optical absorption in triptycene molecular membrane. Physical Review B. 2020; 101 (8):085418.
Chicago/Turabian StyleMasashi Akita; Yasumaru Fujii; Mina Maruyama; Susumu Okada; Katsunori Wakabayashi. 2020. "Momentum-selective optical absorption in triptycene molecular membrane." Physical Review B 101, no. 8: 085418.
We theoretically investigate the plasmonic properties of mid-infrared graphene-based metamaterials and apply deep learning of a neural network for the inverse design. These artificial structures have square periodic arrays of graphene plasmonic resonators deposited on dielectric thin films. Optical spectra vary significantly with changes in structural parameters. To validate our theoretical approach, we carry out finite difference time domain simulations and compare computational results with theoretical calculations. Quantitatively good agreements among theoretical predictions, simulations, and previous experiments allow us to employ this proposed theoretical model to generate reliable data for training and testing deep neural networks. By merging the pre-trained neural network with the inverse network, we implement calculations for inverse design of the graphene-based metameterials. We also discuss the limitation of the data-driven approach.
Anh D. Phan; Cuong V. Nguyen; Pham T. Linh; Tran V. Huynh; Vu Dinh Lam; Anh-Tuan Le; Katsunori Wakabayashi; The Linh Pham. Deep Learning for the Inverse Design of Mid-Infrared Graphene Plasmons. Crystals 2020, 10, 125 .
AMA StyleAnh D. Phan, Cuong V. Nguyen, Pham T. Linh, Tran V. Huynh, Vu Dinh Lam, Anh-Tuan Le, Katsunori Wakabayashi, The Linh Pham. Deep Learning for the Inverse Design of Mid-Infrared Graphene Plasmons. Crystals. 2020; 10 (2):125.
Chicago/Turabian StyleAnh D. Phan; Cuong V. Nguyen; Pham T. Linh; Tran V. Huynh; Vu Dinh Lam; Anh-Tuan Le; Katsunori Wakabayashi; The Linh Pham. 2020. "Deep Learning for the Inverse Design of Mid-Infrared Graphene Plasmons." Crystals 10, no. 2: 125.
Compression effects on alpha and beta relaxation process of amorphous drugs are theoretically investigated by developing the elastically collective nonlinear Langevin equation theory. We describe the structural relaxation as a coupling between local and nonlocal activated process. Meanwhile, the secondary beta process is mainly governed by the nearest-neighbor interactions of a molecule. This assumption implies the beta relaxation acts as a precursor of the alpha relaxation. When external pressure is applied, a small displacement of a molecule is additionally exerted by a pressure-induced mechanical work in the dynamic free energy, which quantifies interactions between a molecule with its nearest neighbors. The local dynamics has more restriction and it induces stronger effects of collective motions on single-molecule dynamics. Thus, the alpha and beta relaxation times are significantly slowed down with increasing compression. We apply this approach to determine the temperature and pressure dependence of the alpha and beta relaxation time for curcumin, glibenclamide, and indomethacin, and compare numerical results with prior experimental studies. Both qualitative and quantitative agreement between theoretical calculations and experiments validate our assumptions and reveal their limitations. Our approach would pave the way for the development of the drug formulation process.
Anh D. Phan; Katsunori Wakabayashi. Theory of Structural and Secondary Relaxation in Amorphous Drugs under Compression. Pharmaceutics 2020, 12, 177 .
AMA StyleAnh D. Phan, Katsunori Wakabayashi. Theory of Structural and Secondary Relaxation in Amorphous Drugs under Compression. Pharmaceutics. 2020; 12 (2):177.
Chicago/Turabian StyleAnh D. Phan; Katsunori Wakabayashi. 2020. "Theory of Structural and Secondary Relaxation in Amorphous Drugs under Compression." Pharmaceutics 12, no. 2: 177.
The relaxation dynamics and thermodynamic properties of supercooled and glassy gambogic acid are investigated using both theory and experiment. We measure the temperature dependence of the relaxation times in three polymorphs (α-, β-, and γ-form). To gain insight into the relaxation processes, we propose a theoretical approach to quantitatively understand the nature of these three relaxations. The α-relaxation captures cooperative motions of molecules, while the β-process is mainly governed by the local dynamics of a single molecule within the cage formed by its nearest neighbors. Based on quantitative agreement between theory and experimental data, our calculations clearly indicate that the β-process is a precursor of the structural relaxation and intramolecular motions are responsible for the γ-relaxation. Moreover, the approach is exploited to study the effects of the heating process on alpha relaxation. We find that the heating rate varies logarithmically with Tg and 1000/Tg. These variations are qualitatively consistent with many prior studies.
Anh D. Phan; Tran Thi Thu Thuy; Nguyen Thi Kim An; Justyna Knapik-Kowalczuk; Marian Paluch; Katsunori Wakabayashi. Molecular relaxations in supercooled liquid and glassy states of amorphous gambogic acid: Dielectric spectroscopy, calorimetry, and theoretical approach. AIP Advances 2020, 10, 025128 .
AMA StyleAnh D. Phan, Tran Thi Thu Thuy, Nguyen Thi Kim An, Justyna Knapik-Kowalczuk, Marian Paluch, Katsunori Wakabayashi. Molecular relaxations in supercooled liquid and glassy states of amorphous gambogic acid: Dielectric spectroscopy, calorimetry, and theoretical approach. AIP Advances. 2020; 10 (2):025128.
Chicago/Turabian StyleAnh D. Phan; Tran Thi Thu Thuy; Nguyen Thi Kim An; Justyna Knapik-Kowalczuk; Marian Paluch; Katsunori Wakabayashi. 2020. "Molecular relaxations in supercooled liquid and glassy states of amorphous gambogic acid: Dielectric spectroscopy, calorimetry, and theoretical approach." AIP Advances 10, no. 2: 025128.
Theoretical approaches are formulated to investigate the molecular mobility under various cooling rates of amorphous drugs.
Anh D. Phan; Katsunori Wakabayashi; Marian Paluch; Vu D. Lam. Effects of cooling rate on structural relaxation in amorphous drugs: elastically collective nonlinear langevin equation theory and machine learning study. RSC Advances 2019, 9, 40214 -40221.
AMA StyleAnh D. Phan, Katsunori Wakabayashi, Marian Paluch, Vu D. Lam. Effects of cooling rate on structural relaxation in amorphous drugs: elastically collective nonlinear langevin equation theory and machine learning study. RSC Advances. 2019; 9 (69):40214-40221.
Chicago/Turabian StyleAnh D. Phan; Katsunori Wakabayashi; Marian Paluch; Vu D. Lam. 2019. "Effects of cooling rate on structural relaxation in amorphous drugs: elastically collective nonlinear langevin equation theory and machine learning study." RSC Advances 9, no. 69: 40214-40221.
The Su-Schrieffer-Heeger (SSH) model on a two-dimensional square lattice exhibits a topological phase transition which is related to the Zak phase determined by bulk band topology. The strong modulation of electron hopping causes nontrivial charge polarization even in the presence of inversion symmetry. The energy band structures and topological edge states have been calculated numerically in previous studies. Here, however, the full energy spectrum and explicit form of wave functions for two-dimensional bulk and one-dimensional ribbon geometries of the SSH model are analytically derived using the wave mechanics approach. Explicit analytic representations of wave functions provide the information of parity for each subband, localization length, and critical point of the topological phase transition in the SSH ribbon. IThe dimensional crossover of the topological transition point for the SSH model from one to two dimensions is also shown.
Daichi Obana; Feng Liu; Katsunori Wakabayashi. Topological edge states in the Su-Schrieffer-Heeger model. Physical Review B 2019, 100, 075437 .
AMA StyleDaichi Obana, Feng Liu, Katsunori Wakabayashi. Topological edge states in the Su-Schrieffer-Heeger model. Physical Review B. 2019; 100 (7):075437.
Chicago/Turabian StyleDaichi Obana; Feng Liu; Katsunori Wakabayashi. 2019. "Topological edge states in the Su-Schrieffer-Heeger model." Physical Review B 100, no. 7: 075437.
We propose a theoretical approach to describe quantitatively the heating process in aqueous solutions of dispersed TiN nanoparticles under solar illumination.
Anh D. Phan; Nam B. Le; T. H. Lien Nghiem; Lilia M. Woods; Satoshi Ishii; Katsunori Wakabayashi. Confinement effects on the solar thermal heating process of TiN nanoparticle solutions. Physical Chemistry Chemical Physics 2019, 21, 19915 -19920.
AMA StyleAnh D. Phan, Nam B. Le, T. H. Lien Nghiem, Lilia M. Woods, Satoshi Ishii, Katsunori Wakabayashi. Confinement effects on the solar thermal heating process of TiN nanoparticle solutions. Physical Chemistry Chemical Physics. 2019; 21 (36):19915-19920.
Chicago/Turabian StyleAnh D. Phan; Nam B. Le; T. H. Lien Nghiem; Lilia M. Woods; Satoshi Ishii; Katsunori Wakabayashi. 2019. "Confinement effects on the solar thermal heating process of TiN nanoparticle solutions." Physical Chemistry Chemical Physics 21, no. 36: 19915-19920.
Topological phonics has emerged as a novel approach to engineer the flow of light and provides unprecedented means for developing diverse photonic elements, including robust optical waveguides immune to structural imperfections. However, the development of nanoscale standing-wave cavities in topological photonics is rather slow, despite its importance when building densely-integrated photonic integrated circuits. In this Letter, we report a photonic crystal nanocavity based on a topological corner state, supported at a 90-degrees-angled rim of a two dimensional photonic crystal. A combination of the bulk-edge and edge-corner correspondences guarantees the presence of the higher-order topological state in a hierarchical manner. We experimentally observed a corner mode that is tightly localized in space while supporting a high Q factor over 2,000, verifying its promise as a nanocavity. These results cast new light on the way to introduce nanocavities in topological photonics platforms.
Yasutomo Ota; Feng Liu; Ryota Katsumi; Katsuyuki Watanabe; Katsunori Wakabayashi; Yasuhiko Arakawa; Satoshi Iwamoto. Photonic crystal nanocavity based on a topological corner state. 2018, 1 .
AMA StyleYasutomo Ota, Feng Liu, Ryota Katsumi, Katsuyuki Watanabe, Katsunori Wakabayashi, Yasuhiko Arakawa, Satoshi Iwamoto. Photonic crystal nanocavity based on a topological corner state. . 2018; ():1.
Chicago/Turabian StyleYasutomo Ota; Feng Liu; Ryota Katsumi; Katsuyuki Watanabe; Katsunori Wakabayashi; Yasuhiko Arakawa; Satoshi Iwamoto. 2018. "Photonic crystal nanocavity based on a topological corner state." , no. : 1.
Recent progress in transition-metal dichalcogenides has opened up new possibilities of atomically thin nanomaterial based electronic device applications. Here we investigate atomic-scale self-assembled heterojunction modulated by layer-by-layer controlled oxidation in mono and few layer dichalcogenide systems and their electronic properties within first-principles framework. Pristine dichalcogenide systems exhibit semiconducting behavior. We observe reduction of the band gap for partial oxidation of the top layer. However, complete oxidation of the top layer makes the system metallic, owing to the charge transfer from pristine to oxidized layer, as observed in recent experiments. When the bottom layer gets partially oxidized with fully oxidized top layers, the system shows unprecedented semimetallic behavior. The appearance of valence band maximum and conduction band minimum at different k-points can introduce valley polarization. Therefore, our study shows controlled oxidation induced varying electronic properties in dichalcogenide based heterojunctions that can be exploited for advanced electronic, opto-electronic and valleytronic device applications.
Soumya Ranjan Das; Katsunori Wakabayashi; Mahito Yamamoto; Kazuhito Tsukagoshi; Sudipta Dutta. Layer-by-Layer Oxidation Induced Electronic Properties in Transition-Metal Dichalcogenides. The Journal of Physical Chemistry C 2018, 122, 17001 -17007.
AMA StyleSoumya Ranjan Das, Katsunori Wakabayashi, Mahito Yamamoto, Kazuhito Tsukagoshi, Sudipta Dutta. Layer-by-Layer Oxidation Induced Electronic Properties in Transition-Metal Dichalcogenides. The Journal of Physical Chemistry C. 2018; 122 (29):17001-17007.
Chicago/Turabian StyleSoumya Ranjan Das; Katsunori Wakabayashi; Mahito Yamamoto; Kazuhito Tsukagoshi; Sudipta Dutta. 2018. "Layer-by-Layer Oxidation Induced Electronic Properties in Transition-Metal Dichalcogenides." The Journal of Physical Chemistry C 122, no. 29: 17001-17007.
Based on density functional theory with the generalized gradient approximation, we have investigated the geometric and electronic structures of two-dimensional hexagonal covalent networks consisting of oligoacenes and fourfold coordinated hydrocarbon atoms, which are alternately arranged in a hexagonal manner. All networks were semiconductors with a finite energy gap at the Γ point, which monotonically decreased with the increase of the oligoacene length. As a result of a Kagome network of oligoacene connected through sp3 C atoms, the networks possess peculiar electron states in their valence and conduction bands, which consist of a flat dispersion band and a Dirac cone. The total energy of the networks depends on the oligoacene length and has a minimum for the network comprising naphthalene.
Yasumaru Fujii; Mina Maruyama; Katsunori Wakabayashi; Kyoko Nakada; Susumu Okada. Electronic Structure of Two-Dimensional Hydrocarbon Networks of sp2 and sp3 C Atoms. Journal of the Physical Society of Japan 2018, 87, 034704 .
AMA StyleYasumaru Fujii, Mina Maruyama, Katsunori Wakabayashi, Kyoko Nakada, Susumu Okada. Electronic Structure of Two-Dimensional Hydrocarbon Networks of sp2 and sp3 C Atoms. Journal of the Physical Society of Japan. 2018; 87 (3):034704.
Chicago/Turabian StyleYasumaru Fujii; Mina Maruyama; Katsunori Wakabayashi; Kyoko Nakada; Susumu Okada. 2018. "Electronic Structure of Two-Dimensional Hydrocarbon Networks of sp2 and sp3 C Atoms." Journal of the Physical Society of Japan 87, no. 3: 034704.
Topological photonic crystals are designed based on the concept of Zak's phase rather than the topological invariants such as the Chern number and spin Chern number, which rely on the existence of a nonvanishing Berry curvature. Our photonic crystals (PCs) are made of pure dielectrics and sit on a square lattice obeying the C4v point-group symmetry. Two varieties of PCs are considered: one closely resembles the electronic two-dimensional Su-Schrieffer-Heeger model, and the other continues as an extension of this analogy. In both cases, the topological transitions are induced by adjusting the lattice constants. Topological edge modes (TEMs) are shown to exist within the nontrivial photonic band gaps on the termination of those PCs. The high efficiency of these TEMs transferring electromagnetic energy against several types of disorders has been demonstrated using the finite-element method.
Feng Liu; Hai-Yao Deng; Katsunori Wakabayashi. Topological photonic crystals with zero Berry curvature. Physical Review B 2018, 97, 035442 .
AMA StyleFeng Liu, Hai-Yao Deng, Katsunori Wakabayashi. Topological photonic crystals with zero Berry curvature. Physical Review B. 2018; 97 (3):035442.
Chicago/Turabian StyleFeng Liu; Hai-Yao Deng; Katsunori Wakabayashi. 2018. "Topological photonic crystals with zero Berry curvature." Physical Review B 97, no. 3: 035442.