The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Nobuo Ueno - One of the best experts on this subject based on the ideXlab platform.
-
accessing the conduction Band Dispersion in ch3nh3pbi3 single crystals
Journal of Physical Chemistry Letters, 2021Co-Authors: Jin-peng Yang, Nobuo Ueno, Hiroyuki Yoshida, Haruki Sato, Hibiki Orio, Xianjie Liu, Mats Fahlman, Takashi Yamada, Satoshi KeraAbstract:The conduction Band Dispersion in methylammonium lead iodide (CH3NH3PbI3) was studied by both angle-resolved two-photon photoelectron spectroscopy (AR-2PPE) with low photon intensity (∼0.0125 nJ/pulse) and angle-resolved low-energy inverse photoelectron spectroscopy (AR-LEIPS). Clear energy Dispersion of the conduction Band along the Γ-M direction was first observed by these independent methods under different temperatures, and the Dispersion was found to be consistent with Band calculation under the cubic phase. The effective mass of the electrons at the Γ point was estimated to be (0.20 ± 0.05)m0 at the temperature of 90 K. The observed conduction Band energy was different between the AR-LEIPS and AR-2PPE, which was ascribed to the electronic-correlation-dependent difference of initial and final states probing processes. The present results also indicate that the surface structure in CH3NH3PbI3 provides the cubic-dominated electronic property even at lower temperatures.
-
Accessing the conduction Band Dispersion in CH3NH3PbI3 single crystals.
arXiv: Materials Science, 2020Co-Authors: Jin-peng Yang, Nobuo Ueno, Hiroyuki Yoshida, Haruki Sato, Hibiki Orio, Xianjie Liu, Mats Fahlman, Takashi Yamada, Satoshi KeraAbstract:The conduction Band structure in methylammonium lead iodide (CH3NH3PbI3) was studied both by angle-resolved two-photon photoemission spectroscopy (AR-2PPE) with low-photon intensity and angle-resolved low-energy inverse photoelectron spectroscopy (AR-LEIPS). Clear energy Dispersion of the conduction Band along the {\Gamma}M direction was observed by these independent methods under different temperatures, and the Dispersion was found to be consistent with Band calculations under the cubic phase. The effective mass of the electrons at the {\Gamma} point was estimated to be (0.20+-0.05)m0 at 90 K. The observed energy position was largely different between the AR-LEIPS and AR-2PPE, demonstrating the electron correlation effects on the Band structures. The present results also indicate that the surface structure in CH3NH3PbI3 provides the cubic-dominated electronic property even at lower temperatures.
-
intermolecular Band Dispersion in a self assembled phthalocyanine derivative film the case of tetrakis thiadiazole porhyrazine
Physical Review B, 2010Co-Authors: Yusuke Tanaka, Kouji Takahashi, Takuya Kuzumaki, Yuta Yamamoto, Kunihiro Hotta, Ayumi Harasawa, Yasuhito Miyoshi, Hirofumi Yoshikawa, Yukio Ouchi, Nobuo UenoAbstract:The electronic Band structure of a tetrakis(thiadiazole)porhyrazine $({\text{H}}_{2}\text{TTDPz})$ thin film prepared on ${\text{SiO}}_{2}$, which is a system close to a real device one, was studied by photoelectron spectroscopy (PES). Although the film was grown on a bumpy surface, clear electronic Band Dispersion was observed along the surface-normal direction. The Bandwidth of the highest occupied molecular orbital (HOMO) Band was approximately 180 meV. By analyzing the PES result using the tight-binding method, the transfer integral for the $\ensuremath{\pi}\text{\ensuremath{-}}\ensuremath{\pi}$ interaction, the effective mass of the HOMO hole, and the hole mobility were estimated to be approximately $45\ifmmode\pm\else\textpm\fi{}10\text{ }\text{meV}$, $1/{m}_{h}^{\ensuremath{\ast}}=(0.14\ifmmode\pm\else\textpm\fi{}0.03)/{m}_{0}$, and ${\ensuremath{\mu}}_{h}=8.2\ifmmode\pm\else\textpm\fi{}1.8\text{ }{\text{cm}}^{2}/\text{V}\text{ }\text{s}$, respectively, at 100 K.
-
highest occupied molecular orbital Band Dispersion of rubrene single crystals as observed by angle resolved ultraviolet photoelectron spectroscopy
Physical Review Letters, 2010Co-Authors: Shin Ichi Machida, Nobuo Ueno, Steffen Duhm, Qian Xin, Satoshi Kera, Yasuo Nakayama, Akihiro Funakoshi, Naoki Ogawa, Hisao IshiiAbstract:The electronic structure of rubrene single crystals was studied by angle-resolved ultraviolet photoelectron spectroscopy. A clear energy Dispersion of the highest occupied molecular orbital-derived Band was observed, and the Dispersion width was found to be 0.4 eV along the well-stacked direction. The effective mass of the holes was estimated to be $0.65(\ifmmode\pm\else\textpm\fi{}0.1){m}_{0}$. The present results suggest that the carrier conduction mechanism in rubrene single crystals can be described within the framework of Band transport.
-
electron spectroscopy of functional organic thin films deep insights into valence electronic structure in relation to charge transport property
Progress in Surface Science, 2008Co-Authors: Nobuo Ueno, Satoshi KeraAbstract:Abstract We summarize both historical and recent challenges on angle-resolved and high-energy resolution ultraviolet photoelectron spectroscopy (UPS) of organic thin films. Topics selected for this article are mainly on electron spectroscopic study of the electronic states in relation to charge mobility of organic molecular thin films, especially of weakly interacting organic molecular solids. We describe intramolecular Band Dispersion in a quasi-one-dimensional molecular chain and intermolecular Band Dispersion measured with angle-resolved UPS. The latter offers a spectroscopic estimation of the drift hole mobility in organic semiconductors. Furthermore we describe briefly hole-vibration coupling in organic ultrathin films, which dominates the hopping hole mobility and has been recently measured with high resolution UPS. These experiments are thus considered to be a kind of the first-principle measurement of the mobility of organic thin films, which have not yet been realized with electrical measurements. Conduction Band Dispersion studied with low-energy electron transmission, which is needed in analyzing angle-resolved UPS, ultrafast phenomena appearing in conventional UPS measurements and other interesting work are also introduced.
Satoshi Kera - One of the best experts on this subject based on the ideXlab platform.
-
accessing the conduction Band Dispersion in ch3nh3pbi3 single crystals
Journal of Physical Chemistry Letters, 2021Co-Authors: Jin-peng Yang, Nobuo Ueno, Hiroyuki Yoshida, Haruki Sato, Hibiki Orio, Xianjie Liu, Mats Fahlman, Takashi Yamada, Satoshi KeraAbstract:The conduction Band Dispersion in methylammonium lead iodide (CH3NH3PbI3) was studied by both angle-resolved two-photon photoelectron spectroscopy (AR-2PPE) with low photon intensity (∼0.0125 nJ/pulse) and angle-resolved low-energy inverse photoelectron spectroscopy (AR-LEIPS). Clear energy Dispersion of the conduction Band along the Γ-M direction was first observed by these independent methods under different temperatures, and the Dispersion was found to be consistent with Band calculation under the cubic phase. The effective mass of the electrons at the Γ point was estimated to be (0.20 ± 0.05)m0 at the temperature of 90 K. The observed conduction Band energy was different between the AR-LEIPS and AR-2PPE, which was ascribed to the electronic-correlation-dependent difference of initial and final states probing processes. The present results also indicate that the surface structure in CH3NH3PbI3 provides the cubic-dominated electronic property even at lower temperatures.
-
Accessing the conduction Band Dispersion in CH3NH3PbI3 single crystals.
arXiv: Materials Science, 2020Co-Authors: Jin-peng Yang, Nobuo Ueno, Hiroyuki Yoshida, Haruki Sato, Hibiki Orio, Xianjie Liu, Mats Fahlman, Takashi Yamada, Satoshi KeraAbstract:The conduction Band structure in methylammonium lead iodide (CH3NH3PbI3) was studied both by angle-resolved two-photon photoemission spectroscopy (AR-2PPE) with low-photon intensity and angle-resolved low-energy inverse photoelectron spectroscopy (AR-LEIPS). Clear energy Dispersion of the conduction Band along the {\Gamma}M direction was observed by these independent methods under different temperatures, and the Dispersion was found to be consistent with Band calculations under the cubic phase. The effective mass of the electrons at the {\Gamma} point was estimated to be (0.20+-0.05)m0 at 90 K. The observed energy position was largely different between the AR-LEIPS and AR-2PPE, demonstrating the electron correlation effects on the Band structures. The present results also indicate that the surface structure in CH3NH3PbI3 provides the cubic-dominated electronic property even at lower temperatures.
-
highest occupied molecular orbital Band Dispersion of rubrene single crystals as observed by angle resolved ultraviolet photoelectron spectroscopy
Physical Review Letters, 2010Co-Authors: Shin Ichi Machida, Nobuo Ueno, Steffen Duhm, Qian Xin, Satoshi Kera, Yasuo Nakayama, Akihiro Funakoshi, Naoki Ogawa, Hisao IshiiAbstract:The electronic structure of rubrene single crystals was studied by angle-resolved ultraviolet photoelectron spectroscopy. A clear energy Dispersion of the highest occupied molecular orbital-derived Band was observed, and the Dispersion width was found to be 0.4 eV along the well-stacked direction. The effective mass of the holes was estimated to be $0.65(\ifmmode\pm\else\textpm\fi{}0.1){m}_{0}$. The present results suggest that the carrier conduction mechanism in rubrene single crystals can be described within the framework of Band transport.
-
electron spectroscopy of functional organic thin films deep insights into valence electronic structure in relation to charge transport property
Progress in Surface Science, 2008Co-Authors: Nobuo Ueno, Satoshi KeraAbstract:Abstract We summarize both historical and recent challenges on angle-resolved and high-energy resolution ultraviolet photoelectron spectroscopy (UPS) of organic thin films. Topics selected for this article are mainly on electron spectroscopic study of the electronic states in relation to charge mobility of organic molecular thin films, especially of weakly interacting organic molecular solids. We describe intramolecular Band Dispersion in a quasi-one-dimensional molecular chain and intermolecular Band Dispersion measured with angle-resolved UPS. The latter offers a spectroscopic estimation of the drift hole mobility in organic semiconductors. Furthermore we describe briefly hole-vibration coupling in organic ultrathin films, which dominates the hopping hole mobility and has been recently measured with high resolution UPS. These experiments are thus considered to be a kind of the first-principle measurement of the mobility of organic thin films, which have not yet been realized with electrical measurements. Conduction Band Dispersion studied with low-energy electron transmission, which is needed in analyzing angle-resolved UPS, ultrafast phenomena appearing in conventional UPS measurements and other interesting work are also introduced.
-
origin of the highest occupied Band position in pentacene films from ultraviolet photoelectron spectroscopy hole stabilization versus Band Dispersion
Physical Review B, 2006Co-Authors: Hirohiko Fukagawa, Hiroyuki Yamane, Satoshi Kera, Takashi Kataoka, Masakazu Nakamura, Kazuhiro Kudo, Nobuo UenoAbstract:The electronic structure of pentacene/graphite, pentacene/Cu-phthalocyanine (CuPc)/graphite, and $\text{pentacene}∕\mathrm{Si}{\mathrm{O}}_{2}∕\mathrm{Si}(100)$ was studied by ultraviolet photoelectron spectroscopy as a function of the thickness of the pentacene film. We observed that the binding energy position of the highest occupied molecular orbital (HOMO) of pentacene becomes significantly lower on CuPc and $\mathrm{Si}{\mathrm{O}}_{2}$ surfaces than that on graphite. Furthermore, a splitting of the UPS Band was observed only for the HOMO of thicker crystalline films on CuPc and $\mathrm{Si}{\mathrm{O}}_{2}$ surfaces, where the molecules are oriented with their long axis nearly perpendicular to the substrate surface. The splitting is ascribed to the intermolecular Band Dispersion, and the decrease in the threshold ionization energy on CuPc and $\mathrm{Si}{\mathrm{O}}_{2}$ surfaces originates from the HOMO-Band Dispersion as well as the increase in the relaxation/polarization energies, which may be caused by the better molecular packing structure with a nearly standing molecular orientation.
Zhixiang Shi - One of the best experts on this subject based on the ideXlab platform.
-
observation of the anisotropic dirac cone in the Band Dispersion of 112 structured iron based superconductor ca0 9la0 1feas2
arXiv: Superconductivity, 2016Co-Authors: Zhiyong Liu, Xiangzhuo Xing, W Zhou, Yue Sun, C C Fan, Haifeng Yang, Jishan Liu, Qi Yao, Zhixiang ShiAbstract:CaFeAs2 is a parent compound of recently discovered 112-type iron-based superconductors. It is predicted to be a staggered intercalation compound that naturally integrates both quantum spin Hall insulating and superconducting layers and an ideal system for the realization of Majorana modes. We performed a systematical angle-resolved photoemission spectroscopy and first-principle calculation study of the slightly electron-doped CaFeAs2. We found that the zigzag As chain of 112-type iron-based superconductors play a considerable role in the low-energy electronic structure, resulting in the characteristic Dirac-cone like Band Dispersion as the prediction. Our experimental results further confirm that these Dirac cones only exists around the X but not Y points in the Brillouin zone, breaking the S4 symmetry at iron sites. Our findings present the compelling support to the theoretical prediction that the 112-type iron-based superconductors might host the topological nontrivial edge states. The slightly electron doped CaFeAs2 would provide us a unique opportunity to realize and explore Majorana fermion physics.
-
observation of the anisotropic dirac cone in the Band Dispersion of 112 structured iron based superconductor ca0 9la0 1feas2
Applied Physics Letters, 2016Co-Authors: Zhiyong Liu, Xiangzhuo Xing, W Zhou, Yue Sun, C C Fan, Haifeng Yang, Jishan Liu, Qi Yao, Zhixiang ShiAbstract:CaFeAs2 is a parent compound of recently discovered 112-type iron-based superconductors. It is predicted to be a staggered intercalation compound that naturally integrates both quantum spin Hall insulating and superconducting layers and an ideal system for the realization of Majorana modes. We performed a systematical angle-resolved photoemission spectroscopy and first-principles calculation study of the slightly electron-doped CaFeAs2. We found that the zigzag As chain of 112-type iron-based superconductors play a considerable role in the low-energy electronic structure, resulting in the characteristic Dirac-cone like Band Dispersion as the prediction. Our experimental results further confirm that these Dirac cones only exist around the X but not Y points in the Brillouin zone, breaking the S4 symmetry at iron sites. Our findings present the compelling support to the theoretical prediction that the 112-type iron-based superconductors might host the topological nontrivial edge states. The slightly electro...
Caio H Lewenkopf - One of the best experts on this subject based on the ideXlab platform.
-
tight binding model for the Band Dispersion in rhombohedral topological insulators over the whole brillouin zone
Physical Review B, 2018Co-Authors: Carlos Mera Acosta, Matheus P Lima, Antonio J R Da Silva, A Fazzio, Caio H LewenkopfAbstract:We put forward a tight-binding model for rhombohedral topological insulators materials with the space group $D^{5}_{3d}(R\bar{3}m)$. The model describes the bulk Band structure of these materials over the whole Brillouin zone. Within this framework, we also describe the topological nature of surface states, characterized by a Dirac cone-like Dispersion and the emergence of surface projected bulk states near to the Dirac-point in energy. We find that the breaking of the $R_{3}$ symmetry as one moves away from the $\Gamma$ point has an important role in the hybridization of the $p_x$, $p_y$, and $p_z$ atomic orbitals. In our tight-binding model, the latter leads to a Band mixing matrix element ruled by a single parameter. We show that our model gives a good description of the strategies/mechanisms proposed in the literature to eliminate and/or energy shift the bulk states away from the Dirac point, such as stacking faults and the introduction of an external applied electric field.
-
tight binding model for the Band Dispersion in rhombohedral topological insulators over the whole brillouin zone
Physical Review B, 2018Co-Authors: Carlos Mera Acosta, Matheus P Lima, Antonio J R Da Silva, A Fazzio, Caio H LewenkopfAbstract:We put forward a tight-binding model for rhombohedral topological insulator materials with the space group ${D}_{3d}^{5}(R\overline{3}m)$. The model describes the bulk Band structure of these materials over the whole Brillouin zone. Within this framework, we also describe the topological nature of surface states, characterized by a Dirac conelike Dispersion and the emergence of surface projected bulk states near to the Dirac point in energy. We find that the breaking of the ${R}_{3}$ symmetry as one moves away from the $\mathrm{\ensuremath{\Gamma}}$ point has an important role in the hybridization of the ${p}_{x}, {p}_{y}$, and ${p}_{z}$ atomic orbitals. In our tight-binding model, the latter leads to a Band mixing matrix element ruled by a single parameter. We show that our model gives a good description of the strategies/mechanisms proposed in the literature to eliminate and/or energy shift the bulk states away from the Dirac point, such as stacking faults and the introduction of an external applied electric field.
Qi Yao - One of the best experts on this subject based on the ideXlab platform.
-
observation of the anisotropic dirac cone in the Band Dispersion of 112 structured iron based superconductor ca0 9la0 1feas2
arXiv: Superconductivity, 2016Co-Authors: Zhiyong Liu, Xiangzhuo Xing, W Zhou, Yue Sun, C C Fan, Haifeng Yang, Jishan Liu, Qi Yao, Zhixiang ShiAbstract:CaFeAs2 is a parent compound of recently discovered 112-type iron-based superconductors. It is predicted to be a staggered intercalation compound that naturally integrates both quantum spin Hall insulating and superconducting layers and an ideal system for the realization of Majorana modes. We performed a systematical angle-resolved photoemission spectroscopy and first-principle calculation study of the slightly electron-doped CaFeAs2. We found that the zigzag As chain of 112-type iron-based superconductors play a considerable role in the low-energy electronic structure, resulting in the characteristic Dirac-cone like Band Dispersion as the prediction. Our experimental results further confirm that these Dirac cones only exists around the X but not Y points in the Brillouin zone, breaking the S4 symmetry at iron sites. Our findings present the compelling support to the theoretical prediction that the 112-type iron-based superconductors might host the topological nontrivial edge states. The slightly electron doped CaFeAs2 would provide us a unique opportunity to realize and explore Majorana fermion physics.
-
observation of the anisotropic dirac cone in the Band Dispersion of 112 structured iron based superconductor ca0 9la0 1feas2
Applied Physics Letters, 2016Co-Authors: Zhiyong Liu, Xiangzhuo Xing, W Zhou, Yue Sun, C C Fan, Haifeng Yang, Jishan Liu, Qi Yao, Zhixiang ShiAbstract:CaFeAs2 is a parent compound of recently discovered 112-type iron-based superconductors. It is predicted to be a staggered intercalation compound that naturally integrates both quantum spin Hall insulating and superconducting layers and an ideal system for the realization of Majorana modes. We performed a systematical angle-resolved photoemission spectroscopy and first-principles calculation study of the slightly electron-doped CaFeAs2. We found that the zigzag As chain of 112-type iron-based superconductors play a considerable role in the low-energy electronic structure, resulting in the characteristic Dirac-cone like Band Dispersion as the prediction. Our experimental results further confirm that these Dirac cones only exist around the X but not Y points in the Brillouin zone, breaking the S4 symmetry at iron sites. Our findings present the compelling support to the theoretical prediction that the 112-type iron-based superconductors might host the topological nontrivial edge states. The slightly electro...
