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Revealing time characteristics of optical excitations in dielectric and plasmonic structures through cathodoluminescence interferometry
Authors:
Evelijn Akerboom,
Hirohsi Sugimoto,
Minoru Fujii,
Nicolas Pazos-Perez,
Ramon A. Álvarez Puebla,
A. Femius Koenderink,
F. Javier García de Abajo,
Albert Polman
Abstract:
Cathodoluminescence (CL) spectroscopy provides access to optical excitations with nanometer spatial resolution, but direct time-resolved measurements of optical resonances remain challenging. Here, we demonstrate that CL interferometry provides access to the temporal response, phase behavior, and modal spectral structure of resonant nanoscale scatterers without requiring ultrafast pump-probe schem…
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Cathodoluminescence (CL) spectroscopy provides access to optical excitations with nanometer spatial resolution, but direct time-resolved measurements of optical resonances remain challenging. Here, we demonstrate that CL interferometry provides access to the temporal response, phase behavior, and modal spectral structure of resonant nanoscale scatterers without requiring ultrafast pump-probe schemes. We develop an analytical framework in which Fourier transformation angle- and frequency-resolved CL interferograms yields the decay time of optical resonances governed by the linear optical response. Multimode resonators exhibit characteristic temporal CL beating signatures associated with spectral mode splitting. By exploiting transition radiation emitted from a nearby metallic surface as a broadband reference, we further demonstrate phase retrieval and cross-correlation measurements between instantaneous and resonant emission processes. Experimental measurements on Au nanoparticles, broadband plasmonic emitters, Au nanostars, and Si nanospheres supporting multipolar Mie resonances confirm the theoretical predictions, and decay times in the range 1-10 fs are derived for each system. Our results establish CL interferometry as a powerful approach for accessing spectral, spatial, and phase information within a single nanoscale measurement with fs resolution.
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Submitted 11 August, 2026;
originally announced August 2026.
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Polymer-Shell Coating of Mie-Resonant Silicon Nanospheres for Controlled Fabrication of Self-Assembled Monolayer
Authors:
Oanh Vu,
Jialu Song,
Hiroshi Sugimoto,
Minoru Fujii
Abstract:
A polymer shell offers a unique opportunity to tailor structural and optical properties of optically functional nanoparticles and their ensembles. Here, we develop a process to coat Mie-resonant silicon nanospheres (Si NSs) with a thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) hydrogel shell. We show formation of a PNIPAM shell of controlled thickness from the change of the hydrodynamic dia…
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A polymer shell offers a unique opportunity to tailor structural and optical properties of optically functional nanoparticles and their ensembles. Here, we develop a process to coat Mie-resonant silicon nanospheres (Si NSs) with a thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) hydrogel shell. We show formation of a PNIPAM shell of controlled thickness from the change of the hydrodynamic diameter and study the effect of thermoresponsive shrinkage and expansion of the shell on the Mie resonance of a Si NS. We then demonstrate that Si NSs with PNIPAM shells enable fabrication of cluster-free, self-assembled monolayers of Si NSs, in which distances between NSs are controlled by the PNIPAM shell thickness.
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Submitted 9 May, 2025;
originally announced May 2025.
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Routing Light Emission from Monolayer MoS$_2$ by Mie Resonances of Crystalline Silicon Nanospheres
Authors:
Keisuke Ozawa,
Hiroshi Sugimoto,
Daisuke Shima,
Tatsuki Hinamoto,
Mojtaba Karimi Habil,
Yan Joe Lee,
Søren Raza,
Keisuke Imaeda,
Kosei Ueno,
Mark L. Brongersma,
Minoru Fujii
Abstract:
A dielectric Mie-resonant nanoantenna is capable of controlling the directionality of the emission from nearby quantum emitters through the excitation of multiple degenerate Mie resonances. A crystalline silicon nanosphere (Si NS) is a promising candidate for a dielectric nanoantenna because crystalline Si has a large refractive index (3.8 at 650 nm) and the small imaginary part of a complex refra…
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A dielectric Mie-resonant nanoantenna is capable of controlling the directionality of the emission from nearby quantum emitters through the excitation of multiple degenerate Mie resonances. A crystalline silicon nanosphere (Si NS) is a promising candidate for a dielectric nanoantenna because crystalline Si has a large refractive index (3.8 at 650 nm) and the small imaginary part of a complex refractive index (0.015 at 650 nm) as an optical material. In this work, we control the emission directionality of excitons supported by monolayer transition metal dichalcogenides (1L-TMDCs) using a Si NS. We first discuss the condition to extract the emission preferentially towards the Si NS side from the analytical calculations. We then study the photoluminescence (PL) of 1L-TMDCs on which differently sized single Si NSs are placed. We show that the PL spectral shape strongly depends on the emission direction, and that the emission toward the Si NS side (top) with respect to the opposite side (bottom) is the largest at wavelengths between the magnetic dipole and electric dipole Mie resonances of a Si NS. Finally, we quantitatively discuss the spectral shape of the top-to-bottom ratio from numerical simulations.
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Submitted 28 October, 2024;
originally announced October 2024.
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Covariance Linkage Assimilation method for Unobserved Data Exploration
Authors:
Yosuke Harashima,
Takashi Miyake,
Ryuto Baba,
Tomoaki Takayama,
Shogo Takasuka,
Yasuteru Shigeta,
Yuichi Yamaguchi,
Akihiko Kudo,
Mikiya Fujii
Abstract:
This study proposes a materials search method combining a data assimilation technique based on a multivariate Gaussian distribution with Bayesian optimization. The efficiency of the search using this method was demonstrated using a pair of example functions. By combining Bayesian optimization with the data assimilation technique, the maximum value of the example function was found more efficiently…
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This study proposes a materials search method combining a data assimilation technique based on a multivariate Gaussian distribution with Bayesian optimization. The efficiency of the search using this method was demonstrated using a pair of example functions. By combining Bayesian optimization with the data assimilation technique, the maximum value of the example function was found more efficiently compared to ordinary Bayesian optimization without the data assimilation. A practical demonstration was also conducted by constructing a data assimilation model for the bandgap of (Sr$_{1-x_{1}-x_{2}}$La$_{x_{1}}$Na$_{x_{2}}$)(Ti$_{1-x_{1}-x_{2}}$Ga$_{x_{1}}$Ta$_{x_{2}}$)O$_{3}$. The concentration dependence of the bandgap was analyzed, and synthesis was performed with chemical compositions in the sparse region of the training data points to validate the predictions.
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Submitted 15 July, 2025; v1 submitted 16 August, 2024;
originally announced August 2024.
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Universal click-chemistry approach for the DNA functionalization of nanoparticles
Authors:
Nicole Siegel,
Hiroaki Hasebe,
German Chiarelli,
Denis Garoli,
Hiroshi Sugimoto,
Minoru Fujii,
Guillermo P. Acuna,
Karol Kolataj
Abstract:
Nanotechnology has revolutionized the fabrication of hybrid species with tailored functionalities. A milestone in this field is the DNA conjugation of nanoparticles, introduced almost 30 years ago, which typically exploits the affinity between thiol groups and metallic surfaces. Over the last decades, developments in colloidal research have enabled the synthesis of an assortment of non-metallic st…
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Nanotechnology has revolutionized the fabrication of hybrid species with tailored functionalities. A milestone in this field is the DNA conjugation of nanoparticles, introduced almost 30 years ago, which typically exploits the affinity between thiol groups and metallic surfaces. Over the last decades, developments in colloidal research have enabled the synthesis of an assortment of non-metallic structures, such as high-index dielectric nanoparticles, with unique properties not previously accessible with traditional metallic nanoparticles. However, to stabilize, integrate and provide further functionality to non-metallic nanoparticles, reliable techniques for their functionalization with DNA will be crucial. Here, we combine well-established dibenzylcyclooctyne-azide click-chemistry with a simple freeze-thaw method to achieve the functionalization of silica and silicon nanoparticles, which form exceptionally stable colloids with a high DNA surface density of 0.2 molecules/nm2. Furthermore, we demonstrate that these functionalized colloids can be self-assembled into high-index dielectric optical antennas with a yield of up to 78% via the use of DNA origami. Finally, we extend this method to functionalize other important nanomaterials, including oxides, polymers, core-shell and metal nanostructures. Our results indicate that the method presented herein serves as a crucial complement to conventional thiol functionalization chemistry and thus greatly expands the toolbox of DNA-functionalized nanoparticles currently available.
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Submitted 29 December, 2023; v1 submitted 27 September, 2023;
originally announced September 2023.
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Ultraviolet Mie resonances in computationally discovered boron phosphide nanoparticles
Authors:
Mark Kamper Svendsen,
Hiroshi Sugimoto,
Artyom Assadillayev,
Daisuke Shima,
Minoru Fujii,
Kristian Sommer Thygesen,
Søren Raza
Abstract:
Controlling ultraviolet light at the nanoscale using optical Mie resonances holds great promise for a diverse set of applications, such as lithography, sterilization, and biospectroscopy. However, Mie resonances hosted by dielectric nanoantennas are difficult to realize at ultraviolet wavelengths due to the lack of both suitable materials and fabrication methods. Here, we systematically search for…
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Controlling ultraviolet light at the nanoscale using optical Mie resonances holds great promise for a diverse set of applications, such as lithography, sterilization, and biospectroscopy. However, Mie resonances hosted by dielectric nanoantennas are difficult to realize at ultraviolet wavelengths due to the lack of both suitable materials and fabrication methods. Here, we systematically search for improved materials by computing the frequency dependent optical permittivity of 338 binary semiconductors and insulators from first principles, and evaluate their potential performance as high refractive index materials using Mie theory. Our analysis reveals several interesting candidate materials among which boron phosphide (BP) appears particularly promising. We then prepare BP nanoparticles and demonstrate that they support Mie resonances at visible and ultraviolet wavelengths using both far-field optical measurements and near-field electron energy-loss spectroscopy. We also present a laser reshaping method to realize spherical Mie-resonant BP nanoparticles. With a refractive index above 3 and low absorption losses, BP nanostructures advance Mie optics to the ultraviolet.
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Submitted 27 December, 2021;
originally announced December 2021.
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Disentangling cathodoluminescence spectra in nanophotonics: particle eigenmodes vs transition radiation
Authors:
Saskia Fiedler,
P. Elli Stamatopoulou,
Artyom Assadillayev,
Christian Wolff,
Hiroshi Sugimoto,
Minoru Fujii,
N. Asger Mortensen,
Søren Raza,
Christos Tserkezis
Abstract:
Cathodoluminescence spectroscopy performed in an electron microscope has proven a versatile tool for analysing the near- and far-field optical response of plasmonic and dielectric nanostructures. Nevertheless, the transition radiation produced by electron impact is often disregarded in the interpretation of the spectra recorded from resonant nanoparticles. Here we show, experimentally and theoreti…
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Cathodoluminescence spectroscopy performed in an electron microscope has proven a versatile tool for analysing the near- and far-field optical response of plasmonic and dielectric nanostructures. Nevertheless, the transition radiation produced by electron impact is often disregarded in the interpretation of the spectra recorded from resonant nanoparticles. Here we show, experimentally and theoretically, that transition radiation can by itself generate distinct resonances which, depending on the time of flight of the electron beam inside the particle, can result from constructive or destructive interference in time. Superimposed on the eigenmodes of the investigated structures, these resonances can distort the recorded spectrum and lead to potentially erroneous assignment of modal characters to the spectral features. We develop an intuitive analogy that helps distinguish between the two contributions. As an example, we focus on the case of silicon nanospheres, and show that our analysis facilitates the unambiguous interpretation of experimental measurements on Mie-resonant nanoparticles.
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Submitted 14 March, 2022; v1 submitted 9 December, 2021;
originally announced December 2021.
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Deep variational quantum eigensolver for excited states and its application to quantum chemistry calculation of periodic materials
Authors:
Kaoru Mizuta,
Mikiya Fujii,
Shigeki Fujii,
Kazuhide Ichikawa,
Yutaka Imamura,
Yukihiro Okuno,
Yuya O. Nakagawa
Abstract:
A programmable quantum device that has a large number of qubits without fault-tolerance has emerged recently. Variational Quantum Eigensolver (VQE) is one of the most promising ways to utilize the computational power of such devices to solve problems in condensed matter physics and quantum chemistry. As the size of the current quantum devices is still not large for rivaling classical computers at…
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A programmable quantum device that has a large number of qubits without fault-tolerance has emerged recently. Variational Quantum Eigensolver (VQE) is one of the most promising ways to utilize the computational power of such devices to solve problems in condensed matter physics and quantum chemistry. As the size of the current quantum devices is still not large for rivaling classical computers at solving practical problems, Fujii et al. proposed a method called "Deep VQE" which can provide the ground state of a given quantum system with the smaller number of qubits by combining the VQE and the technique of coarse-graining [K. Fujii, et al, arXiv:2007.10917]. In this paper, we extend the original proposal of Deep VQE to obtain the excited states and apply it to quantum chemistry calculation of a periodic material, which is one of the most impactful applications of the VQE. We first propose a modified scheme to construct quantum states for coarse-graining in Deep VQE to obtain the excited states. We also present a method to avoid a problem of meaningless eigenvalues in the original Deep VQE without restricting variational quantum states. Finally, we classically simulate our modified Deep VQE for quantum chemistry calculation of a periodic hydrogen chain as a typical periodic material. Our method reproduces the ground-state energy and the first-excited-state energy with the errors up to O(1)% despite the decrease in the number of qubits required for the calculation by two or four compared with the naive VQE. Our result will serve as a beacon for tackling quantum chemistry problems with classically-intractable sizes by smaller quantum devices in the near future.
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Submitted 26 August, 2021; v1 submitted 1 April, 2021;
originally announced April 2021.
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MENP: An Open-Source MATLAB Implementation of Multipole Expansion for Applications in Nanophotonics
Authors:
Tatsuki Hinamoto,
Minoru Fujii
Abstract:
In modern nanophotonics, multipolar interference plays an indispensable role to realize novel optical devices represented by metasurfaces with unprecedented functionalities. Not only to engineer sub-wavelength structures that constitute such devices but also to realize and interpret unnatural phenomena in nanophotonics, a program that efficiently carries out multipole expansion is highly demanded.…
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In modern nanophotonics, multipolar interference plays an indispensable role to realize novel optical devices represented by metasurfaces with unprecedented functionalities. Not only to engineer sub-wavelength structures that constitute such devices but also to realize and interpret unnatural phenomena in nanophotonics, a program that efficiently carries out multipole expansion is highly demanded. MENP is a MATLAB program for computation of multipole contributions to light scattering from current density distributions induced in nanophotonic resonators. The main purpose of MENP is to carry out post-processing of a rigid multipole expansion for full-field simulations which in principle provide the information of all near- and far-field interactions (e.g. as a total scattering cross section). MENP decomposes total scattering cross sections into partial ones due to electric and magnetic dipoles and higher-order terms based on recently developed exact multipole expansion formulas. We validate the program by comparing results for ideal and realistic nanospheres with those obtained with the Mie theory. We also demonstrate the potential of MENP for analysis of anapole states by calculating the multipole expansion under the long-wavelength approximation which enables us to introduce toroidal dipole moments.
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Submitted 6 November, 2020;
originally announced November 2020.
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Spontaneous organizations of diverse network structures in coupled logistic maps with a delayed connection change
Authors:
Amika Ohara,
Masashi Fujii,
Akinori Awazu
Abstract:
In this study, we performed comprehensive morphological investigations of the spontaneous formations of effective network structures among elements in coupled logistic maps, specifically with a delayed connection change. Our proposed model showed ten states with different structural and dynamic features of the network topologies. Based on the parameter values, various stable networks, such as hier…
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In this study, we performed comprehensive morphological investigations of the spontaneous formations of effective network structures among elements in coupled logistic maps, specifically with a delayed connection change. Our proposed model showed ten states with different structural and dynamic features of the network topologies. Based on the parameter values, various stable networks, such as hierarchal networks with pacemakers or multiple layers, and a loop-shaped network were found. We also found various dynamic networks with temporal changes in the connections, which involved hidden network structures. Furthermore, we found that the shapes of the formed network structures were highly correlated to the dynamic features of the constituent elements. The present results provide diverse insights into the dynamics of neural networks and various other biological and social networks.
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Submitted 18 August, 2020;
originally announced August 2020.
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Study of Deep Generative Models for Inorganic Chemical Compositions
Authors:
Yoshihide Sawada,
Koji Morikawa,
Mikiya Fujii
Abstract:
Generative models based on generative adversarial networks (GANs) and variational autoencoders (VAEs) have been widely studied in the fields of image generation, speech generation, and drug discovery, but, only a few studies have focused on the generation of inorganic materials. Such studies use the crystal structures of materials, but material researchers rarely store this information. Thus, we g…
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Generative models based on generative adversarial networks (GANs) and variational autoencoders (VAEs) have been widely studied in the fields of image generation, speech generation, and drug discovery, but, only a few studies have focused on the generation of inorganic materials. Such studies use the crystal structures of materials, but material researchers rarely store this information. Thus, we generate chemical compositions without using crystal information. We use a conditional VAE (CondVAE) and a conditional GAN (CondGAN) and show that CondGAN using the bag-of-atom representation with physical descriptors generates better compositions than other generative models. Also, we evaluate the effectiveness of the Metropolis-Hastings-based atomic valency modification and the extrapolation performance, which is important to material discovery.
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Submitted 24 October, 2019;
originally announced October 2019.
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Determination of the local structure of Sr$_{2-x}$M$_x$IrO$_4$ (M = K, La) as a function of doping and temperature
Authors:
K. Terashima,
E. Paris,
E. Salas-Colera,
L. Simonelli,
B. Joseph,
T. Wakita,
K. Horigane,
M. Fujii,
K. Kobayashi,
R. Horie,
J. Akimitsu,
Y. Muraoka,
T. Yokoya,
N. L. Saini
Abstract:
The local structure of correlated spin-orbit insulator Sr$_{2-x}$M$_x$IrO$_4$ (M = K, La) has been investigated by Ir L$_3$-edge extended x-ray absorption fine structure measurements. The measurements were performed as a function of temperature for different dopings induced by substitution of Sr with La or K. It is found that Ir-O bonds have strong covalency and they hardly show any change across…
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The local structure of correlated spin-orbit insulator Sr$_{2-x}$M$_x$IrO$_4$ (M = K, La) has been investigated by Ir L$_3$-edge extended x-ray absorption fine structure measurements. The measurements were performed as a function of temperature for different dopings induced by substitution of Sr with La or K. It is found that Ir-O bonds have strong covalency and they hardly show any change across the Néel temperature. In the studied doping range, neither Ir-O bonds nor their dynamics, measured by their mean square relative displacements, show any appreciable change upon carrier doping, indicating possibility of a nanoscale phase separation in the doped system. On the other hand, there is a large increase of the static disorder in Ir-Sr correlation, larger for K doping than La doping. Similarities and differences with respect to the local lattice displacements in cuprates are briefly discussed.
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Submitted 1 October, 2018;
originally announced October 2018.
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Evolution of remnant Fermi surface state in lightly-doped correlated spin-orbit insulator Sr$_{2-x}$La$_x$IrO$_4$
Authors:
K. Terashima,
M. Sunagawa,
H. Fujiwara,
T. Fukura,
M. Fujii,
K. Okada,
K. Horigane,
K. Kobayashi,
R. Horie,
J. Akimitsu,
E. Golias,
D. Marchenko,
A. Varykhalov,
N. L. Saini,
T. Wakita,
Y. Muraoka,
T. Yokoya
Abstract:
Electronic structure has been studied in lightly electron doped correlated spin-orbit insulator Sr$_2$IrO$_4$ by angle-resolved photoelectron spectroscopy. We have observed coexistence of the lower Hubbard band and the in-gap band, the momentum dependence of the latter traces that of the band calculations without on-site Coulomb repulsion. The in-gap state remained anisotropically gapped in all ob…
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Electronic structure has been studied in lightly electron doped correlated spin-orbit insulator Sr$_2$IrO$_4$ by angle-resolved photoelectron spectroscopy. We have observed coexistence of the lower Hubbard band and the in-gap band, the momentum dependence of the latter traces that of the band calculations without on-site Coulomb repulsion. The in-gap state remained anisotropically gapped in all observed momentum area, forming a remnant Fermi surface state, evolving towards the Fermi energy by carrier doping. These experimental results show a striking similarity with those observed in deeply underdoped cuprates, suggesting the common nature of the nodal liquid states observed in both compounds.
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Submitted 24 June, 2017;
originally announced June 2017.
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Phenomenological theory of optical broadening in zero-dimensional systems applied to silicon nanocrystals
Authors:
V. V. Nikolaev,
N. S. Averkiev,
Minoru Fujii
Abstract:
We develop a phenomenological theory of inhomogeneous broadening in zero-dimensional systems and apply it to study photoluminescence (PL) spectra of silicon nanocrystals measured at helium and room temperatures. The proposed approach allowed us to explain experimentally observed PL peak asymmetry, linear dependence of the peak width on its maximum and anomalous alteration of spectral characteristi…
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We develop a phenomenological theory of inhomogeneous broadening in zero-dimensional systems and apply it to study photoluminescence (PL) spectra of silicon nanocrystals measured at helium and room temperatures. The proposed approach allowed us to explain experimentally observed PL peak asymmetry, linear dependence of the peak width on its maximum and anomalous alteration of spectral characteristics with temperature increase.
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Submitted 5 April, 2016;
originally announced April 2016.
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Near-infrared photoluminescence from molecular crystals containing tellurium
Authors:
Hong-Tao Sun,
Yoshio Sakka,
Naoto Shirahata,
Minoru Fujii,
Tetsu Yonezawa
Abstract:
We report the observation of near-infrared photoluminescence from Te4(Ga2Cl7)2 and Te4(Al2Cl7)2 molecular crystals containing Te42+ polycations. The experimental and theoretical results clearly revealed that Te42+ polycation is one smart near-infrared emitter with characteristic emission peaks at 1252 and 1258 nm for Te4(Ga2Cl7)2 and Te4(Al2Cl7)2 crystals, respectively, resulting from the intrinsi…
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We report the observation of near-infrared photoluminescence from Te4(Ga2Cl7)2 and Te4(Al2Cl7)2 molecular crystals containing Te42+ polycations. The experimental and theoretical results clearly revealed that Te42+ polycation is one smart near-infrared emitter with characteristic emission peaks at 1252 and 1258 nm for Te4(Ga2Cl7)2 and Te4(Al2Cl7)2 crystals, respectively, resulting from the intrinsic electronic transitions of Te42+. Furthermore, it was also found that the emissions strongly depend on the excitation wavelengths for both Te4(Ga2Cl7)2 and Te4(Al2Cl7)2 samples, most possibly owing to the co-existence of other Te-related optically active centers. This research not only enriches the species of luminescent charged p-block element polyhedra and deepens the understanding of Te-related photophysical behaviors, but also may stimulate efforts for designing novel material systems using such active centers. It is also greatly expected that these sub-nanometer optically active species could exist in other systems such as glasses, polymers, and bulk optical crystals, and the stabilization of these centers in widely used hosts will pave the way for their practical applications.
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Submitted 6 September, 2012;
originally announced September 2012.
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Photoluminescence from Bi5(GaCl4)3 molecular crystal
Authors:
Hong-Tao Sun,
Beibei Xu,
Tetsu Yonezawa,
Yoshio Sakka,
Naoto Shirahata,
Minoru Fujii,
Jianrong Qiu,
Hong Gao
Abstract:
Bi5(GaCl4)3 sample has been synthesized through the oxidation of Bi metal by gallium chloride (GaCl3) salt. Powder X-ray diffraction as well as micro-Raman scattering results revealed that, in addition to crystalline Bi5(GaCl4)3 in the product, amorphous phase containing [GaCl4]- and [Ga2Cl7]- units also exist. The thorough comparison of steady-state and time-resolved photoluminescent behaviors be…
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Bi5(GaCl4)3 sample has been synthesized through the oxidation of Bi metal by gallium chloride (GaCl3) salt. Powder X-ray diffraction as well as micro-Raman scattering results revealed that, in addition to crystalline Bi5(GaCl4)3 in the product, amorphous phase containing [GaCl4]- and [Ga2Cl7]- units also exist. The thorough comparison of steady-state and time-resolved photoluminescent behaviors between Bi5(GaCl4)3 product and Bi5(AlCl4)3 crystal leads us to conclude that Bi53+ is the dominant emitter in the product, which gives rise to the ultrabroad emission ranging from 1 to 2.7 micrometer. Detailed quantum chemistry calculation helps us assign the observed excitations to some electronic transitions of Bi53+ polycation, especially at shorter wavelengths. It is believed that our work shown here not only is helpful to solve the confusions on the luminescent origin of bismuth in other material systems, but also serves to develop novel broadband tunable laser materials.
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Submitted 6 September, 2012; v1 submitted 31 May, 2012;
originally announced May 2012.
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Ultra-broad near-infrared photoluminescence from crystalline (K-crypt)2Bi2 containing [Bi2]2- dimers
Authors:
Hong-Tao Sun,
Tetsu Yonezawa,
Miriam M. Gillett-Kunnath,
Yoshio Sakka,
Naoto Shirahata,
Sa Chu Rong Gui,
Minoru Fujii,
Slavi C. Sevov
Abstract:
For the first time, we report that a single crystal of (K-crypt)2Bi2 containing [Bi2]2+ displays ultra-broad near-infrared photoluminescence (PL) peaking at around 1190 nm and having a full width at the half maximum of 212 nm, stemming from the inherent electronic transitions of [Bi2]2+.The results not only add to the number of charged Bi species with luminescence, but also deepen the understandin…
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For the first time, we report that a single crystal of (K-crypt)2Bi2 containing [Bi2]2+ displays ultra-broad near-infrared photoluminescence (PL) peaking at around 1190 nm and having a full width at the half maximum of 212 nm, stemming from the inherent electronic transitions of [Bi2]2+.The results not only add to the number of charged Bi species with luminescence, but also deepen the understanding of Bi-related near-infrared emission behavior and lead to the reconsideration of the fundamentally important issue of Bi-related PL mechanisms in some material systems such as bulk glasses, fibers, and conventional optical crystals.
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Submitted 12 September, 2012; v1 submitted 28 May, 2012;
originally announced May 2012.
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Energy transfer processes in Er-doped SiO2 sensitized with Si nanocrystals
Authors:
I. Izeddin,
D. Timmerman,
T. Gregorkiewicz,
A. S. Moskalenko,
A. A. Prokofiev,
I. N. Yassievich,
M. Fujii
Abstract:
We present a high-resolution photoluminescence study of Er-doped SiO2 sensitized with Si nanocrystals (Si NCs). Emission bands originating from recombination of excitons confined in Si NCs and of internal transitions within the 4f-electron core of Er3+ ions, and a band centered at lambda = 1200nm have been identified. Their kinetics have been investigated in detail. Based on these measurements,…
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We present a high-resolution photoluminescence study of Er-doped SiO2 sensitized with Si nanocrystals (Si NCs). Emission bands originating from recombination of excitons confined in Si NCs and of internal transitions within the 4f-electron core of Er3+ ions, and a band centered at lambda = 1200nm have been identified. Their kinetics have been investigated in detail. Based on these measurements, we present a comprehensive model for energy transfer mechanisms responsible for light generation in this system. A unique picture of energy flow between subsystems of Er3+ and Si NCs is developed, yielding truly microscopic information on the sensitization effect and its limitations. In particular, we show that most of the Er3+ ions available in the system are participating in the energy exchange. The long standing problem of apparent loss of optical activity of majority of Er dopants upon sensitization with Si NCs is clarified and assigned to appearance of a very efficient energy exchange mechanism between Si NCs and Er3+ ions. Application potential of SiO2:Er sensitized by Si NCs is discussed in view of the newly acquired microscopic insight.
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Submitted 5 June, 2008;
originally announced June 2008.
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Raman scattering by electron-hole excitations in silver nanocrystals
Authors:
H. Portales,
E. Duval,
L. Saviot,
M. Fujii,
M. Sumitomo,
S. Hayashi
Abstract:
Raman scattering experiments from silver nanocrystals embedded in films of amorphous silica are reported. In addition to the low-frequency peak due to vibrational quadrupolar modes, a broadband is observed in the high-frequency range, with a maximum at about 1000 $cm^{-1}$. The linear dependence of the position of this maximum on the inverse cluster radius is in agreement with the Raman scatteri…
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Raman scattering experiments from silver nanocrystals embedded in films of amorphous silica are reported. In addition to the low-frequency peak due to vibrational quadrupolar modes, a broadband is observed in the high-frequency range, with a maximum at about 1000 $cm^{-1}$. The linear dependence of the position of this maximum on the inverse cluster radius is in agreement with the Raman scattering by single or collective electron-hole excitations.
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Submitted 31 January, 2001;
originally announced January 2001.
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Magnetic and Critical Properties of Alternating Spin Chain with S=1/2,1 in Magnetic Fields
Authors:
Mitsuru Fujii,
Satoshi Fujimoto,
Norio Kawakami
Abstract:
We study an integrable spin chain with an alternating array of spins S=1/2, 1 in external magnetic fields using the Bethe ansatz exact solution. The calculated magnetization possesses a cusp structure at a critical magnetic field H=H_{C}, at which the specific heat shows a divergence property. We also calculate finite-size corrections to the energy spectrum, and obtain the critical exponents of…
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We study an integrable spin chain with an alternating array of spins S=1/2, 1 in external magnetic fields using the Bethe ansatz exact solution. The calculated magnetization possesses a cusp structure at a critical magnetic field H=H_{C}, at which the specific heat shows a divergence property. We also calculate finite-size corrections to the energy spectrum, and obtain the critical exponents of correlation functions with the use of conformal field theory (CFT). Low-energy properties of the model are described by two c=1 U(1) CFTs in H<H_{C} and one c=1 U(1) CFT in H>H_{C}.
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Submitted 4 November, 1996;
originally announced November 1996.