The University of Tokyo · Materials Science
Professor Masahiro Sato's research lab specializes in theoretical and computational materials science, focusing on charge transport mechanisms in organic and polymer-based semiconductors. The lab investigates quantum phenomena such as Kondo and Fano effects in low-dimensional nanostructures, as well as the dynamics of charge carriers and streamers in dielectric materials like polyethylene and silicone gel. Using multi-scale simulation techniques—combining first-principles calculations, molecular dynamics, and kinetic Monte Carlo methods—the lab aims to predict macroscopic electrical behavior from microscopic electronic and structural properties without relying on empirical models. Their work bridges fundamental physics with practical applications in power electronics and organic electronics.
Figures are computed from collected data and may differ slightly.
We have observed the Fano-Kondo antiresonance in a quantum wire with a side-coupled quantum dot. In a weak coupling regime, dips due to the Fano effect appeared. As the coupling strength increased, conductance in the regions between the dips decreased alternately. From the temperature dependence and the response to the magnetic field, we conclude that the conductance reduction is due to the Fano-Kondo antiresonance. At a Kondo valley with the Fano parameter q approximately 0, the phase shift is
AlN substrate is widely used along with silicone gel to encapsulate power electronic circuits. It is known that the weakness of the insulation system is surface discharges propagating at the gel-substrate interface. In this research, the nature of surface discharges in gel, on various substrates was investigated. The results are as follows: the maximum stopping length of cavities on AlN substrate was more than twice than that on other substrates, and light emission due to discharges in cavities
Silicone gel is widely used to encapsulate power electronic circuits. It is known that the weakness of this insulation system is the surface discharges between gel and substrate. These discharges give rise to the growth of cavities in gel, which may lead to eventual failure of the insulation. Despite the fact, surface discharges in gel has not yet been studied enough. In order to clarify the nature of streamers in the cavity and relation between streamer propagation and charge accumulation at th
This review highlights the updated picture of charge transport in polymer dielectrics and offers suggestions for future research. It begins with the backgrounds of the various theoretical charge transport models and the underlying concepts of the physical quantities. The techniques for deriving the microscopic physical quantities, e.g., the Marcus parameters and the spectral density of bath, from first-principles methods are outlined for tutorial purposes. Our recent multi-scale simulation studi
Hole mobility in crystalline polyethylene (PE) is evaluated from an atomistic point of view, with the combination of quantum chemical calculation and kinetic Monte Carlo simulations. Hole hopping rate between PE chains are computed by Fermi's golden rule and Marcus rate expression. It turns out that hole transfer in PE occurs in a hopping regime rather than in a band regime even for crystalline structure without any inherent structural disorders. The results indicate that in crystalline PE, hole
In order to evaluate the carrier transfer properties in polymers with flexible backbones, we have proposed a simplified multi-scale modeling approach combining molecular dynamics simulations, first-principles calculations and kinetic Monte Carlo simulations. Hole transfer in amorphous polyethylene (PE) is studied as a model system. It is shown that the characteristic length scale of hole localized states in PE is comparable to the Kuhn length of PE, which is the characteristic length scale in te
Recently, hole mobilities in polyethylene (PE) oligomers has been investigated by means of Marcus theory. Although it is well known that Marcus theory is successfully applied to various organic semiconductors, strictly speaking, charge transfer in organic molecules requires quantum mechanical treatment to account for quantum nuclear tunneling between vibrational levels. We evaluate hole transfer rates between PE oligomers by Fermi's golden rule (FGR) rate expression and by classical Marcus rate
Highly-selective, high-speed aromatic and aliphatic Claisen rearrangement was shown to give the corresponding product in an excellent yield induced by subcritical water microreaction in the absence of catalyst.
Despite its importance, carrier conduction in electrical insulators is poorly understood. This work presents a computational study of hole conduction in single crystalline alkanes (n-C18H38 and n-C36H74). Hole mobilities are computed with the combination of molecular dynamics simulation, quantum chemical calculation, and the kinetic Monte Carlo method. The hole hopping rate is computed by the Fermi golden rule rate kernel without high temperature approximation. A strong correlation between the a
In recent years, excess electron transfer in organic liquids has attracted increasing interest owing to the emerging class of liquid organic semiconductors. In this study, to achieve a comprehensive understanding of electron conduction in liquids, we investigate hopping electron conduction in liquids from an atomistic viewpoint. High-pressure liquid benzene is chosen as a simple model system. Hopping electron mobility is computed using a combination of molecular dynamics simulations, quantum che
Fast and furious: A wide range of alcohols are acylated by acetic anhydride, in the absence of catalyst, in subcritical water in a flow-type microreaction system. The esters are selectively produced in high yields at temperatures of 200 to 250 °C. Varying the amount of acetic anhydride added with respect to the alcohols allows the regioselective acylation of one or both hydroxy groups of various dihydroxy compounds (see picture). Supporting information for this article is available on the WWW un
First principles calculations are utilized in order to gain a better understanding of charge injection from metals to insulators. As a starting point, a comparative study of hole injection into polyethylene (PE) oligomer and ethylene-vinyl acetate (EVA) oligomer is conducted. We evaluate the hole injection barriers at metal/PE oligomer and metal/EVA oligomer interfaces in two ways: (1) from band-plus-lineup based approach and (2) from density of states based analysis. In line with experimental f
The present study derives a formulation of the finite-difference time-domain (FDTD) method appropriate for analyzing the transient behavior of elastic wave fields in the Y - Z plane of Quartz. It is shown that this formulation may easily be adapted for use on arbitrary anisotropic solids. The staggered lattice network of the present study differs from that of an isotropic solid only in the requirement of two variables on a particle velocity node and three variables on a stress node, in contrast
Silicone gel is used to encapsulate power electronic circuits. The weakness of this insulation system is surface discharges which degrade silicone gel. In this paper, various features of surface discharge in gel are evaluated by analyzing the motion of cavities induced by discharges and by measuring dynamic potential distributions of surface discharges in gel. The results indicated that charges accumulated at the cavity surface contribute to retaining the cavity path. Temporal response of the po
A new diagonally staggered grid configuration is proposed for the finite-difference time-domain analysis of elastic wave fields. The structure of the grid is the same as a standard staggered grid, but the diagonals of the standard grid lie parallel to the coordinate axes of the field of analysis in this new configuration. Adopting this grid configuration allows a natural implementation of antisymmetric stress boundary conditions, as is required when implementing free boundaries for example. In i
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