JaLCDOI 10.18926/15395
FullText URL Mem_Fac_Eng_OU_27_1_65.pdf
Author Nara, Shigetoshi| Hara Yuji| Totsuji, Hiroo|
Abstract Quantum mechnical electron wave transfer between two quantum wires which are weakly coupled via a thin potential barrier is considered. The total electronic states are calculated with both analytical ( no field case ) and numerical methods ( under applied electric fields ). The transfer efficiency is evaluated for several specified cases of geometrical structures, potential barrier heights and the externally applied electric field. Estimated trasfer time is of the order of one picosecond in typical mesoscopic structures. The model in this paper can be used to determine important structure parameters for experiments on electron directional coupler controled by external elctric field.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 1992-11-25
Volume volume27
Issue issue1
Start Page 65
End Page 79
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002307405
JaLCDOI 10.18926/15403
FullText URL Mem_Fac_Eng_OU_27_2_19.pdf
Author Nara, Shigetoshi| Totsuji, Hiroo|
Abstract Numerical simulations of a single layer recurrent neural network model in which the synaptic connection matrix is formed by summing cyclic products of succesive patterns show that complex dynamics can occur with the reduction of a connectivity parameter which is the number of connection between neurons. The structure in these dynamics is discussed from the viewpoint of realizing complex function using complex dynamics.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 1993-03-25
Volume volume27
Issue issue2
Start Page 19
End Page 40
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002307451
JaLCDOI 10.18926/15418
FullText URL Mem_Fac_Eng_OU_26_1_51.pdf
Author Totsuji, Hiroo| Shirokoshi Hideki| Nara, Shigetoshi|
Abstract Variable shape molecular dynamics is formulated for the one-component plasma and the structural transition from the fcc lattice to the bcc lattice has been observed. It is emphasized that the condition of constant volume should be imposed when deformations of periodic boundary conditions are taken into account.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 1991-11-30
Volume volume26
Issue issue1
Start Page 51
End Page 59
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002307555
JaLCDOI 10.18926/15432
FullText URL Mem_Fac_Eng_OU_28_1_1.pdf
Author Nara, Shigetoshi| Miho Shigeru| Totsuji, Hiroo|
Abstract The structural stabilities of bulk Si, Ge, and GaAs are discussed based on the total energy evaluated by the summation of the band structure energy and the short-range repulsive potential between ions. The band structure energy is calculated by means of the simple tight-binding method. The tight-binding parameters are determined so as to fit to the results of a pseude potential calculation and Harrison's model is employed to include the influence of lattice deformation. The short-range-force is assumed to be of the exponential form and parameters are determined so as to reproduce an experimental value of bulk modulus. This treatment qualitatively well describes structural properties in spite of the simple computational procedure and roughly gives the known variation of the total energy for a <100> uniaxial strain. This method is able to be applied to an investigation of the structural stabilities of superlattices, for example, a strained layer superlattice consisting of hetero-semiconductors.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 1993-11-30
Volume volume28
Issue issue1
Start Page 1
End Page 25
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002307238
JaLCDOI 10.18926/15434
FullText URL Mem_Fac_Eng_OU_28_1_27.pdf
Author Totsuji, Hiroo| Tachibana Hiroyuki| Fujimura Hidenori| Nara, Shigetoshi|
Abstract The ground states of interacting electrons in coupled quantum wires are analyzed on the basis of the density functional theory. The exchange-correlation potential is calculated from 'exact' results given by the Green's function Monte Carlo method in two and three dimensions. It is shown that the critical density signifying the change from symmetrical to asymmetrical ground state is weakly dependent on the details of the exchange-correlation potential. These critical values are compared with the result of the three-dimensional analysis for a single wire.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 1993-11-30
Volume volume28
Issue issue1
Start Page 27
End Page 38
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002307565
JaLCDOI 10.18926/15444
FullText URL Mem_Fac_Eng_OU_26_2_129.pdf
Author Totsuji, Hiroo|
Abstract The spectrum of Schottky noise in ion storage rings is analyzed as density fluctuations in effectively one-dimensional plasmas. Strong coupling effects in these plasmas are discussed in relation to experimental observations.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 1992-03-28
Volume volume26
Issue issue2
Start Page 129
End Page 138
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002307668
JaLCDOI 10.18926/15449
FullText URL Mem_Fac_Eng_OU_22_15.pdf
Author Furutani, Yoichiro| Totsuji, Hiroo| Komaki Kunitaka| Tanabe Masahiro|
Abstract An effective potential of an isolated partially ionized high-Z ion, calculated within the framework of the statistical models of atoms, is injected into the one-electron Schrödinger equation, in view of evaluating the electron density and comparing it with the results of statistical models. Starting from this initial value, a self-consistent electron density is obtained on the basis of the density functional theory, where quantum natures of electrons are fully taken into account.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 1988-03-31
Volume volume22
Start Page 15
End Page 34
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002307361
JaLCDOI 10.18926/15450
FullText URL Mem_Fac_Eng_OU_22_35.pdf
Author Totsuji, Hiroo|
Abstract Several methods to derive thermodynamic sum rules for a system including charged particle are proposed and applied to charged mixtures as well as one-component systems. The validity of the statements is examined carefully with respect to the ordering in the powers of the wave number. As for the mixture of electrons and ions, it is shown how the aspect of the one-component plasma or the ionic mixture appears when electrons become strongly degenerate.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 1988-03-31
Volume volume22
Start Page 35
End Page 44
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002307661
JaLCDOI 10.18926/15468
FullText URL Mem_Fac_Eng_OU_23_1_69.pdf
Author Totsuji, Hiroo| Takei Makoto|
Abstract The statistical properties of two-dimensional systems of charges in semiconductor superlattices are analyzed and the dispersion relation of the plasma oscillation is calculated. The possibility to excite these oscillations by applying the electric field parallel to the structure is discussed.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 1988-11-22
Volume volume23
Issue issue1
Start Page 69
End Page 82
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002307988
JaLCDOI 10.18926/15482
FullText URL Mem_Fac_Eng_OU_24_1_93.pdf
Author Totsuji, Hiroo| Hatatani, Teruki|
Abstract Propagation of charged carriers in semiconductor superlattices is analyzed on the basis of the effective mass approximation with appropriate boundary conditions at heterojunctions taken into account. Applying the finite element method, clarified are the effects of details of the potential profile, such as linear and smooth gradings and random fluctuations, on characteristics of superlattices which are expected to work as collector barriers and energy filters in electronic devices.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 1989-11-29
Volume volume24
Issue issue1
Start Page 93
End Page 105
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002307513
JaLCDOI 10.18926/15490
FullText URL Mem_Fac_Eng_OU_25_1_51.pdf
Author Totsuji, Hiroo|
Abstract The superconductivity proximity effect in the dirty limit is revisited and equations and boundary conditions are obtained for the case of inhomogeneous media with continuously varying characteristic parameters.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 1990-12-14
Volume volume25
Issue issue1
Start Page 51
End Page 57
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002307188
JaLCDOI 10.18926/15497
FullText URL Mem_Fac_Eng_OU_24_2_41.pdf
Author Totsuji, Hiroo|
Abstract A possibility to control the microscopic superconducting channel based on the proximity effect is theoretically shown by a simple one-dimensional analysis of de Gennes' equation for the order parameter.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 1990-03-29
Volume volume24
Issue issue2
Start Page 41
End Page 47
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002307289
JaLCDOI 10.18926/14058
FullText URL Mem_Fac_Eng_OU_42_44.pdf
Author Ogawa Takafumi| Tsuruta, Kenji| Totsuji, Chieko| Totsuji, Hiroo| Hiroshi Iyetomi|
Abstract To analyze vibrational properties of Si crystal with a single charge-neutral vacancy, we perform large-scale simulations based on tight-binding molecular-dynamics method. Vibrational modes and frequencies are obtained by diagonalizing dynamical matrix within a harmonic approximation. Results indicate that there exist vibrational modes spatially localized around the vacancy and large frequency shifts associated with the localized modes contribute significantly to reduction of the vibrational free energy.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 2008-01
Volume volume42
Issue issue1
Start Page 44
End Page 47
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002308412
JaLCDOI 10.18926/14059
FullText URL Mem_Fac_Eng_OU_42_48.pdf
Author Totsuji, Chieko| Miyake Takashi| Nakanishi Kenta| Tsuruta, Kenji| Totsuji, Hiroo|
Abstract Based on the mapping introduced by the classical-map hypernetted-chain (CHNC) method, classical numerical simulations, Monte Carlo and molecular dynamics, have been applied to the twodimensional electron fluid and the results are compared with those of quantum Monte Carlo simulations hitherto reported. It is shown that polarization properties of the ground state obtained by the diffusion Monte Carlo method are reproduced within the accuracy of quantum simulations by both of two mapping functions for the quantum temperature which have been proposed within the CHNC method. These results may serve as the basis of numerical simulations based on the CHNC method which are applicable to finite non-periodic systems like quantum dots and systems at finite temperatures.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 2008-01
Volume volume42
Issue issue1
Start Page 48
End Page 52
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002308425
JaLCDOI 10.18926/14060
FullText URL Mem_Fac_Eng_OU_42_53.pdf
Author Chai Hong| Totsuji, Hiroo|
Abstract In order to transfer quantum information, the use of spin chains has been proposed and their transfer characteristics have been analyzed. As one of the latter, the maximum of the transfer probability over sufficiently long time period is often considered important and some examples with high maximum values have been given. In these examples, the coupling between neighboring spins are tuned so as to attain high efficiency. In this article, we discuss the effect of noise on the values of coupling constant. As a result, we propose a system where the efficiency is high and also the effect of noise is small.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 2008-01
Volume volume42
Issue issue1
Start Page 53
End Page 55
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002308635
JaLCDOI 10.18926/14061
FullText URL Mem_Fac_Eng_OU_42_56.pdf
Author Miyake Takashi| Totsuji, Chieko| Nakanishi Kenta| Tsuruta, Kenji| Totsuji, Hiroo|
Abstract We analyze the ground state of the two-dimensional quantum system of electrons confined in a parabolic potential with the system size around 100. We map the system onto a classical system on the basis of the classical-map hypernetted-chain (CHNC) method which has been proven to work in the integral-equation-based analyses of uniform unbounded systems and then apply classical numerical simulations. We find that the confined system undergoes the transition to the spin polarized state with the decrease of the average density and the corresponding critical value is as low as rs ∼ 0.3 in terms of the usual rs parameter estimated for the average density. As the ground state for given value of the rs parameter, our data give the critical value for the transition around 20 which is consistent with the known possibility. The advantage of our method is a direct applicability to geometrically complex systems which are difficult to analyze by integral equations. The application to the structure like quantum dots reported here is the first example of such applications.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 2008-01
Volume volume42
Issue issue1
Start Page 56
End Page 59
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002308633
JaLCDOI 10.18926/14119
FullText URL Mem_Fac_Eng_OU_40_1_31.pdf
Author Ogawa, Takafumi| Totsuji, Chieko| Tsuruta, Kenji| Totsuji, Hiroo|
Abstract We analyze the melting of spherical Yukawa clusters by Monte Carlo simulations. Spherical clusters are expected to be found in dusty plasmas in an isotropic environment such as microgravity and serve as a model for classical clusters. We obtain the specific heat through fluctuations of the potential energy and identify its peak as the transition temperature. Melting temperatures are compared with those of bulk Yukawa systems and it is confirmed that the melting temperature increases and approaches the bulk value with the increase of the system size.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 2006-01
Volume volume40
Issue issue1
Start Page 31
End Page 35
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002308329
JaLCDOI 10.18926/14120
FullText URL Mem_Fac_Eng_OU_40_1_36.pdf
Author Uchida, Atsushi| Totsuji, Chieko| Tsuruta, Kenji| Totsuji, Hiroo|
Abstract We present a Stochastic-Difference-Equation (SDE) approach to long time-scale molecular dynamics (MD) simulations, which are required for nanosecond-scale phenomena. In this method, the MD trajectory in a fixed time period is obtained as a stationary solution of an action functional based on an error accumulation of the equation of motion along the path, thus reducing the problem to a boundary-value problem, instead of an initial-value problem in the ordinary MD method. We apply the method to formation processes of Cu thin film via nanocluster deposition onto a substrate. The applicability of the SDE algorithm to the problem and the effects of the choice of SDE parameters on the optimization processes of configuration pathway are examined.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 2006-01
Volume volume40
Issue issue1
Start Page 36
End Page 39
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002308517
JaLCDOI 10.18926/14121
FullText URL Mem_Fac_Eng_OU_40_1_40.pdf
Author Takashi, Miyake| Totsuji, Chieko| Tsuruta, Kenji| Totsuji, Hiroo|
Abstract The electron system of arbitrary degeneracy can be mapped onto a classical system where electrons of the same spin are assigned an additional interaction and the effect of degeneracy is taken into account through an imaginative temperature. We apply this method to electrons in quantum dots modeled as two-dimensional electron liquid confined in a finite domain by a harmonic potential. We analyze distribution functions by molecular dynamics instead of solving integral equations which are not so useful in the case without translational invariance.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 2006-01
Volume volume40
Issue issue1
Start Page 40
End Page 43
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002308268
JaLCDOI 10.18926/14150
FullText URL Mem_Fac_Eng_39_1_46.pdf
Author Kadono, Keisuke| Totsuji, Chieko| Tsuruta, Kenji| Totsuji, Hiroo|
Abstract We present a real-space, polynomial-expansion approach to electron dynamics in nanostructured semiconductors. The Chebyshev expansion method is employed for efficient calculation of timeevolution of single-electron wave function. Details of the formulation are described. The method is applied to the electron transport in nanostructured semiconductors such as Si nanowires. The mean-square displacement and diffusivity of electron in Si chains are obtained as functions of length of the chains. The results show clearly ballistic behavior of electron in the pure Si chain.
Publication Title Memoirs of the Faculty of Engineering, Okayama University
Published Date 2005-01
Volume volume39
Issue issue1
Start Page 46
End Page 51
ISSN 0475-0071
language 英語
File Version publisher
NAID 120002308231