Naomichi Hatano - Profile on Academia.edu (original) (raw)
Papers by Naomichi Hatano
Double degeneracy in the ground state of the 3D ±J spin glass
Computer Physics Communications, Aug 1, 2002
ABSTRACT
Six-Vertex Model with an Frustrated Impurity
Journal of the Physical Society of Japan, Oct 15, 1997
ABSTRACT
Journal of Electronic Materials, Dec 23, 2011
The dependence of the current-induced cooling effect on the electron mobility l e is explored for... more The dependence of the current-induced cooling effect on the electron mobility l e is explored for a two-dimensional electron gas (2DEG) subjected to a perpendicular magnetic field. We calculate the distributions of the electrochemical potentials and the temperatures under a magnetic field, fully taking account of thermoelectric and thermomagnetic phenomena. Whereas the electrochemical potential and the electric current remain qualitatively unchanged, the temperature distribution exhibits drastic mobility dependence. The lower-mobility system has cold and hot areas at opposite corners, which results from the heat current brought about by the Ettingshausen effect in the vicinity of the adiabatic boundaries. The cooling effect is intensified by an increase in l e . Intriguingly, the cold and hot areas change places with each other as the mobility l e is further increased. This is because the heating current on the adiabatic edges due to the Righi-Leduc effect exceeds that due to the Ettingshausen effect in the opposite direction.
Bulletin of the American Physical Society, Mar 15, 2006
Nonadiabatic Transition in the Quantum Hall Effect MANABU MACHIDA, NAOMICHI HATANO, IIS, Universi... more Nonadiabatic Transition in the Quantum Hall Effect MANABU MACHIDA, NAOMICHI HATANO, IIS, University of Tokyo, JUN GORYO, Aoyama Gakuin University -We analyze the nonadiabatic transition in a 2D electron system with a periodic potential in the quantum Hall regime. We obtain corrections to the Chern-number term of the Hall conductance and a non-vanishing diagonal conductance. We treat the electric field as a time-dependent vector potential in the Hamiltonian. We calculate the time evolution of the density operator taking account of the first order of the electric field, and thereby study the electric conduction when the system evolves nonadiabatically. We thus obtain analytical expressions of the diagonal and off-diagonal conductances and calculate them numerically.
Bulletin of the American Physical Society, Mar 6, 2007
The American Physical Society Time-Dependent Conductivity in the Quantum Hall Effect MAN-ABU MACH... more The American Physical Society Time-Dependent Conductivity in the Quantum Hall Effect MAN-ABU MACHIDA, NAOMICHI HATANO, The University of Tokyo, Japan, JUN GORYO, Aoyama Gakuin University -We analyze the quantum Hall effect in a 2D electron system with a periodic potential. We show that the conductivity begins to oscillate in time when an electric field is suddenly switched on. Assuming linear response, we obtain an analytical expression of the time-dependent conductivity. The time dependence comes theoretically from the Fourier components of the response function with nonzero frequencies. The amplitude of the oscillation gradually decreases as a function of time and the conductivity eventually approaches to its average, which is given by the Chern number according to the Kubo formula. We numerically calculate the temporal oscillation of the conductivity in the case of a superlattice in a semiconductor. We find that both the Hall and diagonal conductivities oscillate with a period of pico to nano seconds.
Numerical-Diagonalization Analyses of an Effective Hamiltonian for the Haldane System
Journal of the Physical Society of Japan, Sep 15, 1994
ABSTRACT
Journal of Electronic Materials, Jan 4, 2011
We consider thermoelectric effects in a pseudo-one-dimensional electron gas (P1DEG) with a spin-o... more We consider thermoelectric effects in a pseudo-one-dimensional electron gas (P1DEG) with a spin-orbit interaction (SOI). The SOI splits the dispersion relation of the P1DEG into subbands with an energy gap. We find quantum oscillations in transport coefficients, which coincide with the locations of the subband edges, as a function of the electrochemical potential.
Temperature Distribution in Two-Dimensional Electron Gases under a Strong Magnetic Field
Journal of Electronic Materials, Nov 25, 2010
ABSTRACT Two-dimensional electron gases having an electrochemical potential gradient under a magn... more ABSTRACT Two-dimensional electron gases having an electrochemical potential gradient under a magnetic field are numerically examined using the finite-difference method. The temperature, voltage, electric current, and heat flux are calculated from transport equations describing thermoelectric and thermomagnetic effects, namely the Hall, Nernst, Ettingshausen, and Righi–Leduc effects. The results show that a magnetic field distorts equipotential lines and generates an uneven temperature distribution. In particular, a part of the system is found to become colder than the temperature of the heat baths. The cooling effect under a strong magnetic field is due primarily to the Ettingshausen and Hall effects.
Temperature distribution in nano-devices under a strong magnetic field
Computer Physics Communications, 2011
ABSTRACT The thermoelectric and thermomagnetic phenomena of two-dimensional electron gases at low... more ABSTRACT The thermoelectric and thermomagnetic phenomena of two-dimensional electron gases at low temperatures are numerically examined using the finite-difference method. The temperature and the voltage are calculated from transport equations describing thermoelectric and thermomagnetic effects. The results demonstrate that a magnetic field distorts equipotential lines and generates an uneven distribution of the temperature, which can cause inhomogeneous heating of experimental systems. In particular, a part of the system is found to be colder than the temperature of the heat baths.
CFT estimates of the universal Binder parameter for quantum ground-state transitions in one dimension
Journal of physics, Apr 21, 1994
ABSTRACT
Linear Algebra and its Applications, Apr 1, 2009
The concept of returnability is proposed for complex directed networks (digraphs). It can be seen... more The concept of returnability is proposed for complex directed networks (digraphs). It can be seen as a generalization of the concept of reciprocity. Two measures of the returnability are introduced. We establish closed formulas for the calculation of the returnability measures, which are also related to the digraph spectrum. The two measures are calculated for simple examples of digraphs as well as for real+world complex directed networks and are compared with the reciprocity.
Springer proceedings in physics, 2000
Atarnos National Laboratory, an affirmative actionlequal opportunity employer, is operated by the... more Atarnos National Laboratory, an affirmative actionlequal opportunity employer, is operated by the Uniwxsity of California for the U.S. Department of Energy under contract W-7405-ENG-36. By acceptance of this article, the publisher recognizes that the U.S. Gowmment retains a nonexclusive, royalty-free license to publish or reproduce the published form of HIS contrfbtilon, or to allow others to do .s0,for U.S. Government purposes. Los Alarnos National Laboratory requests that the pubiisher identify this article as work Wfforrned under the auspices of the U.S. Department of Energy. Los Alamos National Laboratory strongly sup~rts academic freedom and a researcher's right to putrhsh; as an institution, however, the Laboratory does not endorse the viewpoint of a pukiiition or guarantee its technical correctness. Form636(lo/96) DISCLAIMER
An explosive diffusion on a social network
arXiv (Cornell University), Nov 12, 2012
We explain a possible mechanism of an information spreading on a network which spreads extremely ... more We explain a possible mechanism of an information spreading on a network which spreads extremely far from a seed node, namely the viral spreading. On the basis of a model of the information spreading in an online social network, in which the dynamics is expressed as a random multiplicative process of the spreading rates, we will show that the correlation between the spreading rates enhances the chance of the viral spreading, shifting the tipping point at which the spreading goes viral.
Numerical CAM Analysis of Critical Phenomena in Spin Systems
Springer proceedings in physics, 1992
ABSTRACT
arXiv (Cornell University), Mar 18, 2003
Power-law distributions with various exponents are studied. We first introduce a simple and gener... more Power-law distributions with various exponents are studied. We first introduce a simple and generic model that reproduces Zipf's law. We can regard this model both as the time evolution of the population of cities and that of the asset distribution. We show that our model is very robust against various variations. Next, we explain theoretically why our model reproduces Zipf's law. By considering the time-evolution equation of our model, we see that the essence of Zipf's law is an asymmetric random walk in a logarithmic scale. Finally, we extend our model by introducing an additional asymmetry. We show that the extended model reproduces various power-law exponents. By extending the theoretical argument for Zipf's law, we find a simple equation of the power-law exponent.
arXiv (Cornell University), Nov 16, 2022
Quantum thermodynamics explores novel thermodynamic phenomena that emerge when interactions betwe... more Quantum thermodynamics explores novel thermodynamic phenomena that emerge when interactions between macroscopic systems and microscopic quantum ones go into action. Among various issues, quantum heat engines, in particular, have attracted much attention as a critical step in theoretical formulation of quantum thermodynamics and investigation of efficient use of heat by means of quantum resources. In the present paper, we focus on heat absorption and emission processes as well as work extraction processes of a quantum Otto cycle. We describe the former as non-Markovian dynamics, and thereby find that the interaction energy between a macroscopic heat bath and a microscopic qubit is not negligible. Specifically, we reveal that the interaction energy is divided into the system and the bath in a region of the short interaction time and remains negative in the region of the long interaction time. In addition, a counterintuitive energy flow from the system and the interaction energy to the hot bath occurs in another region of the short interaction time. We quantify these effects by defining an index of non-Markovianity in terms of the interaction energy. With this behavior of the interaction energy, we show that a non-Markovian quantum Otto cycle can switch functions such as an engine as well as a heater or a heat pump by controlling the interaction time with the heat bath. In particular, the qubit itself loses its energy if we shorten the interaction time, and in this sense, the qubit is cooled through the cycle. This property has a possibility of being utilized for cooling the qubits in quantum computing. We also describe the work extraction from the microscopic system to a macroscopic system like us humans as an indirect measurement process by introducing a work storage as a new reservoir.
Research Report NIFS Series: NIFS-953
Research Report NIFS Series: NIFS-954
Annual Report of National Institute for Fusion Science, Jan 27, 2011
Cam in Quantum Spin Systems
Double degeneracy in the ground state of the 3D ±J spin glass
Computer Physics Communications, Aug 1, 2002
ABSTRACT
Six-Vertex Model with an Frustrated Impurity
Journal of the Physical Society of Japan, Oct 15, 1997
ABSTRACT
Journal of Electronic Materials, Dec 23, 2011
The dependence of the current-induced cooling effect on the electron mobility l e is explored for... more The dependence of the current-induced cooling effect on the electron mobility l e is explored for a two-dimensional electron gas (2DEG) subjected to a perpendicular magnetic field. We calculate the distributions of the electrochemical potentials and the temperatures under a magnetic field, fully taking account of thermoelectric and thermomagnetic phenomena. Whereas the electrochemical potential and the electric current remain qualitatively unchanged, the temperature distribution exhibits drastic mobility dependence. The lower-mobility system has cold and hot areas at opposite corners, which results from the heat current brought about by the Ettingshausen effect in the vicinity of the adiabatic boundaries. The cooling effect is intensified by an increase in l e . Intriguingly, the cold and hot areas change places with each other as the mobility l e is further increased. This is because the heating current on the adiabatic edges due to the Righi-Leduc effect exceeds that due to the Ettingshausen effect in the opposite direction.
Bulletin of the American Physical Society, Mar 15, 2006
Nonadiabatic Transition in the Quantum Hall Effect MANABU MACHIDA, NAOMICHI HATANO, IIS, Universi... more Nonadiabatic Transition in the Quantum Hall Effect MANABU MACHIDA, NAOMICHI HATANO, IIS, University of Tokyo, JUN GORYO, Aoyama Gakuin University -We analyze the nonadiabatic transition in a 2D electron system with a periodic potential in the quantum Hall regime. We obtain corrections to the Chern-number term of the Hall conductance and a non-vanishing diagonal conductance. We treat the electric field as a time-dependent vector potential in the Hamiltonian. We calculate the time evolution of the density operator taking account of the first order of the electric field, and thereby study the electric conduction when the system evolves nonadiabatically. We thus obtain analytical expressions of the diagonal and off-diagonal conductances and calculate them numerically.
Bulletin of the American Physical Society, Mar 6, 2007
The American Physical Society Time-Dependent Conductivity in the Quantum Hall Effect MAN-ABU MACH... more The American Physical Society Time-Dependent Conductivity in the Quantum Hall Effect MAN-ABU MACHIDA, NAOMICHI HATANO, The University of Tokyo, Japan, JUN GORYO, Aoyama Gakuin University -We analyze the quantum Hall effect in a 2D electron system with a periodic potential. We show that the conductivity begins to oscillate in time when an electric field is suddenly switched on. Assuming linear response, we obtain an analytical expression of the time-dependent conductivity. The time dependence comes theoretically from the Fourier components of the response function with nonzero frequencies. The amplitude of the oscillation gradually decreases as a function of time and the conductivity eventually approaches to its average, which is given by the Chern number according to the Kubo formula. We numerically calculate the temporal oscillation of the conductivity in the case of a superlattice in a semiconductor. We find that both the Hall and diagonal conductivities oscillate with a period of pico to nano seconds.
Numerical-Diagonalization Analyses of an Effective Hamiltonian for the Haldane System
Journal of the Physical Society of Japan, Sep 15, 1994
ABSTRACT
Journal of Electronic Materials, Jan 4, 2011
We consider thermoelectric effects in a pseudo-one-dimensional electron gas (P1DEG) with a spin-o... more We consider thermoelectric effects in a pseudo-one-dimensional electron gas (P1DEG) with a spin-orbit interaction (SOI). The SOI splits the dispersion relation of the P1DEG into subbands with an energy gap. We find quantum oscillations in transport coefficients, which coincide with the locations of the subband edges, as a function of the electrochemical potential.
Temperature Distribution in Two-Dimensional Electron Gases under a Strong Magnetic Field
Journal of Electronic Materials, Nov 25, 2010
ABSTRACT Two-dimensional electron gases having an electrochemical potential gradient under a magn... more ABSTRACT Two-dimensional electron gases having an electrochemical potential gradient under a magnetic field are numerically examined using the finite-difference method. The temperature, voltage, electric current, and heat flux are calculated from transport equations describing thermoelectric and thermomagnetic effects, namely the Hall, Nernst, Ettingshausen, and Righi–Leduc effects. The results show that a magnetic field distorts equipotential lines and generates an uneven temperature distribution. In particular, a part of the system is found to become colder than the temperature of the heat baths. The cooling effect under a strong magnetic field is due primarily to the Ettingshausen and Hall effects.
Temperature distribution in nano-devices under a strong magnetic field
Computer Physics Communications, 2011
ABSTRACT The thermoelectric and thermomagnetic phenomena of two-dimensional electron gases at low... more ABSTRACT The thermoelectric and thermomagnetic phenomena of two-dimensional electron gases at low temperatures are numerically examined using the finite-difference method. The temperature and the voltage are calculated from transport equations describing thermoelectric and thermomagnetic effects. The results demonstrate that a magnetic field distorts equipotential lines and generates an uneven distribution of the temperature, which can cause inhomogeneous heating of experimental systems. In particular, a part of the system is found to be colder than the temperature of the heat baths.
CFT estimates of the universal Binder parameter for quantum ground-state transitions in one dimension
Journal of physics, Apr 21, 1994
ABSTRACT
Linear Algebra and its Applications, Apr 1, 2009
The concept of returnability is proposed for complex directed networks (digraphs). It can be seen... more The concept of returnability is proposed for complex directed networks (digraphs). It can be seen as a generalization of the concept of reciprocity. Two measures of the returnability are introduced. We establish closed formulas for the calculation of the returnability measures, which are also related to the digraph spectrum. The two measures are calculated for simple examples of digraphs as well as for real+world complex directed networks and are compared with the reciprocity.
Springer proceedings in physics, 2000
Atarnos National Laboratory, an affirmative actionlequal opportunity employer, is operated by the... more Atarnos National Laboratory, an affirmative actionlequal opportunity employer, is operated by the Uniwxsity of California for the U.S. Department of Energy under contract W-7405-ENG-36. By acceptance of this article, the publisher recognizes that the U.S. Gowmment retains a nonexclusive, royalty-free license to publish or reproduce the published form of HIS contrfbtilon, or to allow others to do .s0,for U.S. Government purposes. Los Alarnos National Laboratory requests that the pubiisher identify this article as work Wfforrned under the auspices of the U.S. Department of Energy. Los Alamos National Laboratory strongly sup~rts academic freedom and a researcher's right to putrhsh; as an institution, however, the Laboratory does not endorse the viewpoint of a pukiiition or guarantee its technical correctness. Form636(lo/96) DISCLAIMER
An explosive diffusion on a social network
arXiv (Cornell University), Nov 12, 2012
We explain a possible mechanism of an information spreading on a network which spreads extremely ... more We explain a possible mechanism of an information spreading on a network which spreads extremely far from a seed node, namely the viral spreading. On the basis of a model of the information spreading in an online social network, in which the dynamics is expressed as a random multiplicative process of the spreading rates, we will show that the correlation between the spreading rates enhances the chance of the viral spreading, shifting the tipping point at which the spreading goes viral.
Numerical CAM Analysis of Critical Phenomena in Spin Systems
Springer proceedings in physics, 1992
ABSTRACT
arXiv (Cornell University), Mar 18, 2003
Power-law distributions with various exponents are studied. We first introduce a simple and gener... more Power-law distributions with various exponents are studied. We first introduce a simple and generic model that reproduces Zipf's law. We can regard this model both as the time evolution of the population of cities and that of the asset distribution. We show that our model is very robust against various variations. Next, we explain theoretically why our model reproduces Zipf's law. By considering the time-evolution equation of our model, we see that the essence of Zipf's law is an asymmetric random walk in a logarithmic scale. Finally, we extend our model by introducing an additional asymmetry. We show that the extended model reproduces various power-law exponents. By extending the theoretical argument for Zipf's law, we find a simple equation of the power-law exponent.
arXiv (Cornell University), Nov 16, 2022
Quantum thermodynamics explores novel thermodynamic phenomena that emerge when interactions betwe... more Quantum thermodynamics explores novel thermodynamic phenomena that emerge when interactions between macroscopic systems and microscopic quantum ones go into action. Among various issues, quantum heat engines, in particular, have attracted much attention as a critical step in theoretical formulation of quantum thermodynamics and investigation of efficient use of heat by means of quantum resources. In the present paper, we focus on heat absorption and emission processes as well as work extraction processes of a quantum Otto cycle. We describe the former as non-Markovian dynamics, and thereby find that the interaction energy between a macroscopic heat bath and a microscopic qubit is not negligible. Specifically, we reveal that the interaction energy is divided into the system and the bath in a region of the short interaction time and remains negative in the region of the long interaction time. In addition, a counterintuitive energy flow from the system and the interaction energy to the hot bath occurs in another region of the short interaction time. We quantify these effects by defining an index of non-Markovianity in terms of the interaction energy. With this behavior of the interaction energy, we show that a non-Markovian quantum Otto cycle can switch functions such as an engine as well as a heater or a heat pump by controlling the interaction time with the heat bath. In particular, the qubit itself loses its energy if we shorten the interaction time, and in this sense, the qubit is cooled through the cycle. This property has a possibility of being utilized for cooling the qubits in quantum computing. We also describe the work extraction from the microscopic system to a macroscopic system like us humans as an indirect measurement process by introducing a work storage as a new reservoir.
Research Report NIFS Series: NIFS-953
Research Report NIFS Series: NIFS-954
Annual Report of National Institute for Fusion Science, Jan 27, 2011
Cam in Quantum Spin Systems