Daijiro Yoshioka
University of Tokyo
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Featured researches published by Daijiro Yoshioka.
Physical Review B | 1995
K. Moon; Hiroyuki Mori; Kun Yang; S. M. Girvin; A. H. MacDonald; L. Zheng; Daijiro Yoshioka; Shou-Cheng Zhang
At strong magnetic fields double-layer two-dimensional-electron-gas systems can form an unusual broken symmetry state with spontaneous inter-layer phase coherence. In this paper we explore the rich variety of quantum and finite-temperature phase transitions associated with this broken symmetry. We describe the system using a pseudospin language in which the layer degree-of-freedom is mapped to a fictional spin 1/2 degree-of-freedom. With this mapping the spontaneous symmetry breaking is equivalent to that of a spin 1/2 easy-plane ferromagnet. In this language spin-textures can carry a charge. In particular, vortices carry e/2 electrical charge and vortex-antivortex pairs can be neutral or carry charge e. We derive an effective low-energy action and use it to discuss the charged and collective neutral excitations of the system. We have obtained the parameters of the Landau-Ginzburg functional from first-principles estimates and from finite-size exact diagonalization studies. We use these results to estimate the dependence of the critical temperature for the Kosterlitz-Thouless phase transition on layer separation.
Journal of the Physical Society of Japan | 1990
Daijiro Yoshioka; A. H. MacDonald
Two-dimensional electron-hole systems with long excitonic life-times can be realized in double quantum well systems by applying an electric field which localizes electrons and holes in opposite wells. The ground state of such a system is investigated theoretically and numerically in the strong magnetic field limit. It is shown that when the separation between the electron layer and the hole layer, d , is small, an excitonic condensate state is realized. On the other hand, when d is large, either independent fractional quantum Hall states for electrons and holes or coupled Wigner crystal (dipole density wave) states may be realized depending on the filling factor. The difference in photoluminescence spectra between these states is discussed.
Physical Review Letters | 1994
Kun Yang; K. Moon; Lian Zheng; A. H. MacDonald; S. M. Girvin; Daijiro Yoshioka; Shou-Cheng Zhang
Double layer quantum Hall systems have interesting properties associated with interlayer correlations. At
Journal of the Physical Society of Japan | 1989
Daijiro Yoshioka
\nu =1/m
Journal of the Physical Society of Japan | 1981
Daijiro Yoshioka; Hidetoshi Fukuyama
where
Physical Review B | 1994
H. Kato; Daijiro Yoshioka
m
Journal of the Physical Society of Japan | 1986
Daijiro Yoshioka
is an odd integer they exhibit spontaneous symmetry breaking equivalent to that of spin
Physical Review Letters | 2001
Naokazu Shibata; Daijiro Yoshioka
1/2
Journal of the Physical Society of Japan | 1979
Daijiro Yoshioka; Hidetoshi Fukuyama
easy-plane ferromagnets, with the layer degree of freedom playing the role of spin. We explore the rich variety of quantum and finite temperature phase transitions in these systems. In particular, we show that a magnetic field oriented parallel to the layers induces a highly collective commensurate-incommensurate phase transition in the magnetic order.
Journal of the Physical Society of Japan | 1989
Daijiro Yoshioka
A nearly half-filled two-dimensional Hubbard model has been considered as a model for a high transition temperature oxide superconductor. A new scheme to treat this model, the slave-fermion method, is proposed. The method is applied to the model in the limit of large U at half-filled, where the model reduces to the antiferromagnetic Heisenberg model. It is shown that the ground state energy becomes much lower in the slave-fermion scheme than that in the slave-boson scheme. The ground state shows antiferromagnetic long range order at T =0.