Browsing by Author "Minh-Tien, T"

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Charge ordered ferromagnetic phase in manganites
(2003-04-11)
Minh-Tien, T
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電子物理學系
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Department of Electrophysics
A mechanism for charge ordered ferromagnetic phase in manganites is proposed. The mechanism is based on the double exchange in the presence of diagonal disorder. It is modeled by a combination of the Ising double-exchange and the Falicov-Kimball model. Within the dynamical mean-field theory the charge and spin correlation function are explicitly calculated. It is shown that the system exhibits two successive phase transitions. The first one is the ferromagnetic phase transition, and the second one is a charge ordering. As a result a charge ordered ferromagnetic phase is stabilized at low temperature.
Emergence of quasimetallic state in a disordered two-dimensional electron gas due to strong interactions
(2003-12-01)
Rosenstein, B
;
Minh-Tien, T
;
交大名義發表
;
電子物理學系
;
National Chiao Tung University
The interrelation between disorder and interactions in two-dimensional electron liquid is studied beyond weak-coupling perturbation theory. Strong repulsion significantly reduces the electronic density of states on the Fermi level. This makes the electron liquid more rigid and strongly suppresses elastic scattering off impurities. As a result the weak localization, although ultimately present at zero temperature and infinite sample size, is unobservable at experimentally accessible temperature at high enough densities. Therefore practically there exists a well-defined metallic state. We study diffusion of electrons in this state and find that the diffusion pole is significantly modified due to "mixture" with static photons similar to the Anderson-Higgs mechanism in superconductivity. As a result several effects stemming from the long-range nature of diffusion such as the Aronov-Altshuler logarithmic corrections to conductivity are less pronounced.