1,427 research outputs found
Magnetic-Field-Induced Mott Transition in a Quasi-Two-Dimensional Organic Conductor
We investigated the effect of magnetic field on the highly correlated metal
near the Mott transition in the quasi-two-dimensional layered organic
conductor, -(BEDT-TTF)Cu[N(CN)]Cl, by the resistance
measurements under control of temperature, pressure, and magnetic field. It was
demonstrated that the marginal metallic phase near the Mott transition is
susceptible to the field-induced localization transition of the first order, as
was predicted theoretically. The thermodynamic consideration of the present
results gives a conceptual pressure-field phase diagram of the Mott transition
at low temperatures.Comment: 4 pages, 4 figure
Dynamics of Multiferroic Domain Wall in Spin-Cycloidal Ferroelectric DyMnO
We report the dielectric dispersion of the giant magnetocapacitance (GMC) in
multiferroic DyMnO over a wide frequency range. The GMC is found to be
attributable not to the softened electromagnon but to the electric-field-driven
motion of multiferroic domain wall (DW). In contrast to conventional
ferroelectric DWs, the present multiferroic DW motion holds extremely high
relaxation rate of s even at low temperatures. This
mobile nature as well as the model simulation suggests that the multiferroic DW
is not atomically thin as in ferroelectrics but thick, reflecting its magnetic
origin.Comment: 4 pages, 4 figure
Thermodynamic Relations in Correlated Systems
Several useful thermodynamic relations are derived for metal-insulator
transitions, as generalizations of the Clausius-Clapeyron and Eherenfest
theorems. These relations hold in any spatial dimensions and at any
temperatures. First, they relate several thermodynamic quantities to the slope
of the metal-insulator phase boundary drawn in the plane of the chemical
potential and the Coulomb interaction in the phase diagram of the Hubbard
model. The relations impose constraints on the critical properties of the Mott
transition. These thermodynamic relations are indeed confirmed to be satisfied
in the cases of the one- and two-dimensional Hubbard models. One of these
relations yields that at the continuous Mott transition with a diverging charge
compressibility, the doublon susceptibility also diverges. The constraints on
the shapes of the phase boundary containing a first-order metal-insulator
transition at finite temperatures are clarified based on the thermodynamic
relations. For example, the first-order phase boundary is parallel to the
temperature axis asymptotically in the zero temperature limit. The
applicability of the thermodynamic relations are not restricted only to the
metal-insulator transition of the Hubbard model, but also hold in correlated
systems with any types of phases in general. We demonstrate such examples in an
extended Hubbard model with intersite Coulomb repulsion containing the charge
order phase.Comment: 10 pages, 9 figure
Magnetic-Field-Induced Antiferromagnetism in Two-Dimensional Hubbard Model: Analysis of CeRhIn
We propose the mechanism for the magnetic-field-induced antiferromagnetic
(AFM) state in a two-dimensional Hubbard model in the vicinity of the AFM
quantum critical point (QCP), using the fluctuation-exchange (FLEX)
approximation by taking the Zeeman energy due to the magnetic field into
account. In the vicinity of the QCP, we find that the AFM correlation
perpendicular to is enhanced, whereas that parallel to is reduced. This
fact means that the finite magnetic field increases , with the AFM order
perpendicular to . The increment in can be understood in terms of the
reduction of both quantum and thermal fluctuations due to the magnetic field,
which is caused by the self-energy effect within the FLEX approximation. The
present study naturally explains the increment in in CeRhIn_5 under the
magnetic field found recently.Comment: 5 page
- …