KINETIC ENERGY AND PHASE SEPARATION IN A DOPED ANTIFERROMAGNET

1995 ◽  
Vol 09 (24) ◽  
pp. 1623-1629 ◽  
Author(s):  
XIN XU ◽  
YUN SONG ◽  
SHIPING FENG
Keyword(s):  
Phase Separation ◽  
Kinetic Energy ◽  
Ground State ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Numerical Result ◽  
The Mean ◽  
State Kinetic

The ground-state kinetic energy of the t-J model is studied within the mean field approximation by using the fermion-spin transformation, the results show that the mean field ground-state kinetic energy is close to the numerical result at under dopings, and roughly consistent with the numerical result at optimal dopings. It is also shown that the frustration term J′ is favourable to diminish the range of the phase seperation in the t-J model.

scholarly journals Mean-field Solution of the mixed spin-1 and spin-5/2Ising system with different single-ion anisotropies

2009 ◽  
Vol 6 (4) ◽  
pp. 784-789
Author(s):  
Baghdad Science Journal
Keyword(s):  
Phase Diagram ◽  
Ground State ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Two Dimensional ◽  
Ground State Phase Diagram ◽  
Mixed Spin ◽  
Bogoliubov Inequality ◽  
The Mean

The mixed-spin ferrimagnetic Ising system consists of two-dimensional sublattices A and B with spin values and respectively .By used the mean-field approximation MFA of Ising model to find magnetism( ).In order to determined the best stabile magnetism , Gibbs free energy employ a variational method based on the Bogoliubov inequality .The ground-state (Phase diagram) structure of our system can easily be determined at , we find six phases with different spins values depend on the effect of a single-ion anisotropies .these lead to determined the second , first orders transition ,and the tricritical points as well as the compensation phenomenon .

scholarly journals Unconventional phase separation in the model 2D spin-pseudospin system

2018 ◽  
Vol 185 ◽  
pp. 11006 ◽  
Author(s):  
K.S. Budrin ◽  
Yu.D. Panov ◽  
A.S. Moskvin ◽  
A.A. Chikov
Keyword(s):  
Monte Carlo ◽  
Phase Separation ◽  
Ground State ◽  
Spin Exchange ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Spin Subsystem ◽  
Monte Carlo Calculations ◽  
Antiferromagnetic Ordering

The competition of charge and spin orderings is a challenging problem for strongly correlated systems, in particular, for high-Tc cuprates. We addressed a simplified static 2D spin-pseudospin model which takes into account both conventional spin exchange coupling and the on-site and inter-site charge correlations. Classical Monte-Carlo calculations for large square lattices show that homogeneous ground state antiferromagnetic solutions found in a mean-field approximation are unstable with respect to phase separation into the charge and spin subsystems behaving like immiscible quantum liquids. In this case, with lowering of a temperature one can observe two sequential phase transitions: first, antiferromagnetic ordering in the spin subsystem diluted by randomly distributed charges, then, the charge condensation in the charge droplets. The inhomogeneous droplet phase reduces the energy of the system and changes the diagram of the ground states. On the other hand, the ground state energy of charge-ordered state in a mean-field approximation exactly matches the numerical Monte-Carlo calculations. The doped charges in this case are distributed randomly over a system in the whole temperature range. Various thermodynamic properties of the 2D spin-pseudospin system are studied by Monte-Carlo simulation.

New statistical lattice model with double honeycomb symmetry

2014 ◽  
Vol 28 (15) ◽  
pp. 1450086 ◽  
Author(s):  
S. Naji ◽  
A. Belhaj ◽  
H. Labrim ◽  
M. Bhihi ◽  
A. Benyoussef ◽  
...  
Keyword(s):  
Ground State ◽  
Lattice Model ◽  
Present Model ◽  
Hexagonal Lattice ◽  
Mean Field ◽  
Field Approximation ◽  
Hexagonal Structure ◽  
Mean Field Approximation ◽  
Two Dimensional Materials ◽  
The Mean

Inspired from the connection between Lie symmetries and two-dimensional materials, we propose a new statistical lattice model based on a double hexagonal structure appearing in the G2 symmetry. We first construct an Ising-1/2 model, with spin values σ = ±1, exhibiting such a symmetry. The corresponding ground state shows the ferromagnetic, the antiferromagnetic, the partial ferrimagnetic and the topological ferrimagnetic phases depending on the exchange couplings. Then, we examine the phase diagrams and the magnetization using the mean field approximation (MFA). Among others, it has been suggested that the present model could be localized between systems involving the triangular and the single hexagonal lattice geometries.

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