ANISOTROPY INFLUENCE ON THE STRIPED ANTIFERROMAGNETISM OF A FRUSTRATED HEISENBERG MODEL: AN APPLICATION TO IRON PNICTIDE MATERIALS

Motivated by several experimental studies of magnetic compounds related to iron pnictides, we examine thermodynamic properties of anisotropic J1a - J1b - Jc - J2 Heisenberg antiferromagnetic model. Our calculations are based on the two-time temperature Green's functions within several well-known decoupling approximations. We obtain excitation spectrum, correlation functions and the analytic expression for the critical temperature and compare our results to the existing experimental data. Results presented here could be of a great importance in the further investigations of similar magnetic systems.

CORRELATIONS IN HOT ASYMMETRIC NUCLEAR MATTER

The single-particle spectral functions in asymmetric nuclear matter are computed using the ladder approximation within the theory of finite temperature Green's functions. The internal energy and the momentum distributions of protons and neutrons are studied as a function of the density and the asymmetry of the system. The proton states are more strongly depleted when the asymmetry increases, whereas the occupation of the neutron states is enhanced compared to the symmetric case. Preliminary results for the entropy and the free energy are also presented.

Quantum Description of a Degenerate P-N Junction Coupled to an Electrical Circuit

A theory of Coulomb blockade of tunneling in a degenerate p-n junction is presented. Perturbation theory and temperature Green's functions are used to obtain the current–voltage characteristics. The formulation extends the theory of Coulomb blockade in MIM junctions, to junctions in which the characteristics of the device, is partly determined by the many particle interaction in the electrodes. Exact analytical expressions for the I-V at zero temperature and approximate expressions at nonzero temperatures are obtained. Among the novel features observed are: an asymmetry in the current–voltage characteristics even for voltages on the scale of the Coulomb blockade threshold and threshold like behavior below (e/2C).