Orbital selective crossover and Mott transitions in an asymmetric Hubbard model of cold atoms in optical lattices

We study the asymmetric Hubbard model at half-filling as a generic model to describe the physics of two species of repulsively interacting fermionic cold atoms in optical lattices. We use Dynamical Mean Field Theory to obtain the paramagnetic phase diagram of the model as function of temperature, interaction strength and hopping asymmetry. A Mott transition with a region of two coexistent solutions is found for all nonzero values of the hopping asymmetry. At low temperatures the metallic phase is a heavy Fermi-liquid, qualitatively analogous to the Fermi liquid state of the symmetric Hubbard model. Above a coherence temperature, an orbital-selective crossover takes place, wherein one fermionic species effectively localizes, and the resulting bad metallic state resembles the non-Fermi liquid state of the Falicov-Kimball model. We compute observables relevant to cold atom systems such as the double occupation, the specific heat and entropy and characterize their behavior in the different phases

Weak coupling study of decoherence of a qubit in disordered magnetic environments

We study the decoherence of a qubit weakly coupled to frustrated spin baths. We focus on spin-baths described by the classical Ising spin glass and the quantum random transverse Ising model which are known to have complex thermodynamic phase diagrams as a function of an external magnetic field and temperature. Using a combination of numerical and analytical methods, we show that for baths initally in thermal equilibrium, the resulting decoherence is highly sensitive to the nature of the coupling to the environment and is qualitatively different in different parts of the phase diagram. We find an unexpected strong non-Markovian decay of the coherence when the random transverse Ising model bath is prepared in an initial state characterized by a finite temperature paramagnet. This is contrary to the usual case of exponential decay (Markovian) expected for spin baths in finite temperature paramagnetic phases, thereby illustrating the importance of the underlying non-trivial dynamics of interacting quantum spinbaths.Comment: 12 pages, 18 figure

Phase diagram of the asymmetric Hubbard model and an entropic chromatographic method for cooling cold fermions in optical lattices

We study the phase diagram of the asymmetric Hubbard model (AHM), which is characterized by different values of the hopping for the two spin projections of a fermion or equivalently, two different orbitals. This model is expected to provide a good description of a mass-imbalanced cold fermionic mixture in a 3D optical lattice. We use the dynamical mean field theory to study various physical properties of this system. In particular, we show how orbital-selective physics, observed in multi-orbital strongly correlated electron systems, can be realized in such a simple model. We find that the density distribution is a good probe of this orbital selective crossover from a Fermi liquid to a non-Fermi liquid state. Below an ordering temperature $T_o$, which is a function of both the interaction and hopping asymmetry, the system exhibits staggered long range orbital order. Apart from the special case of the symmetric limit, i.e., Hubbard model, where there is no hopping asymmetry, this orbital order is accompanied by a true charge density wave order for all values of the hopping asymmetry. We calculate the order parameters and various physical quantities including the thermodynamics in both the ordered and disordered phases. We find that the formation of the charge density wave is signaled by an abrupt increase in the sublattice double occupancies. Finally, we propose a new method, entropic chromatography, for cooling fermionic atoms in optical lattices, by exploiting the properties of the AHM. To establish this cooling strategy on a firmer basis, we also discuss the variations in temperature induced by the adiabatic tuning of interactions and hopping parameters.Comment: 16 pages, 19 fig

Effective action approach to strongly correlated fermion systems

We construct a new functional for the single particle Green's function, which is a variant of the standard Baym Kadanoff functional. The stability of the stationary solutions to the new functional is directly related to aspects of the irreducible particle hole interaction through the Bethe Salpeter equation. A startling aspect of this functional is that it allows a simple and rigorous derivation of both the standard and extended dynamical mean field (DMFT) equations as stationary conditions. Though the DMFT equations were formerly obtained only in the limit of infinite lattice coordination, the new functional described in the work, presents a way of directly extending DMFT to finite dimensional systems, both on a lattice and in a continuum. Instabilities of the stationary solution at the bifurcation point of the functional, signal the appearance of a zero mode at the Mott transition which then couples t o physical quantities resulting in divergences at the transition.Comment: 9 page

Inna Narpathu Affirmations on Impediments and Retributions

Inna Narpathu (inna forty) is a sanga tamil poetic contributions in a didactic from which belongs to one of the tamil literature Anthology patinenkilkanakku (the eighteen lesser text) written by the great poet kapilar way back in 4th century.  Inna Narpathu is the collective form of forty one venpas (metric prosody).  Inna Narpathu poem concludes wish the tamil word inna (act brings Disgrace and Sadness).  Which describing the undesirable acts individuals must refrain themselves in day today life. As these poems spells out the moral codes for all spheres. So the poem collection was entitled as ‘Inna Narpathu’. This paper emphasise the synonamised innards of the forty venpa. Which extends it’s focus on diverse topics such as friendship, domestic life, poverty, idol worship, Bhramin perspectives, offender’s nature and travel thus this paper evidently outlines the anthological aspects from Inna Narpathu.  So this paper will gives us insights and importance of social anthropology and it’s Cultural Tamil heritage crux