Biomedical subjects

Indubala I Satija

Publications and source records attributed to Indubala I Satija.

5 recordsLinked to original sources

PubMed2006

Metal-insulator transition revisited for cold atoms in non-Abelian gauge potentials.

We discuss the possibility of realizing metal-insulator transitions with ultracold atoms in two-dimensional optical lattices in the presence of artificial gauge potentials. For Abelian gauges, such transitions occur when the magnetic flux penetrating the lattice plaquette is an irrational multiple of the magnetic flux quantum. Here we present the first study of these transitions for non-Abelian U(2) gauge fields. In contrast to the Abelian case, the spectrum and localization transition in the non-Abelian case is strongly influenced by atomic momenta. In addition to determining the localization boundary, the momentum fragments the spectrum. Other key characteristics of the non-Abelian case include the absence of localization for certain states and satellite fringes around the Bragg peaks in the momentum distribution and an interesting possibility that the transition can be tuned by the atomic momenta.

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PubMed2005

Topological singularities and transport in kicked Harper model.

Quasienergy spectrum of kicked Harper model is found to exhibit a series of diabolic crossings. These conical degeneracies reside mostly on the symmetry line of its two-dimensional parameter space and their locations are found to coincide with the local maxima of the kinetic energy of the kicked system. Additionally, there are exceptional point singularities, that are found by analytically continuing the kicking parameter in the complex plane. The location of these singularities appear to be correlated with the localization of the quantum wave packet. These studies suggest a correlation between the transport and the topological characteristics of the system.

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PubMed2002

Quantum response to classical transitions.

The richness and complexity of two-dimensional parameter space of the kicked Harper model is exploited to demonstrate quantum fingerprints of all classical transitions. The quantum system appears to follow the corresponding classical system in parameter but not in time in the localized, critical as well as in the ballistic regimes. Therefore, the relationship between quantum and classical systems appears to be universal when measured by their response to parameter changes. Additionally, a rather intriguing feature of quantum eigenstates is a set of critical points sprinkled in the regime where the classical dynamics is diffusive. These are the boundary points of the ballistic (localized) patches in the localized (ballistic) regime that survive in the semiclassical limit.

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PubMed2002

planck-->0 and classical-quantum correspondence in the kicked Harper model.

We investigate classical-quantum correspondence for the kicked Harper model for extremely small values of the Planck constant (planck). In the asymmetric case a pure quantum state shows a clear signature of classical diffusive as well as superdiffusive transitions asymptotically independent of planck. However, for the symmetric case, the planck independent behavior occurs only for the renormalized parameter (-)K=K/(2planck) with intriguing features such as a sharp transition from integrable to nonintegrable transport at (-)K=pi/2, a series of transitions at multiples of pi, and the periodicity of the transmission probability. We suggest that even as planck-->0, the quantum dynamics is influenced by cantori and additional features emerge in their absence.

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PubMed2002

Non-Hermiticity in a kicked model: decoherence and the semiclassical limit.

We study the effects of non-Hermitian perturbations on a quantum kicked model exhibiting a localization transition. Using an exact renormalization scheme, we show that the critical line separating the extended and localized phases approaches its semiclassical limit as the imaginary part of the kicking parameter is steadily increased. Further, the metastability of the quantum states appears to be directly correlated with the deviation between the semiclassical and quantum results. This direct evidence of quantum-classical correspondence suggests that decoherence may be usefully modeled by non-Hermitian perturbations.

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