arXiv subjects

D. J. Priour

Publications and source records attributed to D. J. Priour.

3 recordsLinked to original sources

arXiv2016

An Apparent Dissociation Transition in Anharmonically Bound 1D Systems

For diatomic molecules and chains bound anharmonically by interactions such a the Lennard Jones and Morse potentials, we obtain analytical expressions for thermodynamic observables including the mean bond length, thermally averaged internal energy, and the coefficient of thermal expansion. These results are valid across the shift from condensed to gas-like phases, a dissociation transition marked by a crossover with no singularities in thermodynamic variables for finite pressures, though singular behavior appears in the low pressure limit. In the regime where the thermal energy $k_{\mathrm{B}} T$ is much smaller than the dissociation energy $D$, the mean interatomic separation scales as $\langle l \rangle = R_{e} + {\mathcal B} (P R_{e}/k_{\mathrm{B}} T)^{-2} e^{-D/k_{\mathrm{B}} T} \left( D/k_{\mathrm{B}} T \right )^{1/2}$ for both the Morse and Lennard Jones potentials where $p$ is a pressure term, $R_{e}$ is the $T = 0$ bond length, and ${\mathcal B}$ is a constant specific to the potential.

cond-mat.stat-mech↗

arXiv2011

Localization in one dimensional lattices with non-nearest-neighbor hopping: Generalized Anderson and Aubry-André models

We study the quantum localization phenomena of noninteracting particles in one-dimensional lattices based on tight-binding models with various forms of hopping terms beyond the nearest neighbor, which are generalizations of the famous Aubry-André and noninteracting Anderson model. For the case with deterministic disordered potential induced by a secondary incommensurate lattice (i.e. the Aubry-André model), we identify a class of self dual models, for which the boundary between localized and extended eigenstates are determined analytically by employing a generalized Aubry-André transformation. We also numerically investigate the localization properties of non-dual models with next-nearest-neighbor hopping, Gaussian, and power-law decay hopping terms. We find that even for these non-dual models, the numerically obtained mobility edges can be well approximated by the analytically obtained condition for localization transition in the self dual models, as long as the decay of the hopping rate with respect to distance is sufficiently fast. For the disordered potential with genuinely random character, we examine scenarios with next-nearest-neighbor hopping, exponential, Gaussian, and power-law decay hopping terms numerically. We find that the higher order hopping terms can remove the symmetry in the localization length about the energy band center compared to the Anderson model. Furthermore, our results demonstrate that for the power-law decay case, there exists a critical exponent below which mobility edges can be found. Our theoretical results could, in principle, be directly tested in shallow atomic optical lattice systems enabling non-nearest-neighbor hopping.

cond-mat.dis-nn↗

arXiv2001

Core Strings and Flux Spreading Near Pinning Centers

At the nucleus of a superconducting vortex is a small, circular region where superconductivity is destroyed. Like an atomic nucleus, this core may become deformed, and such distortions can have important consequences in non-equilibrium situations. Using Ginzburg-Landau theory, we have investigated this phenomenon for vortices in the presence of artificial defects. We show that when a vortex approaches the vicinity of a defect, an abrupt transition occurs in which the vortex core develops a "string" extending to the defect boundary, while simultaneously the supercurrents and associated magnetic flux spread out and engulf the defect. The energetics of stretching the string determines the pinning behavior of the vortex. Experimental consequences of these strings are discussed.

cond-mat.supr-con↗