arXiv subjects

D. Angom

Publications and source records attributed to D. Angom.

63 records · Page 4Linked to original sources

arXiv2009

Properties from relativistic coupled-cluster without truncation: hyperfine constants of $^{25}{\rm Mg}^+$, $^{43}{\rm Ca}^+ $, $^{87}{\rm Sr}^+ $ and $^{137}{\rm Ba}^+$

We demonstrate an iterative scheme for coupled-cluster properties calculations without truncating the dressed properties operator. For validation, magnetic dipole hyperfine constants of alkaline Earth ions are calculated with relativistic coupled-cluster and role of electron correlation examined. Then, a detailed analysis of the higher order terms is carried out. Based on the results, we arrive at an optimal form of the dressed operator. Which we recommend for properties calculations with relativistic coupled-cluster theory.

physics.atom-ph↗

arXiv2009

Ground State Geometry of Binary Condensates in Axisymmetric Traps

We show that the ground state interface geometry of binary condensates in the phase separated regime undergoes a smooth transition from planar to ellipsoidal to cylindrical geometry. This occurs for condensates with repulsive interactions as the trapping potential is changed from prolate to oblate. The correct ground state geometry emerges when the interface energy is included in the energy minimization. Where as energy minimization based on Thomas-Fermi approximation gives incorrect geometry.

cond-mat.quant-gas↗

arXiv2009

Rayleigh-Taylor instability of binary condensates

We propose a scheme to initiate and examine Rayleigh-Taylor instability in the two species Bose-Einstein condensates. We identify $^{85}$Rb-$^{87}$Rb mixture as an excellent candidate to observe it experimentally. The instability is initiated by tuning the $^{85}$Rb-$^{85}$Rb interaction through magnetic Feshbach resonance. We show that the observable signature of the instability is the damping of the radial oscillation. This would perhaps be one of the best controlled experiments on Rayleigh-Taylor instability. We also propose a semi analytic scheme to determinate stationary state of binary condensates with the Thomas-Fermi approximation for the axis symmetric traps.

cond-mat.quant-gas↗

arXiv2009

Relativistic coupled-cluster calculations of $^{20}$Ne, $^{40}$Ar, $^{84}$Kr and $^{129}$Xe: correlation energies and dipole polarizabilities

We have carried out a detailed and systematic study of the correlation energies of inert gas atoms Ne, Ar, Kr and Xe using relativistic many-body perturbation theory and relativistic coupled-cluster theory. In the relativistic coupled-cluster calculations, we implement perturbative triples and include these in the correlation energy calculations. We then calculate the dipole polarizability of the ground states using perturbed coupled-cluster theory.

physics.atom-ph↗

arXiv2009

Probing CP violation with the electric dipole moment of atomic mercury

The electric dipole moment of atomic $^{199}$Hg induced by the nuclear Schiff moment and tensor-pseudotensor electron-nucleus interactions has been calculated. For this, we have developed and employed a novel method based on the relativistic coupled-cluster theory. The results of our theoretical calculations combined with the latest experimental result of $^{199}$Hg electric dipole moment, provide new bounds on the T reversal or CP violation parameters $θ_{\rm QCD}$, the tensor-pseudotensor coupling constant $C_T$ and $(\widetilde{d}_u - \widetilde{d}_d)$. This is the most accurate calculation of these parameters to date. We highlight the the crucial role of electron correlation effects in their interplay with the P,T violating interactions. Our results demonstrate substantial changes in the results of earlier calculations of these parameters which can be attributed to the more accurate inclusion of important correlation effects in the present work.

physics.atom-ph↗

arXiv2008

Pairing in spin polarized two-species fermionic mixtures with mass asymmetry

We discuss on the pairing mechanism of fermions with mismatch in their fermi momenta due to a mass asymmetry. Using a variational ansatz for the ground state we also discuss the BCS -BEC crossover of this system. It is shown that the breached pairing solution with a single fermi surface is stable in the BEC regime. We also include the temperatures effect on the fermion pairing within an approximation that is valid for temperatures much below the critical temperature.

cond-mat.supr-con↗

arXiv2008

p-wave phase shift and scattering length of $^6$Li

We have calculated the p-wave phase shifts and scattering length of $^6$Li. For this we solve the $p$ partial wave Schrödinger equation and analyze the validity of adopting the semiclassical solution to evaluate the constant factors in the solution. Unlike in the $s$ wave case, the semiclassical solution does not provide unique value of the constants. We suggest an approximate analytic solution, which provides reliable results in special cases. Further more, we also use the variable phase method to evaluate the phase shifts. The p-wave scattering lengths of $^{132}$Cs and $^{134}$Cs are calculated to validate the schemes followed. Based on our calculations, the value of the $p$ wave scattering length of $^6$Li is $-45a_o$.

physics.atom-ph↗

arXiv2007

Critical Temperature for Bose-Einstein condensation in quartic potentials

The quartic confining potential has emerged as a key ingredient to obtain fast rotating vortices in BEC as well as observation of quantum phase transitions in optical lattices. We calculate the critical temperature $T_c$ of bosons at which normal to BEC transition occurs for the quartic confining potential. Further more, we evaluate the effect of finite particle number on $T_c$ and find that $ΔT_c/T_c$ is larger in quartic potential as compared to quadratic potential for number of particles $ < 10^5$. Interestingly, the situation is reversed if the number of particles is $\gtrsim10^5$.

physics.atom-ph↗

arXiv2004

Strength functions, entropies and duality in weakly to strongly interacting fermionic systems

We revisit statistical wavefunction properties of finite systems of interacting fermions in the light of strength functions and their participation ratio and information entropy. For weakly interacting fermions in a mean-field with random two-body interactions of increasing strength $λ$, the strength functions $F_k(E)$ are well known to change, in the regime where level fluctuations follow Wigner's surmise, from Breit-Wigner to Gaussian form. We propose an ansatz for the function describing this transition which we use to investigate the participation ratio $ξ_2$ and the information entropy $S^{\rm info}$ during this crossover, thereby extending the known behavior valid in the Gaussian domain into much of the Breit-Wigner domain. Our method also allows us to derive the scaling law for the duality point $λ= λ_d$, where $F_k(E)$, $ξ_2$ and $S^{\rm info}$ in both the weak ($λ=0$) and strong mixing ($λ= \infty$) basis coincide as $λ_d \sim 1/\sqrt{m}$, where $m$ is the number of fermions. As an application, the ansatz function for strength functions is used in describing the Breit-Wigner to Gaussian transition seen in neutral atoms CeI to SmI with valence electrons changing from 4 to 8.

quant-ph↗