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 $\Delta T_c/T_c$ 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 $\gtrsim10^5$.Comment: 2 figures, 5 pages, accepted for publication in Euro. Phys. J.

Ramifications of topology and thermal fluctuations in quasi-2D condensates

We explore the topological transformation of quasi-2D Bose-Einstein condensates of dilute atomic gases, and changes in the low-energy quasiparticles associated with the geometry of the confining potential. In particular, we show the density profile of the condensate and quantum fluctuation follow the transition from a multiply to a simply connected geometry of the confining potential. The thermal fluctuations, in contrast, remain multiply connected. The genesis of the key difference lies in the structure of the low-energy quasiparticles. For which we use the Hartree-Fock-Bogoliubov, and study the evolution of quasiparticles, the dipole or the Kohn mode in particular. We, then employ the Hartree-Fock-Bogoliubov theory with the Popov approximation to investigate the density and the momentum distribution of the thermal atoms.Comment: 7 pages, 8 figure

Thermal suppression of phase separation in condensate mixtures

We examine the role of thermal fluctuations in binary condensate mixtures of dilute atomic gases. In particular, we use Hartree-Fock-Bogoliubov with Popov approximation to probe the impact of non-condensate atoms to the phenomenon of phase-separation in two-component Bose-Einstein condensates. We demonstrate that, in comparison to $T=0$, there is a suppression in the phase-separation of the binary condensates at $T\neq0$. This arises from the interaction of the condensate atoms with the thermal cloud. We also show that, when $T\neq0$ it is possible to distinguish the phase-separated case from miscible from the trends in the correlation function. However, this is not the case at $T=0$.Comment: 5 pages, 4 figure

Evolution of Goldstone mode in binary condensate mixtures

We show that the third Goldstone mode in the two-species condensate mixtures, which emerges at phase-separation, gets hardened when the confining potentials have separated trap centers. The {\em sandwich} type condensate density profiles, in this case, acquire a {\em side-by-side} density profile configuration. We use Hartree-Fock-Bogoliubov theory with Popov approximation to examine the mode evolution and density profiles for these phase transitions at $T=0$.Comment: 5 pages, 2 figures. Some part of the theory is common to arXiv:1307.5716 and arXiv:1405:6459, so that the article is self-contained for the benefit of the reader

Observation of the nuclear magnetic octupole moment of 173^{173}Yb from precise measurements of hyperfine structure in the 3P2{^3P}_2 state

We measure hyperfine structure in the metastable ${^3P}_2$ state of $^{173}$Yb and extract the nuclear magnetic octupole moment. We populate the state using dipole-allowed transitions through the ${^3P}_1$ and ${^3S}_1$ states. We measure frequencies of hyperfine transitions of the ${^3P}_2 \rightarrow {^3S}_1$ line at 770 nm using a Rb-stabilized ring cavity resonator with a precision of 200 kHz. Second-order corrections due to perturbations from the nearby ${^3P}_1$ and ${^1P}_1$ states are below 30 kHz. We obtain the hyperfine coefficients as: $A=-742.11(2)$ MHz, $B=1339.2(2)$ MHz, which represent two orders-of-magnitude improvement in precision, and $C=0.54(2)$ MHz. From atomic structure calculations, we obtain the nuclear moments: quadrupole $Q=2.46(12)$ b and octupole $\Omega=-34.4(21)$ b\,$\times \mu_N$.Comment: 5 pages, 1 figur