The static properties, i.e., existence and stability, as well as the quench-induced dynamics of nonlinear excitations of the vortex-bright type appearing in two-dimensional harmonically confined spin-1 Bose-Einstein condensates are investigated. Line
arly stable vortex-bright-vortex and bright-vortex-bright solutions arise in both antiferromagnetic and ferromagnetic spinor gases upon quadratic Zeeman energy shift variations. The precessional motion of such coherent structures is subsequently monitored dynamically. Deformations of the above configurations across the relevant transitions are exposed and discussed in detail. It is further found that stationary states involving highly quantized vortices can be realized in both settings. Spatial elongations, precessional motion and spiraling of the nonlinear excitations when exposed to finite temperatures and upon crossing the distinct phase boundaries, via quenching of the quadratic Zeeman coefficient, are unveiled. Spin-mixing processes triggered by the quench lead, among others, to changes in the waveform of the ensuing configurations. Our findings reveal an interplay between pattern formation and spin-mixing processes being accessible in contemporary cold atom experiments.
Quantum fluctuations and related phase transitions are of current interest from the viewpoint of fundamental physics and technological applications. Quantum phase implies a region where the quantum fluctuations of energy scale $hbaromega$ dominates o
ver the thermal energy $k_B$T. Presence of quantum phase leads to unconventional and unexpected physical phenomena like Kondo effect, non-Fermi liquids, ordered magnetic state, and Fermi liquids, etc. In this framework, Ce-based metallic compounds, exhibiting correlated electron phenomena, emerged as prototypical systems to study the various quantum phases. In these systems considerable efforts have been made, both experimentally and theoretically, to overcome the problems related to the comprehensive understanding of correlated quantum phases. In this article, various aspects related to quantum phases in CeNiGe2, CeGe and CeAlGe are summarized, mainly focusing on the structural and physical properties.
We observe experimentally the spontaneous formation of star-shaped surface patterns in driven Bose-Einstein condensates. Two-dimensional star-shaped patterns with $l$-fold symmetry, ranging from quadrupole ($l=2$) to heptagon modes ($l=7$), are param
etrically excited by modulating the scattering length near the Feshbach resonance. An effective Mathieu equation and Floquet analysis are utilized, relating the instability conditions to the dispersion of the surface modes in a trapped superfluid. Identifying the resonant frequencies of the patterns, we precisely measure the dispersion relation of the collective excitations. The oscillation amplitude of the surface excitations increases exponentially during the modulation. We find that only the $l=6$ mode is unstable due to its emergent coupling with the dipole motion of the cloud. Our experimental results are in excellent agreement with the mean-field framework. Our work opens a new pathway for generating higher-lying collective excitations with applications, such as the probing of exotic properties of quantum fluids and providing a generation mechanism of quantum turbulence.
We unravel the ground state properties and the non-equilibrium quantum dynamics of two bosonic impurities immersed in an one-dimensional fermionic environment by applying a quench of the impurity-medium interaction strength. In the ground state, the
impurities and the Fermi sea are phase-separated for strong impurity-medium repulsions while they experience a localization tendency around the trap center for large attractions. We demonstrate the presence of attractive induced interactions mediated by the host for impurity-medium couplings of either sign and analyze the competition between induced and direct interactions. Following a quench to repulsive interactions triggers a breathing motion in both components, with an interaction dependent frequency and amplitude for the impurities, and a dynamical phase-separation between the impurities and their surrounding for strong repulsions. For attractive post-quench couplings a beating pattern owing its existence to the dominant role of induced interactions takes place with both components showing a localization trend around the trap center. In both quench scenarios, attractive induced correlations are manifested between non-interacting impurities and are found to dominate the direct ones only for quenches to attractive couplings.
A Faraday-wave-like parametric instability is investigated via mean-field and Floquet analysis in immiscible binary Bose-Einstein condensates. The condensates form a so-called textit{ball-shell} structure in a two-dimensional harmonic trap. To trigge
r the dynamics, the scattering length of the core condensate is periodically modulated in time. We reveal that in the dynamics the interface becomes unstable towards the formation of oscillating patterns. The interface oscillates sub-harmonically exhibiting an $m$-fold rotational symmetry that can be controlled by maneuvering the amplitude and the frequency of the modulation. Using Floquet analysis we are able to predict the generated interfacial tension of the mixture and derive a dispersion relation for the natural frequencies of the emergent patterns. A heteronuclear system composed of $^{87}$Rb-$^{85}$Rb atoms can be used for the experimental realization of the phenomenon, yet our results are independent of the specifics of the employed atomic species {and of the parameter at which the driving is applied.
YBaCuFeO5 is one of the interesting multiferroic compounds, which exhibits magnetic ordering and dielectric anomaly above 200 K. Partial substitution of Fe with other magnetic and non-magnetic ion affects the magnetic and the structural properties of
the system. We report detailed investigation of structural, magnetic and dielectric properties of YBaCuFe0.85M0.15O5 (M=Co, Ni and Ga). We observed that the partial replacement of Ni and Co in place of Fe, results in magnetic dilution and broadening of the magnetic transition and shifting towards lower temperature. The replacement of Fe with non-magnetic Ga also results in shifting of the magnetic transition to the lower temperature side. The observed dielectric relaxation behavior in these compounds is due to the charge carrier hoping. This study highlights the impacts of magnetic and non-magnetic doping at the magnetic site on magnetic and dielectric properties in layered perovskite compound YBaCuFeO5.
The layered perovskite compounds are interesting due to their intriguing physical properties. In this article we report the structural, magnetic and dielectric properties of LnBaCuFeO5 (Ln=Nd, Eu, Gd, Ho and Yb). The structural parameters decrease fr
om Nd to Yb due to the decrease in the ionic radii of the rare earth ions. An antiferromagnetic transition is observed for EuBaCuFeO5 near 120 K along with the glassy dynamics of the electric dipoles below 100 K. The magnetic transition is absent in other compounds, which may be due to the dominance of the magnetic moment of the rare earth ions. The dielectric constant does not show any anomaly, except in the case of HoBaCuFeO5 where it shows a weak frequency dependence around 54 K. These compounds show a significant enhancement of dielectric constant at high temperatures which have been attributed to Maxwell-Wagner effect. However, no significant magneto-dielectric coupling has been observed in these layered perovskites.
We report structural, magnetic and dielectric properties of layered perovskite materials LnBaCuFeO5 (Ln = La and Lu). LaBaCuFeO5 shows magnetic cluster glass behavior below 60 K owing to the competing ferromagnetic and antiferromagnetic exchange inte
ractions. Glassy dynamics of electric dipoles has also been observed in the vicinity of the magnetic glass transition temperature. The presence of significant coupling between spin and polar degrees of freedom results in the multiglass feature in LaBaCuFeO5. The LuBaCuFeO5 compound undergoes YBaCuFeO5 like commensurate to incommensurate antiferromagnetic transition at 175 K. Large magnetic irreversibility below 17 K in this compound suggests the presence of strong spin anisotropy. In addition, in this compound the interaction between the dipoles is not strong enough, which results in the absence of glassy dynamics of electric dipoles. The contrasting behavior of two compounds is possibly due to variation in the ferromagnetic and antiferromagnetic interactions along c-axis, which is the manifestation of structural modification arising out of the difference in the ionic radii of La and Lu.
We report a systematic investigation of the magnetic and magnetocaloric properties of Dy5Pd2 and Dy5PdNi. Our study on these compounds gave evidence that they exhibit complex magnetic behaviour along with the presence of glass-like magnetic phase. Fu
rthermore, in these compounds both second order and first order phase transitions were present, which were validated through Arrott plots and Landau parameter analysis. AC susceptibility along with time dependent magnetisation study has confirmed the presence of double cluster glass-like freezing in both Dy5Pd2 and Dy5PdNi. These compounds show significant value of isothermal entropy change and relative cooling power and these values increased with Ni substitution. Beside conventional magnetocaloric effect, inverse magnetocaloric effect was noted in these compounds, which might arise due to the presence of complex non-equilibrium magnetic state. Along with these compounds a universal characteristic curve involving two other members of R5Pd2 family i.e. Er5Pd2 and Tb5Pd2 was constructed. The master curve reaffirmed the presence of both second and first order magnetic phase transition in such compounds which were in analogy to our results of Arrott plots and Landau parameter analysis. Additionally, magnetic entropy change followed the power law and the obtained exponent values indicated the presence of mixed magnetic interactions in these compounds.
We report the evolution of structural, magnetic and dielectric properties due to partial substitution of Ba by Sr in the high temperature multiferroic YBaCuFeO5. This compound exhibits ferroelectric and antiferromagnetic transitions around 200 K and
these two phenomena are presumed to be coupled with each other. Our studies on magnetic and dielectric properties of the YBa1-xSrxCuFeO5 (x = 0.0, 0.25 and 0.5) show that substitution of Sr shifts magnetic transition towards higher temperature whereas dielectric transition to lower temperature. These results points to the fact that magnetic and dielectric transitions get decoupled as a result of chemical pressure in form of Sr substitution. The nature of magnetodielectric coupling changes across the series with the presence of higher order coupling terms. Additionally in these compounds glassy dynamics of electric dipoles is observed at low temperatures.
