arXiv subjects

K. Suthar

Publications and source records attributed to K. Suthar.

11 recordsLinked to original sources

arXiv2020

Segregated quantum phases of dipolar bosonic mixtures in two-dimensional optical lattices

We identify the quantum phases in a binary mixture of dipolar bosons in two-dimensional optical lattices. Our study is motivated by the recent experimental realization of binary dipolar condensate mixtures of Er-Dy [Phys. Rev. Lett. 121, 213601 (2018)]. We model the system by using the extended two-species Bose-Hubbard model and calculate the ground-state phase diagrams by using mean-field theory. For selected cases we also obtain analytical phase boundaries by using the site-decoupled mean-field theory. For comparison we also examine the phase diagram of two-species Bose-Hubbard model. Our results show that the quantum phases with the long-range intraspecies interaction phase separate with no phase ordering. The introduction of the long-range interspecies interaction modifies the quantum phases of the system. It leads to the emergence of phase-separated quantum phases with phase ordering. The transition from the phase-separated quantum phases without phase ordering to phase ordered ones breaks the inversion symmetry.

cond-mat.quant-gas↗

arXiv2020

Supersolid phase of the extended Bose-Hubbard model with an artificial gauge field

We examine the zero and finite temperature phase diagrams of soft-core bosons of the extended Bose-Hubbard model on a square optical lattice. To study various quantum phases and their transitions we employ single-site and cluster Gutzwiller mean-field theory. We have observed that the Mott insulator phase vanishes above a critical value of nearest-neighbour interaction and the supersolid phase occupies a larger region in the phase diagram. We show that the presence of artificial gauge field enlarges the domain of supersolid phase. The finite temperature destroys the crystalline structure of the supersolid phase and thereby favours normal fluid to superfluid phase transition. The presence of an envelope harmonic potential demonstrates coexistence of different phases and at $z~k_{B}T\geqslant V$, thermal energy comparable and higher to the long-range interaction energy, the supersolidity of the system is destroyed.

cond-mat.quant-gas↗

arXiv2020

Characteristic temperature for the immiscible-miscible transition of binary condensates in optical lattices

We study a two-species Bose-Einstein condensates confined in quasi-two-dimensional (quasi-2D) optical lattices at finite temperatures, employing the Hartree-Fock-Bogoliubov theory with the Popov approximation. We examine the role of thermal fluctuations on the ground-state density distributions, and the quasiparticle mode evolution. At zero temperature, the geometry of the ground-state in the immiscible domain is side-by-side. Our results show that the thermal fluctuations enhance the miscibility of the condensates, and at a characteristic temperature the system becomes miscible with rotationally symmetric overlapping density profiles. This immiscible-miscible transition is accompanied by a discontinuity in the excitation spectrum, and the low-lying quasiparticle modes such as slosh mode becomes degenerate at the characteristic temperature.

cond-mat.quant-gas↗

arXiv2019

Quantum Hall states for $α= 1/3$ in optical lattices

We examine the quantum Hall (QH) states of the optical lattices with square geometry using Bose-Hubbard model (BHM) in presence of artificial gauge field. In particular, we focus on the QH states for the flux value of $α= 1/3$. For this, we use cluster Gutzwiller mean-field (CGMF) theory with cluster sizes of $3\times 2$ and $3\times 3$. We obtain QH states at fillings $ν= 1/2, 1, 3/2, 2, 5/2$ with the cluster size $3\times 2$ and $ν= 1/3, 2/3, 1, 4/3, 5/3, 2, 7/3, 8/3$ with $3\times 3$ cluster. Our results show that the geometry of the QH states are sensitive to the cluster sizes. For all the values of $ν$, the competing superfluid (SF) state is the ground state and QH state is the metastable state.

cond-mat.quant-gas↗

arXiv2019

Quantum phases of tilted dipolar bosons in two-dimensional optical lattice

We consider a minimal model to describe the quantum phases of ultracold dipolar bosons in two-dimensional (2D) square optical lattices. The model is a variation of the extended Bose-Hubbard model and apt to study the quantum phases arising from the variation in the tilt angle $θ$ of the dipolar bosons. At low tilt angles $0^{\circ}\leqslantθ\apprle25^{\circ}$, the ground state of the system are phases with checkerboard order, which could be either checkerboard supersolid or checkerboard density wave. For high tilt angles $55^{\circ}\apprgeθ\apprge35^{\circ}$, phases with striped order of supersolid or density wave are preferred. In the intermediate domain $25^{\circ}\apprleθ\apprle35^{\circ}$ an emulsion or SF phase intervenes the transition between the checkerboard and striped phases. The attractive interaction dominates for $θ\apprge55^{\circ}$, which renders the system unstable and there is a density collapse. For our studies we use Gutzwiller mean-field theory to obtain the quantum phases and the phase boundaries. In addition, we calculate the phase boundaries between an incompressible and a compressible phase of the system by considering second order perturbation analysis of the mean-field theory. The analytical results, where applicable, are in excellent agreement with the numerical results.

cond-mat.quant-gas↗

arXiv2019

Enhancement of the Bose glass phase in the presence of an artificial gauge field

We examine the effects of an artificial gauge field and finite temperature in a two-dimensional disordered Bose-Hubbard model. The disorder considered is diagonal and quenched in nature. A signature of disorder in the Bose-Hubbard model is the Bose glass phase. Our work shows that the introduction of an artificial gauge field enhances the domain of the Bose glass phase in the phase diagram. Most importantly, the size of the domain can be tuned with the strength of the artificial gauge field. The introduction of the finite temperature effects is essential to relate theoretical results with the experimental realizations. For our studies we use the single site and cluster Gutzwiller mean-field theories. The results from the latter are more reliable as it better describes the correlation effects. Our results show that the Bose glass phase has a larger domain with the latter method.

cond-mat.quant-gas↗

arXiv2018

Bosonic quantum Hall states in single-layer two-dimensional optical lattices

Quantum Hall (QH) states of 2D single layer optical lattices are examined using Bose-Hubbard model (BHM) in presence of artificial gauge field. We study the QH states of both the homogeneous and inhomogeneous systems. For the homogeneous case we use cluster Gutzwiller mean field (CGMF) theory with cluster sizes ranging from $2\times 2$ to $5\times 5$. We, then, consider the inhomogeneous case, which is relevant to experimental realization. In this case, we use CGMF and exact diagonalization (ED). The ED studies are using lattice sizes ranging from $3\times 3$ to $4\times 12$. Our results show that the geometry of the QH states are sensitive to the magnetic flux $α$ and cluster sizes. For homogeneous system, among various combinations of $1/5\leqslant α\leqslant 1/2$ and filling factor $ν$, only the QH state of $α=1/4$ with $ν=1/2$, $1$, $3/2$ and $2$ occur as ground states. For other combinations, the competing superfluid (SF) state is the ground state and QH state is metastable. For BHM with envelope potential all the QH states observed in homogeneous system exist for box potentials, but none for the harmonic potential. The QH states also persist for very shallow Gaussian envelope potential. As a possible experimental signature we study the two point correlations of the QH and SF states.

cond-mat.quant-gas↗

arXiv2016

Optical lattice influenced geometry of quasi-2D binary condensates and quasiparticle spectra

We explore the collective excitations of optical lattices filled with two-species Bose-Einstein condensates (TBECs). We use a set of coupled discrete nonlinear Schrödinger equations to describe the system, and employ Hartree-Fock-Bogoliubov (HFB) theory with the Popov approximation to analyze the quasiparticle spectra at zero temperature. The ground state geometry, evolution of quasiparticle energies, structure of quasiparticle amplitudes, and dispersion relations are examined in detail. The trends observed are in stark contrast to the case of TBECs only with a harmonic confining potential. One key observation is the quasiparticle energies are softened as the system is tuned towards phase separation, but harden after phase separation and mode degeneracies are lifted.

cond-mat.quant-gas↗

arXiv2014

Fluctuation driven topological transition of binary condensates in optical lattices

We show the emergence of a third Goldstone mode in binary condensates at the phase-separation in quasi-1D optical lattices. We develop the coupled discrete nonlinear Schrödinger equations (DNLSEs) using Hartree-Fock-Bogoliubov theory with Popov approximation in the Bose-Hubbard model to investigate the mode evolution at zero temperature. In particular, as the system is driven from miscible to immiscible phase. We demonstrate that the position swapping of the species in $^{87}$Rb-$^{85}$Rb system is accompanied by a discontinuity in the excitation spectrum. Our results show that in quasi-1D optical lattices, the presence of the fluctuations dramatically change the geometry of the ground state density profile of TBEC.

cond-mat.quant-gas↗

arXiv2014

Vortex reconnections between coreless vortices in binary condensates

Vortex reconnections plays an important role in the turbulent flows associated with the superfluids. To understand the dynamics, we examine the reconnections of vortex rings in the superfluids of dilute atomic gases confined in trapping potentials using Gross-Petaevskii equation. Furthermore we study the reconnection dynamics of coreless vortex rings, where one of the species can act as a tracer.

cond-mat.quant-gas↗

arXiv2014

Acoustic radiation from vortex-barrier interaction in atomic Bose-Einstein condensate

We examine the dynamics of a vortex dipole in the Bose-Einstein condensates (BECs) of trapped dilute atomic gases at zero temperature in the presence of a Gaussian barrier potential. The density-anisotropy induced by the barrier enhances the acoustic radiation from the vortex dipole. This is due to the deviation of the condensate density from the equipotential curves and variation in the curvature of the vortex dipole trajectory. Due to the acoustic radiation, the vortex dipole dissipates energy and spirals towards the edge of the condensate. As a result, we observe an increase in the vortex-antivortex annihilation events. To examine the effect of the Gaussian barrier, we estimate the correction to the Thomas-Fermi condensate density using perturbation expansion method and the results are in very good agreement with the numerical results.

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