arXiv subjects

Rukmani Bai

Publications and source records attributed to Rukmani Bai.

15 recordsLinked to original sources

arXiv2026

Dipolar mixtures in checker-board optical bilayers

Ultra-cold dipolar mixtures in component-dependent optical potentials constitute an interesting platform for the study of the interplay between intra- and inter-component anisotropic long-range interactions. We study the particular case of binary dipolar mixtures placed in separated bilayers which are displaced in an anti-magic wavelength configuration. Using a combination of second-order perturbation theory and cluster-Gutzwiller calculations, we unveil a rich landscape of possible crystalline phases for the two components, showing that, interestingly, inter-site hopping may result, via super-exchange, in solid-into-solid transitions between different crystalline phases. These crystalline phases and the corresponding transitions can be experimentally realized using e.g. lanthanide mixtures in optical lattices.

cond-mat.quant-gas↗

arXiv2025

Miscibility-Immiscibility transition of strongly interacting bosonic mixtures in optical lattices

Interaction plays key role in the mixing properties of a multi-component system. The miscibility-immiscibility transition (MIT) in a weakly interacting mixture of Bose gases is predominantly determined by the strengths of the intra and inter-component two-body contact interactions. On the other hand, in the strongly interacting regime interaction induced processes become relevant. Despite previous studies on bosonic mixtures in optical lattices, the effects of the interaction induced processes on the MIT remains unexplored. In this work, we investigate the MIT in the strongly interacting phases of two-component bosonic mixture trapped in a homogeneous two-dimensional square optical lattice. Particularly we examine the MIT condition when both the components are in superfluid (SF), one-body staggered superfluid (OSSF), or supersolid (SS) phases. Our study uncovers that MIT condition is significantly shaped by the interplay of competing non-local intra- and inter-component density-induced tunneling effects, as well as off-site interactions. Notably, we demonstrate that the MIT condition for the staggered superfluid phase exhibits an inequality that is inverted compared to the conventional MIT condition associated with superfluid or supersolid phases driven by local contact interactions. In addition, we present the phase diagram of the Bose-Hubbard Model incorporating non-local processes, derived using a site-decoupling mean-field approach with the Gutzwiller ansatz. Our study contributes to the better understanding of miscibility properties of multi-component systems in the strongly interacting regime.

cond-mat.quant-gas↗

arXiv2024

Topological phase transition in anti-symmetric Lotka-Volterra doublet chain

We present the emergence of topological phase transition in the minimal model of two dimensional rock-paper-scissors cycle in the form of a doublet chain. The evolutionary dynamics of the doublet chain is obtained by solving the anti-symmetric Lotka-Volterra equation. We show that the mass decays exponentially towards edges and robust against small perturbation in the rate of change of mass transfer, a signature of a topological phase. For one of the configuration of our doublet chain, the mass is transferred towards both edges and the bulk is gaped. Further, we confirm this phase transition within the framework of topological band theory. For this we calculate the winding number which change from zero to one for trivial and a non-trivial topological phases respectively.

cond-mat.stat-mech↗

arXiv2024

Homogeneous Magnetic Flux in Rydberg Lattices

We present a method for generating homogeneous and tunable magnetic flux for bosonic particles in a lattice using Rydberg atoms. Our setup relies on Rydberg excitations hopping through the lattice by dipolar exchange interactions. The magnetic flux arises from complex hopping via ancilla atoms. Remarkably, the total flux within a magnetic unit cell directly depends on the ratio of the number of lattice sites to ancilla atoms, making it topologically protected to small changes in the positions of the atoms. This allows us to optimize the positions of the ancilla atoms to make the flux through the magnetic unit cell homogeneous. With this homogeneous flux, we get a topological flat band in the single-particle regime. In the many-body regime, we obtain indications of a bosonic fractional Chern insulator state at $ν= 1/2$ filling.

quant-ph↗

arXiv2022

Experimentally accessible scheme for a fractional Chern insulator in Rydberg atoms

We present a setup with Rydberg atoms for the realization of a bosonic fractional Chern insulator in artificial matter. The suggested setup relies on Rydberg atoms arranged in a honeycomb lattice, where excitations hop through the lattice by dipolar exchange interactions, and can be interpreted as hard-core bosons. The quantum many-body Hamiltonian is studied within exact diagonalization and DMRG. We identify experimentally accessible parameters where all signatures indicate the appearance of a fractional state with the same topological properties as the $ν=1/2$ bosonic Laughlin state. We demonstrate an adiabatic ramping procedure, which allows for the preparation of the topological state in a finite system, and demonstrate an experimentally accessible smoking gun signature for the fractional excitations.

quant-ph↗

arXiv2021

Quantum phases of dipolar bosons in multilayer optical lattice

We consider a minimal model to investigate the quantum phases of hardcore, polarized dipolar atoms confined in multilayer optical lattices. The model is a variant of the extended Bose-Hubbard model, which incorporates intralayer repulsion and interlayer attraction between the atoms in nearest-neighbour sites. We study the phases of this model emerging from the competition between the attractive interlayer interaction and the interlayer hopping. Our results from the analytical and cluster-Gutzwiller mean-field theories reveal that multimer formation occurs in the regime of weak intra and interlayer hopping due to the attractive interaction. In addition, intralayer isotropic repulsive interaction results in the checkerboard ordering of the multimers. This leads to an incompressible checkerboard multimer phase at half-filling. At higher interlayer hopping, the multimers are destabilized to form resonating valence-bond like states. Furthermore, we discuss the effects of thermal fluctuations on the quantum phases of the system.

cond-mat.quant-gas↗

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

Realization of a density-dependent Peierls phase in a synthetic, spin-orbit coupled Rydberg system

We experimentally realize a Peierls phase in the hopping amplitude of excitations carried by Rydberg atoms, and observe the resulting characteristic chiral motion in a minimal setup of three sites. Our demonstration relies on the intrinsic spin-orbit coupling of the dipolar exchange interaction combined with time-reversal symmetry breaking by a homogeneous external magnetic field. Remarkably, the phase of the hopping amplitude between two sites strongly depends on the occupancy of the third site, thus leading to a correlated hopping associated to a density-dependent Peierls phase. We experimentally observe this density-dependent hopping and show that the excitations behave as anyonic particles with a non-trivial phase under exchange. Finally, we confirm the dependence of the Peierls phase on the geometrical arrangement of the Rydberg atoms.

quant-ph↗

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↗

arXiv2018

Condensates in double-well potential with synthetic gauge potentials and vortex seeding

We demonstrate an enhancement in the vortex generation when artificial gauge potential is introduced to condensates confined in a double well potential. This is due to the lower energy required to create a vortex in the low condensate density region within the barrier. Furthermore, we study the transport of vortices between the two wells, and show that the traverse time for vortices is longer for the lower height of the well. We also show that the critical value of synthetic magnetic field to inject vortices into the bulk of the condensate is lower in the double-well potential compared to the harmonic confining potential.

cond-mat.quant-gas↗

arXiv2014

Theory of the electron phonon relaxation time in cuprates: Reproducing the observed temperature behaviour

We have studied the temperature dependence of the rate of energy transfer from electronic sub-system to phononic sub-system in the case of cuprates, when the system is photo-excited by a femtosecond laser pulse. In the pseudogap state, taking the electronic dispersion {\it as linear} near the nodal points of the Brillouin zone, we show that the rate of energy transfer from electronic sub-system to phononic sub-system is proportional to $T^{5}$ at lower temperatures ($T< >T_0$), here $T_0$ is the Debye temperature for cuprates. The linear electronic dispersion in the pseudogap state introduces new terms in the expression of energy transfer as given by M. I. KAGANOV et.al. \cite{kaganov}. {\it But the leading terms are the same which are found in the case of metals in the above reference.} The electron-phonon relaxation time follows $T^{-3}$ law for cuprates which agrees well with the experimental results \cite{demsar,Jdemsar}.

cond-mat.supr-con↗