arXiv subjects

Tapan Mishra

Publications and source records attributed to Tapan Mishra.

At least 73 records · Page 4Linked to original sources

arXiv2016

Phases of Attractive Fermi Gases in Synthetic Dimensions

A novel way to produce quantum Hall ribbons in a cold atomic system is to use M hyperfine states of atoms in a 1D optical lattice to mimic an additional "synthetic dimension". A notable aspect here is that the SU(M) symmetric interaction between atoms manifests as "infinite ranged" along the synthetic dimension. We study the many body physics of fermions with attractive interactions in this system. We use a combination of analytical field theoretic and numerical density matrix renormalization group (DMRG) methods to reveal the rich ground state phase diagram of the system, including novel phases such as squished baryon fluids. Remarkably, changing the parameters entails unusual crossovers and transitions, e. g., we show that increasing the magnetic field (that produces the Hall effect) may convert a "ferrometallic" state at low fields to a "squished baryon superfluid" (with algebraic pairing correlations) at high fields. We also show that this system provides a unique opportunity to study quantum phase separation in a multiflavor ultracold fermionic system.

cond-mat.quant-gas↗

arXiv2015

Density-induced geometric frustration of ultra-cold bosons in optical lattices

A density-dependent gauge field may induce density-induced geometric frustration, leading to a non-trivial interplay between density modulation and frustration, which we illustrate for the particular case of ultra-cold bosons in zig-zag optical lattices with a density-dependent hopping. We show that the density-induced frustration leads in a rich landscape of quantum phases, including Mott and bond-order insulators, two-component superfluids, chiral superfluids, and partially-paired superfluids. We show as well that the density-dependent hopping results in an effective repulsive or attractive interactions, and that for the latter case the vacuum may be destabilized leading to a strong compressibility. Finally, we discuss how the predicted phases may be experimentally observed and characterized in time-of-flight measurements using their characteristic signatures in the momentum distribution.

cond-mat.quant-gas↗

arXiv2015

Frustration-induced supersolids in the absence of inter-site interactions

We discuss a mechanism for the realization of supersolids in lattices in the absence of intersite interactions that surprisingly works as well at unit filling. This mechanism, that we study for the case of the sawtooth lattice, is based on the existence of frustrated and unfrustrated plaquettes. For sufficiently large interactions and frustration the particles gather preferentially at unfrustrated plaquettes breaking spontaneously translational invariance, resulting in a supersolid. We show that for the sawtooth lattice the supersolid exists for a large region of parameters for densities above half filling. Our results open a feasible path for realizing supersolids in existing ultracold atomic gases in optical lattices without the need for long-range interactions.

cond-mat.quant-gas↗

arXiv2015

Polar molecules in frustrated triangular ladders

Polar molecules in geometrically frustrated lattices may result in a very rich landscape of quantum phases, due to the non-trivial interplay between frustration, and two- and possibly three-body inter-site interactions. In this paper, we illustrate this intriguing physics for the case of hard-core polar molecules in frustrated triangular ladders. Whereas commensurate lattice fillings result in gapped phases with bond-order and/or density-wave order, at incommensurate fillings we find chiral-, two-component-, and pair-superfluids. We show as well that, remarkably, polar molecules in frustrated lattices allow, for the first time to our knowledge, for the observation of bond-ordered supersolids.

cond-mat.quant-gas↗

arXiv2014

Quantum phases of attractive bosons on a Bose-Hubbard ladder with three-body constraint

We obtain the complete quantum phase diagram of bosons on a two-leg ladder in the presence of attractive onsite and repulsive interchain nearest-neighbor interactions by imposing the onsite three-body constraint. We find three distinct phases; namely, the atomic superfluid (ASF), dimer superfluid (DSF), and the dimer rung insulator (DRI). In the absence of the interchain nearest-neighbor repulsion, the system exhibits a transition from the ASF to the DSF phase with increasing onsite attraction. However, the presence of the interchain nearest-neighbor repulsion stabilizes a gapped DRI phase, which is flanked by the DSF phase. We also obtain the phase diagram of the system for different values of the interchain nearest-neighbor interaction. By evaluating different order parameters, we obtain the complete phase diagram and the properties of the phase transitions using the self-consistent cluster mean-field theory.

cond-mat.quant-gas↗

arXiv2014

Supersolid in a one-dimensional model of hard-core bosons

We study a system of hardcore boson on a one-dimensional lattice with frustrated next-nearest neighbor hopping and nearest neighbor interaction. At half filling, for equal magnitude of nearest and next-nearest neighbor hopping, the ground state of this system exhibits a first order phase transition from a Bond-Ordered (BO) solid to a Charge-Density-Wave(CDW) solid as a function of the nearest neighbor interaction. Moving away from half filling we investigate the system at incommensurate densities, where we find a SuperSolid (SS) phase which has concurrent off-diagonal long range order and density wave order which is unusual in a system of hardcore bosons in one dimension. Using the finite-size Density-Matrix Renormalization Group (DMRG) method, we obtain the complete phase diagram for this model.

cond-mat.quant-gas↗

arXiv2013

Hardcore bosons in a zig-zag optical superlattice

We study a system of hard-core bosons at half-filling in a one-dimensional optical superlattice. The bosons are allowed to hop to nearest and next-nearest neighbor sites producing a zig-zag geometry and we obtain the ground state phase diagram as a function of microscopic parameters using the finite-size density matrix renormalization group (FS-DMRG) method. Depending on the sign of the next-nearest neighbor hopping and the strength of the superlattice potential the system exhibits three different phases, namely the bond-order (BO) solid, the superlattice induced Mott insulator (SLMI) and the superfluid (SF) phase. When the signs of both hopping amplitudes are the same (the "unfrustrated" case), the system undergoes a transition from the SF to the SLMI at a non-zero value of the superlattice potential. On the other hand, when the two amplitudes differ in sign (the "frustrated" case), the SF is unstable to switching on a superlattice potential and also exists only up to a finite value of the next nearest neighbor hopping. This part of the phase diagram is dominated by the BO phase which breaks translation symmetry spontaneously even in the absence of the superlattice potential and can thus be characterized by a bond order parameter. The transition from BO to SLMI appears to be first order.

cond-mat.quant-gas↗

arXiv2013

Phases and phase transitions of frustrated hard-core bosons on a triangular ladder

We study hardcore bosons on a triangular ladder at half filling in the presence of a frustrating hopping term and a competing nearest neighbor repulsion $V$ which promotes crystallization. Using the finite-size density-matrix renormalization group method, we obtain the phase diagram which contains three phases: a uniform superfluid (SF), an insulating charge density wave (CDW) crystal and a bond ordered insulator (BO). We find that the transitions from SF to CDW and SF to BO are continuous in nature, with critical exponents varying continously along the phase boundaries, while the transition from CDW to BO is found to be first order. The phase diagram is also shown to contain an exactly solvable Majumdar Ghosh point, and re-entrant SF to CDW phase transitions.

cond-mat.str-el↗

arXiv2013

Google In A Photonic Lattice

The quantum version of Google PageRank has recently been investigated by various groups and shown to be quadratically faster in time than the classical PageRank algorithm. In this paper we propose the implementation of Quantum PageRank by a stochastic quantum walk of correlated photons in a photonic waveguide lattice, where we allow the density matrix to evolve according to the Lindblad-Kossakowski master equation. This yields a stationary state, the diagonal of whose density matrix gives the page ranking.

quant-ph↗

arXiv2012

Chiral Mott insulator with staggered loop currents in the fully frustrated Bose Hubbard model

Motivated by experiments on Josephson junction arrays in a magnetic field and ultracold interacting atoms in an optical lattice in the presence of synthetic orbital magnetic fields, we study the "fully frustrated" Bose-Hubbard model and quantum XY model with half a flux quantum per lattice plaquette. Using Monte Carlo simulations and the density matrix renormalization group (DMRG) method, we show that the phase diagram of such kinetically frustrated bosons displays three phases on a two-leg ladder: a weakly interacting chiral superfluid phase with staggered loop currents which spontaneously break time-reversal symmetry, a conventional Mott insulator at strong coupling, and a remarkable "Chiral Mott Insulator" (CMI) with staggered loop currents sandwiched between them at intermediate correlation. We discuss how the CMI state may be viewed as an exciton condensate or a vortex supersolid, propose and study a Jastrow variational wavefunction which captures its correlations, present DMRG results for the boson momentum distribution across the phase diagram, and consider various experimental implications of our phase diagram. Finally, we discuss generalizations to a staggered flux Bose-Hubbard model and a two-dimensional version of the CMI with edge currents in weakly coupled ladders.

cond-mat.supr-con↗

arXiv2012

Three body on-site interactions in ultracold bosonic atoms in optical lattices and superlattices

The Mott insulator-superfluid transition for ultracold bosonic atoms in an optical lattice has been extensively studied in the framework of the Bose-Hubbard model with two-body on-site interactions. In this paper, we analyze the additional effect of the three-body on-site interactions on this phase transition in optical lattice and the transitions between the various phases that arise in an optical superlattice. Using the mean-field theory and the density matrix renormalization group method, we find the phase diagrams depicting the relationships between various physical quantities in an optical lattice and superlattice. We also suggest possible experimental signatures to observe the three-body interactions.

cond-mat.quant-gas↗

arXiv2012

Bose Hubbard Model in a Strong Effective Magnetic Field: Emergence of a Chiral Mott Insulator Ground State

Motivated by experiments on Josephson junction arrays, and cold atoms in an optical lattice in a synthetic magnetic field, we study the "fully frustrated" Bose-Hubbard (FFBH) model with half a magnetic flux quantum per plaquette. We obtain the phase diagram of this model on a two-leg ladder at integer filling via the density matrix renormalization group approach, complemented by Monte Carlo simulations on an effective classical XY model. The ground state at intermediate correlations is consistently shown to be a chiral Mott insulator (CMI) with a gap to all excitations and staggered loop currents which spontaneously break time reversal symmetry. We characterize the CMI state as a vortex supersolid or an indirect exciton condensate, and discuss various experimental implications.

cond-mat.quant-gas↗

arXiv2011

Phase diagram of the half-filled one-dimensional t-V-V' model

We study the phase diagram of spinless fermions with nearest and next-nearest-neighbor interactions in one dimension utilizing the (finite-size) density-matrix renormalization group (DMRG) method. The competition between nearest and next-nearest-neighbor interactions and nearest-neighbor hopping generates four phases in this model: two charge-density-wave insulators, a Luttinger liquid phase, and a bond-order phase. We use finite-size scaling of the gap and various structure factors to determine the phase diagram.

cond-mat.str-el↗

arXiv2011

Quantum Phases of Ultracold Bosonic Atoms in a One Dimensional Optical Superlattice

We analyze various quantum phases of ultracold bosonic atoms in a periodic one dimensional optical superlattice. Our studies have been performed using the finite size density matrix renormalization group (FS-DMRG) method in the framework of the Bose-Hubbard model. Calculations have been carried out for a wide range of densities and the energy shifts due to the superlattice potential. At commensurate fillings, we find the Mott insulator and the superfluid phases as well as Mott insulators induced by the superlattice. At a particular incommensurate density, the system is found to be in the superfluid phase coexisting with density oscillations for a certain range of parameters of the system.

cond-mat.quant-gas↗

arXiv2010

Supersolid in a one-dimensional optical lattice in the presence of a harmonic trap

We study a system of ultra-cold atoms possessing long range interaction (e.g. dipole-dipole interaction) in a one dimensional optical lattice in the presence of a confining harmonic trap. We have shown that for large enough on-site and nearest neighbor interaction a supersolid phase can be stabilized, consistent with the previous Quantum Monte Carlo and DMRG results for the homogeneous system. Due to the external harmonic trap potential the supersolid phase coexists with other phases. We emphasize on the experimental signatures of the various ground state phases in the presence of a trap.

cond-mat.quant-gas↗

arXiv2009

Supersolid and solitonic phases in one-dimensional Extended Bose-Hubbard model

We report our findings on quantum phase transitions in cold bosonic atoms in a one dimensional optical lattice using the finite size density matrix renormalization group method in the framework of the extended Bose-Hubbard model. We consider wide ranges of values for the filling factors and the nearest neighbor interactions. At commensurate fillings, we obtain two different types of charge density wave phases and a Mott insulator phase. However, departure from commensurate fillings yield the exotic supersolid phase where both the crystalline and the superfluid orders coexist. In addition, we obtain signatures for solitary waves and also superfluidity.

cond-mat.quant-gas↗

arXiv2009

Induced supersolidity in a normal and hardcore boson mixture

It is well known that the supersolid form of matter can arise in a single species of cold bosonic atoms in an optical lattice due to long range interactions. We present a scenario where a supersolid is induced in one of the components of a mixture of two species bosonic atoms where there is no long range interactions. We study a system of normal and hardcore boson mixture with only the former possessing long range interactions. We consider three cases: the first where the total density is commensurate and the other two where they are incommensurate . By suitable choices of the densities and the interaction strengths of the atoms, we predict that the charge density wave and the supersolid orders can be induced in the hardcore species as a result of the competing interatomic interactions.

cond-mat.quant-gas↗

arXiv2008

Signatures of the superfluid to Mott insulator transition in cold bosonic atoms in a one dimensional optical lattice

We study the Bose-Hubbard model using the finite size density matrix renormalization group method. We obtain for the first time a complete phase diagram for a system in the presence of a harmonic trap and compare it with that of the homogeneous system. To realize the transition from the superfluid to the Mott insulator phase we investigate different experimental signatures of these phases in quantities such as momentum distribution, visibility, condensate fraction and the total number of bosons at a particular density. The relationships between the various experimental signatures and the phase diagram are highlighted.

cond-mat.other↗