arXiv subjects

Sujit Sarkar

Publications and source records attributed to Sujit Sarkar.

50 records · Page 3Linked to original sources

arXiv2009

Josephson decoupling phase in inhomoheneous arrays of superconducting quantum dots

We present a study of quantum phase analysis of inhomogeneous and homogeneous arrays of superconducting quantum dots (SQD). We observe the existance of Josephson decouple (JD) phase only at the half filling for inhomogeneous array of SQD due to the fluctuation of Josephson couplings over the sites at half filling. In JD phase superconductivity disappears even in the absence of Coulomb blockade phase. We also observe that fluctuation of on-site Coulomb charging energy produces the relevant coupling term that yields Coulomb blockade gapped phase. The presence of nearest-neighbor and next-nearest-neighbor Coulomb interaction yields the same physics for inhomogeneous and homogeneous SQD.

cond-mat.mes-hall↗

arXiv2009

Solution of the asymmetric double sine-Gordon equation

We present solutions of asymmetric double sine-Gordon equation (DSGE) of an infinite system based on Mobius transformation and numerical exercise. This method is able to give the forms of the solutions for all the region on the ϕ-ηparameter plane where ϕis an additional phase and ηis the ratio of the magnitudes of two sine terms. We are able to show how the deconfinement occurs near ϕ=(1/2+n)πand ϕ=n pi. and also find the solution for all values of ϕ. We predict different kind of solutions and transitions among them in different parts of the parameter space of this equation.

cond-mat.str-el↗

arXiv2008

Quantum Phases of Long Range 1-D Bose-Hubbard Model: Field Theoretic and DMRG Study at Different Densities

We use Abelian Bosonization and density matrix renormalization group method to study the effect of density on quantum phases of long range 1-D Bose-Hubbard model. We predict the existence of supersolid phase and also other quantum phases for this system. We have analyzed the role of long range interaction parameter on solitonic phase near half filling. We discuss the effect of dimerization in nearest neighbor hopping and interaction terms on the plateau phase at the half filling.

cond-mat.stat-mech↗

arXiv2008

Quantum spin pump on a finite antiferromagnetic chain through bulk states

We studied the possibility of the spin pump in a S=1/2 antiferromagnetic chain. The spin chain is mapped into a fermion system and bosonization is utilized to transform the equation of motion to a sine-Gordon equation. The sine-Gordon equation on a finite chain with different boundary conditions is solved. Among numerous solutions, the static soliton is compatible with the original physical system. By varying adiabatically a angle in the phase space composed of applied electric and magnetic fields, the spin states change between the Neel state and dimer state and a quantized spin is transported by the bulk state from one end of the system to the other.

cond-mat.str-el↗

arXiv2008

Quantum phase diagram of a spin-1/2 antiferromagnetic chain with magnetic impurity

We present the renormalization group (RG) flow diagram of a spin-half antiferromagnetic chain with magnetic impurity and one altered link. In this two parameters (competing interactions) model, one can find the complex phase diagram with many interesting fixed points. There is no evidence of intermediate stable fixed point in weak coupling phase. It may arise at the strong coupling phase. Depending on the strength of couplings the phases correspond either to a decoupled spin with Curie law behavior or a logarithmically diverging impurity susceptibility as in the two channel Kondo problem.

cond-mat.mes-hall↗

arXiv2008

Fractionally Quantized Cooper Pair Stair Case in Superconducting Quantum Dots

We study clean superconducting quantum dots (SQD) and also site dependent Josephson couplings, on site charging energies and the intersite interactions in presence of gate voltage. We predict the existence of different fractionally quantized Cooper pair stair case with many interesting physical properties. The appearance of stair case is not only due to the Coulomb blocked phenomena but also for the site dependent Josephson couplings. We also explain physically the absence of other fractionally quantized Cooper pair stair case. The physics of fractionally quantized Cooper pair stair case has close resemblance with the fractionally quantized magnetization plateau of a spin chain system under a magnetic field.

cond-mat.mes-hall↗

arXiv2008

Adiabatic Cooper-Pair Pumping in a Linear Array of Cooper Pair Boxes

We present a study of adiabatic Cooper pair pumping in one dimensional array of Cooper pair boxes. We do a detailed theoretical analysis of an experimentally realizable stabilized charge pumping scheme in a linear array of Cooper pair boxes. Our system is subjected to synchronized flux and voltage fields and travel along a loop which encloses their critical ground state of the system in the flux-voltage plane. The locking potential in the sine-Gordon model slides and changes its minimum which yields the Cooper pair pumping. Our analytical methods are the Berry phase analysis and Abelian bosonization studies.

cond-mat.mes-hall↗

arXiv2008

Length-Scale Dependent Superconductor-Insulator Quantum Phase Transition in One Dimension

We study the dissipation physics of one dimensional mesoscopic superconducting quantum interference device array by using the field-theoretical renormalization group method. We observe length scale dependent superconductor-insulator quantum phase transition at very low temperature and also observe the dual behaviour of the system for the higher and lower values of magnetic field. At a critical magnetic field, we also observe a critical behaviour where the resistance is independent of length.

cond-mat.mes-hall↗

arXiv2008

Effect of strong correlation on the study of renormalization group flow diagram for Kondo effect in a interacting quantum wire

We present the study of Kondo effect in an interacting quantum wire. We mainly emphasis the effect of strong electronic correlations in the study of renormalization group flow diagram and the stability analysis of fixed points for both magnetic and nonmagnetic impurities. We observe that the behavior of the system is either in the single channel or in the two channel Kondo effect depending on the initial values of coupling constants and strong correlations.

cond-mat.mes-hall↗

arXiv2008

Quantum spin pumping at fractionally quantized magnetization state for a system with competing exchange interactions

We study the quantum spin pumping of an antiferromagnetic spin-1/2 chain with competing exchange interactions. We show that spatially periodic potential modulated in space and time acts as a quantum spin pump. In our model system, an applied electric field causes a spin gap to its critical ground state by introducing bond-alternation exchange interactions. We study quantum spin pumping at different quantized magnetization states and also explain physically the presence and absence of quantum spin pumping at different fractionally quantized magnetization states.

cond-mat.str-el↗

arXiv2008

Quantum Phase Analysis of Extended Bose-Hubbard Model

We have obtained the quantum phase diagram of one dimensional extended Bose-Hubbard model using the density-matrix renormalization group and Abelian bosonization methods for different commensurabilities. We describe the nature of different quantum phases at the charge degeneracy point. We find a direct phase transition from Mott insulating phase to superconducting phase for integer band fillings of bosons. We predict explicitly the presence of two kinds of repulsive Luttinger liquid phases, apart from the charge density wave and superconducting phases for half-integer band fillings. Our study reveals that extended range interactions are necessary to get the correct phase boundary of an one-dimensional interacting bosons system.

cond-mat.supr-con↗

arXiv2006

Excitations of a low-dimensional dimerized spin ladder under a magnetic field

We study the dimerized spin ladder with nearest-neighbor ($J_1$) and next-nearest-neighbor ($J_2$) anti-ferromagnetic interaction under a magnetic field. We predict the existence of different magnetization plateaus for the presence of spin-Peierls interaction on both $J_1$ and $J_2$. Magnetization plateau at $m=0$ for $J_1$ dimerization is spontaneous due to XY interaction, but it is absent for $J_2$ dimerization, only intrinsic umklapp term leads to plateau (spin gap) state for some specific values of XXZ anisotropy ($Δ$) and $J_2$. Here we predict a saturation plateau which is the classical phase of the system. There are some numerical support of our analytical approach already existing in the literature. The transition from commensurate gapped phase to incommensurate Luttinger liquid phase is the Mott-$δ$ type of transition.

cond-mat.str-el↗

arXiv2002

Phase Diagram of the Extended Hubbard Model with Pair Hopping Interaction

A one-dimensional model of interacting electrons with on-site $U$, nearest-neighbor $V$, and pair-hopping interaction $W$ is studied at half-filling using the continuum limit field theory approach. The ground state phase diagram is obtained for a wide range of coupling constants. In addition to the insulating spin- and charge-density wave phases for large $U$ and $V$, respectively, we identify bond-located ordered phases corresponding to an enhanced Peierls instability in the system for $W<0$, $|U-2V|<|2W|$, and to a staggered magnetization located on bonds between sites for $W>0$, $|U-2V|<W$. The general ground state phase diagram including insulating, metallic, and superconducting phases is discussed. A transition to the $η_π$-superconducting phase at $|U-2V| \ll 2t \leq W$ is briefly discussed.

cond-mat↗

arXiv2001

Field theoretical study of a spin-1/2 ladder with unequal chain exchanges

We study the low-energy properties of a Heisenberg spin-1/2 zigzag ladder with different exchange constants on the two chains. Using a nonlinear sigma-model field theory and abelian bosonization, we find that the excitations are gapless, with a finite spin wave velocity, if the values of the chain exchanges are small. If the chain exchanges are large, the system is gapped, and the energy spectra of the kink and antikink excitations are different from each other.

cond-mat.str-el↗