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Paata Kakashvili

Publications and source records attributed to Paata Kakashvili.

11 recordsLinked to original sources
arXiv2012

Numerical Simulation of the Nernst Effect in Extreme Type-II Superconductors: A Negative Nernst Signal and its Noise Power Spectra

Recently, different transport coefficients have been measured in High-Tc superconductors to pinpoint the nature of the pseudogap phase. In particular, the thermoelectric coefficients received a considerable attention both theoretically and experimentally. We numerically simulate the Nernst effect in extreme type-II superconductors using the time-dependent Ginzburg-Landau equations. We report the sign reversal of the thermoelectric coefficient, alpha_xy, at temperatures close to the mean-field transition temperature, Tc^{MF}(H), which qualitatively agrees with recent experiments on high-Tc materials. We also discuss the noise power spectrum of alpha_xy, which shows 1/f^beta behavior. Based on this observation, we propose an experiment to distinguish among different regimes of vortex dynamics by measuring the noise correlations of the Nernst signal.

cond-mat.supr-con↗
arXiv2012

Integrability in anyonic quantum spin chains via a composite height model

Recently, properties of collective states of interacting non-abelian anyons have attracted a considerable attention. We study an extension of the `golden chain model', where two- and three-body interactions are competing. Upon fine-tuning the interaction, the model is integrable. This provides an additional integrable point of the model, on top of the integrable point, when the three-body interaction is absent. To solve the model, we construct a new, integrable height model, in the spirit of the restricted solid-on-solid model solved by Andrews, Baxter and Forrester. The heights in our model live on both the sites and links of the square lattice. The model is solved by means of the corner transfer matrix method. We find a connection between local height probabilities and characters of a conformal field theory governing the critical properties at the integrable point. In the antiferromagnetic regime, the criticality is described by the Z_k parafermion conformal field theory, while the su(2)_1 x su(2)_1 x su(2)_(k-2) / su(2)_k coset conformal field theory describes the ferromagnetic regime.

cond-mat.str-el↗
arXiv2010

Dissipative Transport of Trapped Bose-Einstein Condensates through Disorder

After almost half a century since the work of Anderson [Phys. Rev. {\bf 109}, 1492 (1958)], at present there is no well established theoretical framework for understanding the dynamics of interacting particles in the presence of disorder. Here, we address this problem for interacting bosons near $T=0$, a situation that has been realized in trapped atomic experiments with an optical speckle disorder. We develop a theoretical model for understanding the hydrodynamic transport of \emph{finite-size} Bose-Einstein condensates through disorder potentials. The goal has been to set up a simple model that will retain all the richness of the system, yet provide analytic expressions, allowing deeper insight into the physical mechanism. Comparison of our theoretical predictions with the experimental data on large-amplitude dipole oscillations of a condensate in an optical-speckle disorder shows striking agreement. We are able to quantify various dissipative regimes of slow and fast damping. Our calculations provide a clear evidence of reduction in disorder strength due to interactions. The analytic treatment presented here allows us to predict the power law governing the interaction dependance of damping. The corresponding exponents are found to depend sensitively on the dimensionality and are in excellent agreement with experimental observations. Thus, the adeptness of our model, to correctly capture the essential physics of dissipation in such transport experiments, is established.

cond-mat.quant-gas↗
arXiv2008

Paired states in spin-imbalanced atomic Fermi gases in one dimension

A growing expertise to engineer, manipulate and probe different cold-atom analogs of electronic condensed matter systems allows to probe properties of exotic pairing. We study paired states of spin-imbalanced ultracold atomic system of fermions with attractive short-range interactions in one-dimensional traps. Calculations are done using the Bethe Ansatz technique and the trap is incorporated into the solution via a local density approximation. The thermodynamic-Bethe-Ansatz equations are solved numerically and different local density profiles are calculated for zero and finite temperatures. A procedure to identify the homogeneous-system phase diagram using local density profiles in the trap is also proposed. Such scheme would be immediately useful for the experiments.

cond-mat.other↗
arXiv2008

Signatures of Strong Correlations in One-Dimensional Ultra-Cold Atomic Fermi Gases

Recent success in manipulating ultra-cold atomic systems allows to probe different strongly correlated regimes in one-dimension. Regimes such as the (spin-coherent) Luttinger liquid and the spin-incoherent Luttinger liquid can be realized by tuning the inter-atomic interaction strength and trap parameters. We identify the noise correlations of density fluctuations as a robust observable (uniquely suitable in the context of trapped atomic gases) to discriminate between these two regimes. Finally, we address the prospects to realize and probe these phenomena experimentally using optical lattices.

cond-mat.other↗
arXiv2007

Boundary Green's Function for Spin-Incoherent Interacting Electrons in One Dimension

The spin-incoherent regime of one-dimensional electrons has recently been explored using the Bethe ansatz and a bosonized path integral approach, revealing that the spin incoherence dramatically influences the correlations of charge excitations. We here introduce a bosonization scheme for strongly interacting electrons, allowing us to generalize the description to account for the presence of an open boundary. By calculating the single-electron Green's function we find that the charge sector power-law scaling is highly sensitive to the boundary. Our result allows for a detailed description of the crossover between boundary and bulk regimes. We predict that scanning tunneling microscopy on a spin-incoherent system will pick up oscillations in the differential tunneling conductance as a function of the applied voltage $V$ at "intermediate" distances $x$ from a real or a dynamically generated boundary. The wavelength of the oscillations, $πv_c/x$, probes the speed $v_c$ of the charge excitations, and therefore the strength of the electron-electron interaction.

cond-mat.str-el↗
arXiv2007

Time-Loop Formalism for Irreversible Quantum Problems: Steady State Transport in Junctions with Asymmetric Dynamics

Non-unitary quantum mechanics has been used in the past to study irreversibility, dissipation and decay in a variety of physical systems. In this letter, we propose a general scheme to deal with systems governed by non-Hermitian Hamiltonians. We argue that the Schwinger-Keldysh formalism gives a natural description for those problems. To elucidate the method, we study a simple model inspired by mesoscopic physics --an asymmetric junction. The system is governed by a non-Hermitian Hamiltonian which captures essential aspects of irreversibility.

cond-mat.mes-hall↗
arXiv2007

Enhanced Two-Channel Kondo Physics in a Quantum Box Device

We propose a design for a one-dimensional quantum box device where the charge fluctuations are described by an anisotropic two-channel Kondo model. The device consists of a quantum box in the Coulomb blockade regime, weakly coupled to a quantum wire by a single-mode point contact. The electron correlations in the wire produce strong back scattering at the contact, significantly increasing the Kondo temperature as compared to the case of non-interacting electrons. By employing boundary conformal field theory techniques we show that the differential capacitance of the box exhibits manifest two-channel Kondo scaling with temperature and gate voltage, uncontaminated by the one-dimensional electron correlations. We discuss the prospect to experimentally access the Kondo regime with this type of device.

cond-mat.mes-hall↗
arXiv2006

Local Spectral Weight of a Luttinger Liquid: Effects from Edges and Impurities

We calculate the finite-temperature local spectral weight (LSW) of a Luttinger liquid with an "open" (hard wall) boundary. Close to the boundary the LSW exhibits characteristic oscillations indicative of spin-charge separation. The line shape of the LSW is also found to have a Fano-like asymmetry, a feature originating from the interplay between electron-electron interaction and scattering off the boundary. Our results can be used to predict how edges and impurities influence scanning tunneling microscopy (STM) of one-dimensional electron systems at low temperatures and voltage bias. Applications to STM on single-walled carbon nanotubes are discussed.

cond-mat.str-el↗
arXiv2003

Measuring Luttinger Liquid Correlations from Charge Fluctuations in a Nanoscale Structure

We suggest an experiment to study Luttinger liquid behavior in a one-dimensional nanostructure, avoiding the usual complications associated with transport measurements. The proposed setup consists of a quantum box, biased by a gate voltage, and side-coupled to a quantum wire by a point contact. Close to the degeneracy points of the Coulomb blockaded box, and in the presence of a magnetic field sufficiently strong to spin polarize the electrons, the setup can be described as a Luttinger liquid interacting with an effective Kondo impurity. Using exact nonperturbative techniques we predict that the differential capacitance of the box will exhibit distinctive Luttinger liquid scaling with temperature and gate voltage.

cond-mat.str-el↗