arXiv subjects

Ovidiu I. Patu

Publications and source records attributed to Ovidiu I. Patu.

32 records · Page 2Linked to original sources

arXiv2015

Thermodynamics, density profiles and correlation functions of the inhomogeneous one-dimensional spinor Bose gas

We investigate the finite temperature properties of the one-dimensional two-component Bose gas (2CBG) with repulsive contact interaction in a harmonic trap. Making use of a new lattice embedding for the 2CBG and the quantum transfer matrix we derive a system of two nonlinear integral equations characterizing the thermodynamics of the uniform system for all values of the relevant parameters: temperature, strength of the interaction, chemical potential and magnetic field. This system allows for an easy numerical implementation in stark contrast with the infinite number of equations obtained by employing the thermodynamic Bethe ansatz. We use this exact solution coupled with the local density approximation to compute the density profiles and local density correlation function of the inhomogeneous gas for a wide range of coupling strengths and temperatures. Our results show that the polarization in the center of the trap influences heavily the local correlator especially in the experimentally accessible Tonks-Girardeau regime.

cond-mat.quant-gas↗

arXiv2015

Correlation functions and momentum distribution of one-dimensional hard-core anyons in optical lattices

We address the problem of calculating the correlation functions in a system of one-dimensional hard-core anyons that can be experimentally realized in optical lattices. Using the summation of form factors we have obtained Fredholm determinant representations for the time-, space-, and temperature-dependent Green's functions which are particularly suited to numerical investigations. In the static case we have also derived the large distance asymptotic behavior of the correlators and computed the momentum distribution function at zero and finite temperature. We present extensive numerical results highlighting the characteristic features of one-dimensional systems with fractional statistics.

cond-mat.quant-gas↗

arXiv2014

Temperature-driven crossover in the Lieb-Liniger model

The large-distance behavior of the density-density correlation function in the Lieb-Liniger model at finite temperature is investigated by means of the recently derived nonlinear integral equations characterizing the correlation lengths. We present extensive numerical results covering all the physical regimes fromweak to strong interaction and all temperatures. We find that the leading term of the asymptotic expansion becomes oscillatory at a critical temperature which decreases with the strength of the interaction. As we approach the Tonks-Girardeau limit the asymptotic behavior becomes more complex with a double crossover of the largest and next-largest correlation lengths. The crossovers exist only for intermediate couplings and vanish for $γ=0$ and $γ=\infty$.

cond-mat.quant-gas↗

arXiv2013

Correlation lengths of the repulsive one-dimensional Bose gas

We investigate the large-distance asymptotic behavior of the static density-density and field-field correlation functions in the one-dimensional Bose gas at finite temperature. The asymptotic expansions of the Bose gas correlators are obtained performing a specific continuum limit in the similar low-temperature expansions of the longitudinal and transversal correlation functions of the XXZ spin chain. In the lattice system the correlation lengths are computed as ratios of the largest and next-largest eigenvalues of the XXZ spin chain quantum transfer matrix. In both cases, lattice and continuum, the correlation lengths are expressed in terms of solutions of Yang-Yang type [C.N. Yang and C.P. Yang, J.Math.Phys. 10, 1151 (1969)] non-linear integral equations which are easily implementable numerically.

math-ph↗

arXiv2011

Efficient Thermodynamic Description of Multi-Component One-Dimensional Bose Gases

We present a new method of obtaining nonlinear integral equations characterizing the thermodynamics of one-dimensional multi-component gases interacting via a delta-function potential. In the case of the repulsive two-component Bose gas we obtain a simple system of two NLIE allowing for an efficient numerical implementation in contrast with the infinite number of coupled equations obtained by employing the Thermodynamic Bethe Ansatz. Our technique makes use of the Quantum Transfer Matrix and the fact that in a certain continuum limit multi-component gases can be obtained from appropriate anisotropic spin chains.

cond-mat.stat-mech↗

arXiv2009

One-Dimensional Impenetrable Anyons in Thermal Equilibrium. IV. Large Time and Distance Asymptotic Behavior of the Correlation Functions

This work presents the derivation of the large time and distance asymptotic behavior of the field-field correlation functions of impenetrable one-dimensional anyons at finite temperature. In the appropriate limits of the statistics parameter, we recover the well-known results for impenetrable bosons and free fermions. In the low-temperature (usually expected to be the "conformal") limit, and for all values of the statistics parameter away from the bosonic point, the leading term in the correlator does not agree with the prediction of the conformal field theory, and is determined by the singularity of the density of the single-particle states at the bottom of the single-particle energy spectrum.

cond-mat.stat-mech↗

arXiv2009

Non-conformal asymptotic behavior of the time-dependent field-field correlators of 1D anyons

The exact large time and distance behavior of the field-field correlators has been computed for one-dimensional impenetrable anyons at finite temperatures. The result reproduces known asymptotics for impenetrable bosons and free fermions in the appropriate limits of the statistics parameter. The obtained asymptotic behavior of the correlators is dominated by the singularity in the spectral density of the quasiparticle states at the bottom of the band, and differs from the predictions of the conformal field theory. One can argue, however, that the anyonic response to the low-energy probes is still determined by the conformal terms in the asymptotic expansion.

cond-mat.stat-mech↗

arXiv2009

One-Dimensional Impenetrable Anyons in Thermal Equilibrium. III. Large distance asymptotics of the space correlations

Using the determinant representation for the field-field correlation functions of impenetrable anyons at finite temperature obtained in a previous paper, we derive a system of nonlinear partial differential equations completely characterizing the correlators. The system is the same as the one for impenetrable bosons but with different initial conditions. The large-distance asymptotic behavior of the correlation functions is obtained from the analysis of the Riemann-Hilbert problem associated with the system of differential equations. We calculate both the exponential and pre-exponential factors in the asymptotics of the field-field correlators. The asymptotics derived in this way agree with those of the free fermions and impenetrable bosons in the appropriate limits, $κ\to 1$ and $κ\to 0$, of the statistics parameter $κ$, and coincide with the predictions of the conformal field theory at low temperatures.

cond-mat.stat-mech↗

arXiv2008

Large-Distance Asymptotic Behavior of the Correlation Functions of 1D Impenetrable Anyons at Finite Temperatures

The large-distance asymptotic behavior of the field-field correlators has been computed for one-dimensional impenetrable anyons at finite temperatures. The asymptotic behavior agrees with the predictions of conformal field theory at low temperatures and reproduces the known results for impenetrable bosons and free fermions in appropriate limits. We have also obtained an integrable system of partial nonlinear differential equations which completely characterizes the 2-point correlation functions. The system is the same as for bosons but with different initial conditions.

cond-mat.stat-mech↗

arXiv2008

One-Dimensional Impenetrable Anyons in Thermal Equilibrium. II. Determinant Representation for the Dynamic Correlation Functions

We have obtained a determinant representation for the time- and temperature-dependent field-field correlation function of the impenetrable Lieb-Liniger gas of anyons through direct summation of the form factors. In the static case, the obtained results are shown to be equivalent to those that follow from the anyonic generalization of Lenard's formula.

cond-mat.stat-mech↗

arXiv2008

One-Dimensional Impenetrable Anyons in Thermal Equilibrium. I. Anyonic Generalization of Lenard's Formula

We have obtained an expansion of the reduced density matrices (or, equivalently, correlation functions of the fields) of impenetrable one-dimensional anyons in terms of the reduced density matrices of fermions using the mapping between anyon and fermion wavefunctions. This is the generalization to anyonic statistics of the result obtained by A. Lenard for bosons. In the case of impenetrable but otherwise free anyons with statistical parameter $κ$, the anyonic reduced density matrices in the grand canonical ensemble is expressed as Fredholm minors of the integral operator ($1-γ\hat θ_T$) with complex statistics-dependent coefficient $γ=(1+e^{\pm iπκ})/ π$. For $κ=0$ we recover the bosonic case of Lenard $γ=2/π$. Due to nonconservation of parity, the anyonic field correlators $\la \fad(x')\fa(x)\ra$ are different depending on the sign of $x'-x$.

cond-mat.stat-mech↗

arXiv2008

Correlation Functions of One-Dimensional Lieb-Liniger Anyons

We have investigated the properties of a model of 1D anyons interacting through a $δ$-function repulsive potential. The structure of the quasi-periodic boundary conditions for the anyonic field operators and the many-anyon wavefunctions is clarified. The spectrum of the low-lying excitations including the particle-hole excitations is calculated for periodic and twisted boundary conditions. Using the ideas of the conformal field theory we obtain the large-distance asymptotics of the density and field correlation function at the critical temperature T=0 and at small finite temperatures. Our expression for the field correlation function extends the results in the literature obtained for harmonic quantum anyonic fluids.

cond-mat.stat-mech↗

arXiv2007

Free Energy of the Eight Vertex Model with an Odd Number of Lattice Sites

We calculate the bulk contribution for the doubly degenerated largest eigenvalue of the transfer matrix of the eight vertex model with an odd number of lattice sites N in the disordered regime using the generic equation for roots proposed by Fabricius and McCoy. We show as expected that in the thermodynamic limit the result coincides with the one in the N even case.

cond-mat.stat-mech↗

arXiv2007

XXX Spin Chain: from Bethe Solution to Open Problems

We present some open problems in the field of exactly solvable models. Two of the problems are related to the correlation functions of the XXX spin chain and the XXZ spin chain, one to the entropy of subsystems and one to the six vertex model with domain wall boundary conditions.

cond-mat.stat-mech↗