arXiv subjects

Igor F. Herbut

Publications and source records attributed to Igor F. Herbut.

At least 127 records · Page 7Linked to original sources

arXiv2002

Antiferromagnetism from phase disordering of a d-wave superconductor

The unbinding of vortex defects in the superconducting condensate with d-wave symmetry at T=0 is shown to lead to the insulator with incommensurate spin-density-wave order. The transition is similar to the spontaneous generation of the "chiral" mass in the three dimensional quantum electrodynamics, at which the global chiral symmetry one can define in the superconducting state is spontaneously broken. Other symmetry related states and possible relations to recent experiments on uderdoped cuprates are briefly discussed.

cond-mat.supr-con↗

arXiv2001

Superconducting zero temperature phase transition in two dimensions and in the magnetic field

We derive the Ginzburg-Landau-Wilson theory for the superconducting phase transition in two dimensions and in the magnetic field. Without disorder the theory describes a fluctuation induced first-order quantum phase transition into the Abrikosov lattice. We propose a phenomenological criterion for determining the transition field and discuss the qualitative effects of disorder. Comparison with recent experiments on MoGe films is discussed.

cond-mat.supr-con↗

arXiv2001

Large-N theory of strongly commensurate dirty-bosons: absence of transition in two dimensions

The spherical limit of strongly commensurate dirty-bosons is studied perturbatively at weak disorder and numerically at strong disorder in two dimensions (2D). We argue that disorder is not perfectly screened by interactions, and consequently that the ground state in the effective Anderson localisation problem always remains localised. As a result there is only a gapped Mott insulator phase in the theory. Comparisons with other studies and the parallel with disordered fermions in 2D are discussed. We conjecture that while for the physical cases N=2 (XY) and N=1 (Ising) the theory should have the ordered phase, it may not for N=3 (Heisenberg).

cond-mat.dis-nn↗

arXiv2001

Quantum critical points with the Coulomb interaction and the dynamical exponent: when and why z=1

A general scenario that leads to Coulomb quantum criticality with the dynamical critical exponent z=1 is proposed. I point out that the long-range Coulomb interaction and quenched disorder have competing effects on z, and that the balance between the two may lead to charged quantum critical points at which z=1 exactly. This is illustrated with the calculation for the Josephson junction array Hamiltonian in dimensions D=3-ε. Precisely in D=3, however, the above simple result breaks down, and z>1. Relation to other theoretical studies is discussed.

cond-mat.supr-con↗

arXiv2000

The effect of a parallel magnetic field on the Boltzmann conductivity and the Hall coefficient of a disordered two dimensional Fermi liquid

Screening of an external random potential by a two dimensional (2D) Fermi liquid may be strongly dependent on the degree of its polarization. This is considered as a possible mechanism for the observed strong magnetoresistance of the 2D electron liquid in the magnetic field parallel to the electron plane. A Hartree-Fock calculation for the weakly disordered Hubbard model which qualitatively describes the experiments on the diagonal and the Hall resisitivity in the finite-temperature metallic state in the high mobility Si inversion layers is presented.

cond-mat.str-el↗

arXiv2000

Zero-temperature d-wave superconducting phase transition

The Ginzburg-Landau-Wilson theory that describes the disordered Fermi liquid - d-wave superconductor phase transition at zero temperature is derived at weak coupling. The theory represents an interacting dissipative system of bosonic Cooper pairs in an effective random potential. I show that there exists a wide crossover regime in the theory controlled by a line of Gaussian fixed points, each of which in two dimensions is characterized by a different universal value of the dc critical conductivity. Relation to experiments on overdoped and underdoped cuprates is discussed.

cond-mat.supr-con↗

arXiv2000

Comment on "Localization and the mobility edge in one-dimensional potentials with correlated disorder"

The equation for the wave-function localization length in terms of the two-point correlation function of a weak random potential in 1D (F. M. Izrailev and A. A. Krokhin, Phys. Rev. Lett. vol. 82, 4062 (1999)) is rederived using the standard weak-localization theory. I propose a modified algorithm for generation of arbitrary correlated random potentials, and show that numerical calculation of the localization length in a specific correlated disorder in 1D is then in accord with the analytic expression, removing the discrepancy noted in the above Letter.

cond-mat.dis-nn↗

arXiv2000

Critical exponents at the superconductor-insulator transition in dirty-boson systems

I obtain the inverse of the correlation length exponent at the superfluid-Bose glass quantum critical point as a series in small parameter $\sqrt{d-1}$, with d being the dimensionality of the system, and compute the first two terms using a novel field-theoretic technique. For d=2 I find $ν_s = 0.81$ and $ν_c = 1.03$, for short-range and Coulomb interactions between bosons, respectively. When combined with the exact values of the dynamical critical exponents $z_s = d$ and $z_c = 1$, these results are in quantitative agreement with the experiments on onset of superfluidity in $^4 He$ in porous glasses, and on superconductor-insulator transition in homogeneous metallic films, in support of the dirty-boson theory fot the latter. Higher-order calculation of the exponents and of the universal conductivity is discussed.

cond-mat.supr-con↗

arXiv2000

Effect of order-parameter fluctuations on the Halperin-Lubensky-Ma first-order transition in superconductors and liquid crystals

We show that order-parameter fluctuations in a good type-I superconductor or a liquid crystal always increase the size of the first-order transition. This behavior is eventually changed when the system crosses over to inverted-XY critical behavior, with the size of the first-order transition vanishing as a power law with a crossover exponent. We find a good agreement between our theory and a recent experiment on the nematic-smectic-A first-order transition in 8CB-10CB mixtures of liquid crystals.

cond-mat.soft↗

arXiv1999

Mean-field theory of strongly disordered superconductors

Qualitative features of the mean-field theory of superconductivity in a strongly disordered systems of fermions with short-range attraction are discussed. In this limit the effective theory is entirely bosonic, and I consider both the artificial infinite-range limit, and the more realistic case of "nearest neighbor" hopping of bosons between localized states. In the infinite range case the mean-field theory is exact, and the superconducting gap is uniform in space. There is a smooth BCS-BEC crossover with decrease in density, at weak enough disorder; at moderate densities, or larger disorder, the mean-field ground state is the BCS-like localized superconductor. In the latter case, the gap is highly non-uniform in space, but surprisingly stays everywhere finite below the mean-field transition temperature.

cond-mat.supr-con↗

arXiv1999

The low-energy theory for the Bose-Hubbard model and the normal ground state of bosons

A bosonic realization of the SU(2) Lie algebra and of its vector representation is constructed, and an effective low-energy description of the Bose-Hubbard model in the form of anisotropic theory of quantum rotors is proposed and discussed. A possibility of a normal zero-temperature bosonic phase with neither crystalline nor superfluid order around the tip of the checkerboard-solid lobe at half-integer fillings is examined.

cond-mat.supr-con↗

arXiv1998

Finite temperature transport at the superconductor-insulator transition in disordered systems

I argue that the incoherent, zero-frequency limit of the universal crossover function in the temperature-dependent conductivity at the superconductor-insulator transition in disordered systems may be understood as an analytic function of dimensionality of system d, with a simple pole at d=1. Combining the exact result for the crossover function in d=1 with the recursion relations in d=1+ε, the leading term in the Laurent series in the small parameter εfor this quantity is computed for the systems of disordered bosons with short-range and Coulomb interactions. The universal, low-temperature, dc critical conductivity for the dirty boson system with Coulomb interaction in d=2 is estimated to be 0.69 (2e)^2 /h, in relatively good agreement with many experiments on thin films. The next order correction is likely to somewhat increase the result, possibly bringing it closer to the self-dual value.

cond-mat.supr-con↗

arXiv1998

Dual theory of the superfluid-Bose glass transition in disordered Bose-Hubbard model in one and two dimensions

I study the zero temperature phase transition between superfluid and insulating ground states of the Bose-Hubbard model in a random chemical potential and at large integer average number of particles per site. Duality transformation maps the pure Bose-Hubbard model onto the sine-Gordon theory in one dimension (1D), and onto the three dimensional Higgs electrodynamics in two dimensions (2D). In 1D the random chemical potential in dual theory couples to the space derivative of the dual field, and appears as a random magnetic field along the imaginary time direction in 2D. I show that the transition from the superfluid state in both 1D and 2D is always controlled by the random critical point. This arises due to a coupling constant in the dual theory with replicas which becomes generated at large distances by the random chemical potential, and represents a relevant perturbation at the pure superfluid-Mott insulator fixed point. At large distances the dual theory in 1D becomes equivalent to the Haldane's macroscopic representation of disordered quantum fluid, where the generated term is identified with random backscattering. In 2D the generated coupling corresponds to the random mass of the complex field which represents vortex loops. I calculate the critical exponents at the superfluid-Bose glass fixed point in 2D to be ν=1.38 and z=1.93, and the universal conductivity at the transition σ_c = 0.26 e_{*}^2 /h, using the one-loop field-theoretic renormalization group in fixed dimension.

cond-mat.supr-con↗

arXiv1998

Critical behavior at superconductor-insulator phase transitions near one dimension

I argue that the system of interacting bosons at zero temperature and in random external potential possesses a simple critical point which describes the proliferation of disorder-induced topological defects in the superfluid ground state, and which is located at weak disorder close to and above one dimension. This makes it possible to address the critical behavior at the superfluid-Bose glass transition in dirty boson systems by expanding around the lower critical dimension d=1. Within the formulated renormalization procedure near d=1 the dynamical critical exponent is obtained exactly and the correlation length exponent is calculated as a Laurent series in the parameter \sqrtε, with ε=d-1: z=d, ν=1/\sqrt{3ε} for the short range, and z=1, ν=\sqrt{2/3ε}, for the long-range Coulomb interaction between bosons. The identified critical point should be stable against the residual perturbations in the effective action for the superfluid, at least in dimensions 1\leq d \leq 2, for both short-range and Coulomb interactions. For the superfluid-Mott insulator transition in the system in a periodic potential and at a commensurate density of bosons I find ν=(1/2\sqrtε)+ 1/4+O(\sqrtε), which yields a result reasonably close to the known XY critical exponent in d=2+1. The critical behavior of the superfluid density, phonon velocity and the compressibility in the system with the short-range interactions is discussed.

cond-mat.supr-con↗

arXiv1997

Dual superfluid-Bose glass critical point in two dimensions and the universal conductivity

We study the continuum version of the dual theory for a system of two-dimensional, zero temperature, disordered bosons, interacting with short range repulsion and at a commensurate density. The dual theory, which describes vortices in the bosonic ground state, and has a form of 3D classical scalar electrodynamics in random, correlated magnetic field, admits a new disordered critical point within RG calculation at fixed dimension. The universal conductivity and the critical exponents at the superfluid-Bose glass critical point are calculated as series in fixed-point values of the dual coupling constants, to the lowest non-trivial order: $σ_c = 0.25 (2e)^2 /h$, $ν=1.38$ and $z=1.93$. The comparison with numerical results and experiments is discussed.

cond-mat.supr-con↗

arXiv1997

Superconductor-insulator quantum critical point in 1+εdimensions

A system of spinless fermions in $d=1+ε$ dimensions, at zero-temperature and in random potential is studied using the perturbative renormalization group to first order in disorder and to second order in interaction. We find a superconductor-to- Anderson insulator quantum fixed point at an infinitesimal value of disorder and calculate the correlation length and the dynamical exponents to the lowest order in $ε$ and in interaction. The scaling of conductivity with temperature and the behavior of characteristic temperature scales on both sides of the transition is determined. The model may have relevance for a p-wave superconductor at low temperatures in strongly disordered media.

cond-mat.supr-con↗

arXiv1997

Reply to comment on "Continuum dual theory of the transition in 3D lattice superconductor"

It is argued that the penetration depth and the correlation length at the critical point of the 3D superconductor diverge with the same critical exponents, as follows from the general scaling arguments and from the independent calculations in both Ginzburg-Landau and its dual theory. The incorrect prediction of Kiometzis, Kleinert and Schakel (KKS) that this is is not so, is the result of the faulty treatment of the dual theory, in which two, instead of one, coupling constants are tuned to reach the critical point. The recent paper by the present author criticized by KKS in cond-mat/9702159 differs on this point from KKS, and consequently finds the expected relation between the divergence of the two lengths in the critical region.

cond-mat.supr-con↗

arXiv1996

Superconducting transition induced by columnar disorder in strong magnetic field

The superconducting transition in presence of strong columnar disorder parallel to the magnetic field is considered. A solvable model appropriate for description of the broad crossover regime towards the true "glassy" critical behavior is constructed, and the behavior of the thermodynamic quantities and of the Edwards-Anderson order-parameter is obtained. The critical exponents for the correlation lengths orthogonal and parallel to the magnetic field are equal and in agreement with the experimental values. The dynamical critical exponent is $z=2$, also in agreement with the measured value. Several perturbations to the solvable model are considered and shown to be irrelevant for the critical behavior. It is argued that there exists an optimal density of defects at which the transition temperature at given magnetic field reaches its maximum.

cond-mat.supr-con↗