Effect of inhomogeneity on<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>s</mml:mi></mml:math>-wave superconductivity in the attractive Hubbard model

Aryanpour, Karan; Dagotto, Elbio; Mayr, Matthias; Paiva, Thereza; Pickett, Warren E.; Scalettar, Richard

doi:10.1103/physrevb.73.104518

Cited by 38 publications

(40 citation statements)

References 30 publications

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“…Unlike BCS, this Monte Carlo mean field (MCMF) approach allows identification of the weak and strong coupling regimes via the phase correlation function. In an earlier work 49 this Monte Carlo technique was employed as an independent examination for the validity of our results and the agreement between the two techniques was clearly confirmed.…”

Section: Model and Methodologysupporting

confidence: 72%

“…This model is the attractive Hubbard model, which has been applied previously to address some aspects of the impact of inhomogeneity. Recently old suggestions based on "negative U" superconductivity have been revived, 49,51 which may provide additional applications for the results we present in this paper. Tl-doped PbTe achieves a critical temperature up to 1.5 K, and more extensive heat capacity and transport data 52,53 have led to an analysis in terms of a "charge Kondo effect" that could be linked to the observed superconductivity.…”

Section: 20mentioning

confidence: 79%

“…[48] and also in Ref. [49]. Recently, the XY model Hamiltonian with certain types of inhomogeneous patterns for the coupling constant between spins sitting on two nearest neighboring sites has also been shown to enhance T c by Loh et al in Ref.…”

Section: 20mentioning

confidence: 86%

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s-wave superconductivity phase diagram in the inhomogeneous two-dimensional attractive Hubbard model

et al. 2007

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We study s-wave superconductivity in the two-dimensional square lattice attractive Hubbard Hamiltonian for various inhomogeneous patterns of interacting sites. Using the Bogoliubov-de Gennes (BdG) mean field approximation, we obtain the phase diagram for inhomogeneous patterns in which the on-site attractive interaction Ui between the electrons takes on two values, Ui = 0 and −U/(1 − f ) (with f the concentration of non-interacting sites) as a function of average electron occupation per site n, and study the evolution of the phase diagram as f varies. In certain regions of the phase diagram, inhomogeneity results in a larger zero temperature average pairing amplitude (order parameter) and also a higher superconducting (SC) critical temperature Tc, relative to a uniform system with the same mean interaction strength (Ui = −U on all sites). These effects are observed for stripes, checkerboard, and even random patterns of the attractive centers, suggesting that the pattern of inhomogeneity is unimportant. The phase diagrams also include regions where superconductivity is obliterated due to the formation of various charge ordered phases. The enhancement of Tc due to inhomogeneity is robust as long as the electron doping per site n is less than twice the fraction of interacting sites [2(1 − f )] regardless of the pattern. We also show that for certain inhomogeneous patterns, when n = 2(1 − f ), increasing temperature can work against the stability of existing charge ordered phases for large f and as a result, enhance Tc. PACS numbers:I. MOTIVATION Fascination with inhomogeneous superconducting (SC) phases extends back several decades, with many conferences and monographs having been devoted to the subject.1,2,3 For conventional superconductors, the inhomogeneities were extrinsic, arising from a granular nature of samples or due to the deliberate synthesis of disordered built materials or films. The high temperature superconductors (HTS) introduced new aspects into this area of study. First, inhomogeneous states (normal and SC) seem to be intrinsic to HTS, at least in the underdoped regime, similar to quenched disorder in the metalinsulator transition in two dimensions.4,5 Secondly, the inhomogeneity occurs on a smaller length scale of just a few lattice constants as evidenced by scanning tunneling spectroscopy (STS) at the nanoscale. 6,7,8,9 In addition, the strong electronic correlation in HTS cuprates plays a major role in the elucidation of the inhomogeneous SC state; indeed the inhomogeneity is widely believed to arise from the strong intra-atomic interactions that tend to frustrate bandlike conduction, to induce local magnetic moments, and to drive charge and spin order on a few lattice constant scale. The study of the doped Mott insulating phase has been one of the most active areas of theoretical study of HTS, one that has proven to be unexpectedly complex and rich and which is still under intense exploration and debate. Surprisingly, holes doped into the high temperature superconductors tend to arrange themse...

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Section: Model and Methodologysupporting

confidence: 72%

Section: 20mentioning

confidence: 79%

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s-wave superconductivity phase diagram in the inhomogeneous two-dimensional attractive Hubbard model

et al. 2007

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“…55,56 It was shown that an exponentially decaying subgap density of states appears due to mesoscopic fluctuations which lie beyond the mean-field picture. Finally, inhomogeneous couplings in the attractive Hubbard model 57,58 and lattice XY model 59 were also analyzed, with relevance to high-T c materials.…”

Section: Introductionmentioning

confidence: 99%

Effect of inhomogeneous coupling on BCS superconductors

2008

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We investigate the influence of inhomogeneity in the pairing coupling constant U͑r ជ͒ on dirty BCS superconductors, focusing on T c , the order parameter ⌬͑r ជ͒, and the energy gap E g ͑r ជ͒. Within mean-field theory, we find that when the length scale of the inhomogeneity is comparable to or larger than the coherence length, the ratio 2E g / T c is significantly reduced from that of a homogeneous superconductor, while in the opposite limit, this ratio stays unmodified. In two dimensions, when strong phase fluctuations are included, the KosterlitzThouless temperature T KT is also studied. We find that when the inhomogeneity length scale is much larger than the coherence length, 2E g / T KT can be larger than the usual BCS value. We use our results to qualitatively explain recent experimental observation of a surprisingly low value of 2E g / T c in thin films.

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“…This has been illustrated in several recent works. [3][4][5]9,10,16,[19][20][21] The main aim of this paper is to present a real-space approach to study the effect of disorder on superconductivity going beyond standard mean-field techniques for the purpose of configuration averaging. This will be based on the augmented space recursion ͑ASR͒ formalism introduced by one of us.…”

Section: Introductionmentioning

confidence: 99%

Augmented space recursion study of the effect of disorder on superconductivity

et al. 2009

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We present a real-space approach to study the effect of disorder on superconductivity. The method is based on augmented space formalism that goes beyond mean-field approximations for configuration averaging and effectively deals with the influence of configuration fluctuations of the neighborhood of an atom. In the regime of validity of Anderson's theorem our results for s-and d-wave dirty superconductors have excellent agreement with existing results. The formalism is extended and tested for random negative U Hubbard model. Having verified the reliability of our method we use it to study environment-dependent inhomogeneous randomness in disordered superconducting systems.

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Effect of inhomogeneity ons-wave superconductivity in the attractive Hubbard model

Cited by 38 publications

References 30 publications

s-wave superconductivity phase diagram in the inhomogeneous two-dimensional attractive Hubbard model

s-wave superconductivity phase diagram in the inhomogeneous two-dimensional attractive Hubbard model

Effect of inhomogeneous coupling on BCS superconductors

Augmented space recursion study of the effect of disorder on superconductivity

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