London penetration depth in the tight binding approximation: orthorhombic distortion and oxygen isotope effects in cuprates

Erëmin, M. V.; Larionov, I. A.; Lyubin, I. E.

doi:10.1088/0953-8984/22/18/185704

Cited by 10 publications

(11 citation statements)

References 49 publications

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“…Therefore we approximate the superconducting gap in the form ∆ k = ∆ 0 (cos k x a − cos k y a) /2. The magnitude of ∆ 0 ≈ 30meV is obtained from the temperature dependencies of the nuclear relaxation rate [24] and superfluid density [25] for Y Ba 2 Cu 3 O 7 . The energy dispersion is given by (5) and we employ the following minimal set of effective hoping parameters (in meV): t The calculated imaginary part of susceptibility in the normal phase for T = 100K is shown in Fig.…”

Section: Numerical Results and Comparison To Experimental Datamentioning

confidence: 99%

Dual features of magnetic susceptibility in superconducting cuprates: a comparison to inelastic neutron scattering

2012

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Section: Numerical Results and Comparison To Experimental Datamentioning

confidence: 99%

Dual features of magnetic susceptibility in superconducting cuprates: a comparison to inelastic neutron scattering

2012

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“…Indeed, the penetration depth λ should display an anisotropy that is directly related to the superconducting order parameter. To make predictions for our proposed gap state, we calculate the penetration depth from the current-current correlator as follows 39,40 : Assuming that contributions from individual bands ν at the Fermi level simply sum up in the correlator 41 , we obtain for the current direction i The corresponding result from a single band calculation is given by…”

Section: Penetration Depth Anisotropymentioning

confidence: 99%

“…(6) for ≈ 10 6 k points as in the calculation of the susceptibility in the superconducting state, we set T c = 9 K and use a mean-field-like T dependence of the superconducting order parameter, setting ∆ k = g(k)∆ 0 tanh(1.76 · T c /T − 1). 40 In the inset of Fig. 8 we show the result for the two eigenvalues of the superfluid density tensor, ∝ 1/λ(T ) 2 , corresponding to current in the x and y directions, respectively.…”

Section: Penetration Depth Anisotropymentioning

confidence: 99%

Spin excitations in a model of FeSe with orbital ordering

et al. 2015

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We present a theoretical study of the dynamical spin susceptibility for the intriguing Fe-based superconductor FeSe, based on a tight-binding model developed to account for the temperaturedependent band structure in this system. The model allows for orbital ordering in the dxz/dyz channel below the structural transition and presents a strongly C4 symmetry broken Fermi surface at low temperatures which accounts for the nematic properties of this material. The calculated spin excitations are peaked at wave vector (π, 0) in the 1-Fe Brillouin zone, with a broad maximum at energies of order a few meV. In this range, the occurrence of superconductivity sharpens this peak in energy, creating a (π, 0) "neutron resonance" as seen in recent experiments. With the exception of the quite low energy scale of these fluctuations, these results are roughly similar to standard behavior in Fe pnictide systems. At higher energies, however, intensity increases and shifts to wave vectors along the (π, 0) -(π, π) line. We compare with existing inelastic neutron experiments and NMR data, and give predictions for further studies.

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“…When calculating the London depth λ the Fourier transform of the vector potential A q is to be considered in the long wavelength limit: q = 0 [40,41]. Following [42], for simplicity, we direct the vector potential along the x axis, but, in contrast to [42], we do not expand factors (10) in powers of A x q=0 . Retaining factor (10) in an exponential form, we transform operators in the Hamiltonian of SFM from the Wannier to the quasi-momentum representation.…”

Section: The London Penetration Depthmentioning

confidence: 99%

Effect of Coulomb repulsion on the London penetration depth in cuprate superconductors

Komarov¹,

Dzebisashvili²

2020

Phys. Scr.

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We study the effect of Coulomb repulsion between oxygen holes on the London penetration depth λ based on the concept of spin-polaron nature of Fermi quasiparticles in cuprates superconductors. It is shown that for the generally accepted values of the parameters of the spin-fermion model, taking into account the Coulomb interaction, both the one-site Hubbard U p and interaction between the holes on nextnearest-neighbor oxygen ions V 2 , allows one to achieve a much better agreement of the calculated temperature dependencies of the value λ −2 with the experimental data in La 2−x Sr x CuO 4 with optimal doping. Effect of Coulomb repulsion on the London penetration depth in cuprate superconductors2 IntroductionThe existence of strong electron correlations (SEC), due to the significant Coulomb interaction of holes in d x 2 −y 2 -orbitals of copper ions, essentially complicates the study of low-temperature properties of cuprate high-temperature superconductors (HTSC). On the other hand, it is the large value of this interaction that allows to integrate out the high-energy states in the, most realistic for cuprates, three-band p−d model or the Emery model [1,2,3,4,5] and to obtain a more simple spin-fermion model (SFM) [6,7,8,9,10]. An important difference of the last model from the other effective lowenergy models of cuprates, such as the Hubbard model (for example, [11,12]) or the t−J model ([13]), is that the SFM clearly takes into account the spatial separation of hole states on the copper ion and two oxygen ions in one unit cell of CuO 2 -planes.Within SFM, the concept of a spin polaron was developed [14,15,16], which made it possible to achieve significant progress in describing the properties of cuprates both in the normal [16,17,18,19,20,21], and superconducting [22,23,24] phases. In particular, in Refs. [22,23,24] it was shown that the Cooper instability develops in an ensemble of spin polarons, and the exchange interaction between the spins localized on copper ions causes an effective attraction between spin-polaron quasiparticles.Recently, in [25], the spin polaron concept was used to describe the dependence of the London penetration depth λ on the temperature T in hole-doped cuprate HTSCs. An important result of these studies was the detection of the so-called inflection point in the calculated curves of λ −2 (T ), which was experimentally observed, for example, in La 1.83 Sr 0.17 CuO 4 [26, 27], YBa 2 Cu 3 O 7−δ [28, 29] and Bi 2.15 Sr 1.85 CaCu 2 O 8+δ [30].Unfortunately in [25] the theoretical curves λ −2 (T ) exceeded the experimental ones for the La 2−x Sr x CuO 4 [31] by 30%-40%, both regarding the value of λ −2 0 (i.e. λ −2 at T = 0) and the value of T c which is the temperature at which λ diverges. It is important to note that parameters of the SFM were not adjusted, but were chosen equal to those used earlier [18,19,21,22,23,24]. To obtain a satisfactory agreement of the λ −2 (T ) curves with the experimental data, it was necessary to reduce by almost two times both the parameter of the spin-fermio...

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London penetration depth in the tight binding approximation: orthorhombic distortion and oxygen isotope effects in cuprates

Cited by 10 publications

References 49 publications

Dual features of magnetic susceptibility in superconducting cuprates: a comparison to inelastic neutron scattering

Dual features of magnetic susceptibility in superconducting cuprates: a comparison to inelastic neutron scattering

Spin excitations in a model of FeSe with orbital ordering

Effect of Coulomb repulsion on the London penetration depth in cuprate superconductors

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