Manifestations of impurity-induceds±⇒s++transition: multiband model for dynamical response functions

Efremov, D. V.; Golubov, Alexandre Avraamovitch; Dolgov, O. V.

doi:10.1088/1367-2630/15/1/013002

Cited by 40 publications

(59 citation statements)

References 33 publications

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“…The maximum of the spectra is sf = 144 cm −1 , which determines the natural energy scale [28]. This spectrum gives a rather good description of thermodynamical [58] and optical [59,60] properties in the SC as well as normal states [61].…”

Section: The Eliashberg Approachmentioning

confidence: 81%

Quasiparticle interference in multiband superconductors with strong coupling

et al. 2017

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We develop a theory of the quasiparticle interference (QPI) in multiband superconductors based on the strong-coupling Eliashberg approach within the Born approximation. In the framework of this theory, we study dependencies of the QPI response function in the multiband superconductors with the nodeless s-wave superconductive order parameter. We pay special attention to the difference in the quasiparticle scattering between the bands having the same and opposite signs of the order parameter. We show that at the momentum values close to the momentum transfer between two bands, the energy dependence of the quasiparticle interference response function has three singularities. Two of these correspond to the values of the gap functions and the third one depends on both the gaps and the transfer momentum. We argue that only the singularity near the smallest band gap may be used as a universal tool to distinguish between the s ++ and s ± order parameters. The robustness of the sign of the response function peak near the smaller gap value, irrespective of the change in parameters, in both the symmetry cases is a promising feature that can be harnessed experimentally.

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Section: The Eliashberg Approachmentioning

confidence: 81%

Quasiparticle interference in multiband superconductors with strong coupling

et al. 2017

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“…On the contrary, it has been proposed that 2D systems with a quadratic band crossing point (QBCP) are unstable to electronic correlation because of the finite density of states at the Fermi level leading to the possibility of [21][22][23][24][25][26][27]. For 2D topological states of matter this question is of particular importance, as the global topological nature of the ground state should render such states in principle robust against the local effects of disorder [28].…”

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confidence: 99%

Fate of interaction-driven topological insulators under disorder

et al. 2017

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We analyze the effect of disorder on the weak-coupling instabilities of quadratic band crossing point (QBCP) in two-dimensional Fermi systems, which, in the clean limit, display interactiondriven topological insulating phases. In the framework of a renormalization group procedure, which treats fermionic interactions and disorder on the same footing, we test all possible instabilities and identify the corresponding ordered phases in the presence of disorder for both single-valley and two-valley QBCP systems. We find that disorder generally suppresses the critical temperature at which the interaction-driven topologically non-trivial order sets in. Strong disorder can also cause a topological phase transition into a topologically trivial insulating state.PACS numbers: 73.43. Nq, 71.55.Jv, 11.30.Qc The study of topological phases of matter is one of the most active research areas in contemporary condensed matter physics. The explanation of the quantum Hall effect in terms of the topological properties of the Landau levels [1,2] in the 1980's triggered an intense research effort in the theoretical prediction [3][4][5] and the experimental discovery [6,7] of a plethora of different topologically non-trivial quantum phases. In two-dimensional (2D) insulating systems only two distinct topological non-trivial phases can be realized according to the well-established classification of topological insulators and superconductors [8,9] : (i) the quantum anomalous Hall state (QAH) [3] with a time-reversal symmetry-broken ground state and topologically protected chiral edge states and (ii) the time-reversal invariant quantum spin Hall (QSH) state [4,5], which possesses helical edge states with counterpropagating electrons of opposite spins.In recent years, attention has gradually shifted from non-interacting topological states of matter towards interaction-driven topological phases:many-particle quantum ground-states in which chiral orbital currents or spin-orbit couplings are spontaneously generated by electronic correlations. These states of matter possess both conventional order, characterized by an order parameter and a broken symmetry, and protected edge states associated with a topological quantum number. Interactiondriven QAH and QSH phases were first conceived in the context of 2D honeycomb lattice Dirac fermions [10] assuming sufficiently strong electronic repulsions although more recent analytical and numerical works question the proposal for this particular model [11][12][13][14].On the contrary, it has been proposed that 2D systems with a quadratic band crossing point (QBCP) are unstable to electronic correlation because of the finite density of states at the Fermi level leading to the possibility of The relationship between fixed points QAH and QAH-II is provided in the inset figure of Fig. 2(a).weak-coupling interaction-driven topological insulating phases [15][16][17]. And, indeed, QAH and QSH phases generated by electronic repulsions occur both in the checkerboard lattice model [15,18], and in two-valley QB...

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“…It was suggested some time ago that the scattering on impurities may disentangle sign-changing and signpreserving gaps [5][6][7][8][9] . Usually, nonmagnetic impurity scattering between the bands with different signs of the gaps leads to suppression of the critical temperature T c similar to magnetic impurity scattering in a single-band BCS superconductor 10 .…”

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confidence: 99%

Unexpected impact of magnetic disorder on multiband superconductivity

Korshunov

Efremov

Golubov³

et al. 2014

Phys. Rev. B

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We analyze how the magnetic disorder affects the properties of the two-band s± and s++ models, which are subject of hot discussions regarding iron-based superconductors and other multiband systems like MgB2. We show that there are several cases when the transition temperature Tc is not fully suppressed by magnetic impurities in contrast to the Abrikosov-Gor'kov theory, but a saturation of Tc takes place in the regime of strong disorder. These cases are: (1) the purely interband impurity scattering, (2) the unitary scattering limit. We show that in the former case the s± gap is preserved, while the s++ state transforms into the s± state with increasing magnetic disorder. For the case (2), the gap structure remains intact.

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Manifestations of impurity-induceds_±⇒s₊₊transition: multiband model for dynamical response functions

Cited by 40 publications

References 33 publications

Quasiparticle interference in multiband superconductors with strong coupling

Quasiparticle interference in multiband superconductors with strong coupling

Fate of interaction-driven topological insulators under disorder

Unexpected impact of magnetic disorder on multiband superconductivity

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