Strong and nonmonotonic temperature dependence of Hall coefficient in superconducting<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mtext>K</mml:mtext><mml:mi>x</mml:mi></mml:msub><mml:msub><mml:mtext>Fe</mml:mtext><mml:mrow><mml:mn>2</mml:mn><mml:mo>−</mml:mo><mml:mi>y</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mtext>Se</mml:mtext><mml:mn>2</mml:mn></mml:msub></mml:math>single crystals

Ding, Xiaxin; Pan, Yiming; Yang, Huan; Wen, Hai‐Hu

doi:10.1103/physrevb.89.224515

Cited by 36 publications

(39 citation statements)

References 38 publications

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“…When this differentiation is strong, as in the iron chalcogenides, the normal state of these materials is sufficiently close to an OSMP such that raising temperature has been observed to push them into the OSMP where the d xy orbital completely loses its spectral weight while other orbitals remain itinerant. 15 This has in fact been observed universally for different iron chalcogenides including Fe (Te,Se), KFe 2 Se 2 , and monolayer FeSe film grown on SrTiO 3 [16][17][18][19] ( Fig. 4b) and Nb:BaTiO 3 /KTaO 3 heterostructures.…”

Section: The Normal Statesupporting

confidence: 52%

Role of the orbital degree of freedom in iron-based superconductors

et al. 2017

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Almost a decade has passed since the serendipitous discovery of the iron-based high temperature superconductors (FeSCs) in 2008. The fact that, as in the copper oxide high temperature superconductors, long-range antiferromagnetism in the FeSCs arises in proximity to superconductivity immediately raised the question of the degree of similarity between the two. Despite the great resemblance in their phase diagrams, there exist important differences between the FeSCs and the cuprates that need to be considered in order to paint a full picture of these two families of high temperature superconductors. One of the key differences is the multi-orbital multi-band nature of the FeSCs, which contrasts with the effective single-band nature of the cuprates. Systematic studies of orbital related phenomena in FeSCs have been largely lacking. In this review, we summarize angle-resolved photoemission spectroscopy (ARPES) measurements across various FeSC families that have been reported in literature, focusing on the systematic trends of orbital dependent electron correlations and the role of different Fe 3d orbitals in driving the nematic transition, the spin-density-wave transition, and superconductivity.

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Section: The Normal Statesupporting

confidence: 52%

Role of the orbital degree of freedom in iron-based superconductors

et al. 2017

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“…(13), which shows that the slave-spin operatorz α for orbital α experiences an effective field of h α = β Q f αβ z β , where Q f αβ is defined in Eq. (14). Similar reasoning as in the previous paragraph gives rise to…”

Section: Landau Free-energy Functional and The Origin Of The Orbsupporting

confidence: 48%

“…The OSMP phase arises in multiorbital Hubbard models of the FeSCs, which contain both Hubbard interactions and Hund's coupling 11,12 . Evidence for the OSMP has also come from a variety of other measurements [13][14][15][16] . A complementary approach to the electron correlations of the FeSCs describes the localization-delocalization phenomena in the form of an orbital differentiation and a coherence-incoherence crossover 17,18 , though OSMP is not explicitly invoked.…”

Section: Introductionmentioning

confidence: 99%

Orbital-selective Mott phase in multiorbital models for iron pnictides and chalcogenides

2017

Phys. Rev. B

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There is increasing recognition that the multiorbital nature of the 3d electrons is important to the proper description of the electronic states in the normal state of the iron-based superconductors. Earlier studies of the pertinent multiorbital Hubbard models identified an orbital-selective Mott phase, which anchors the orbitalselective behavior seen in the overall phase diagram. An important characteristics of the models is that the orbitals are kinetically coupled -i.e. hybridized -to each other, which makes the orbital-selective Mott phase especially nontrivial. A U (1) slave-spin method was used to analyze the model with nonzero orbital-level splittings. Here we develop a Landau free-energy functional to shed further light on this issue. We put the microscopic analysis from the U (1) slave-spin approach in this perspective, and show that the intersite spin correlations are crucial to the renormalization of the bare hybridization amplitude towards zero and the concomitant realization of the orbital-selective Mott transition. Based on this insight, we discuss additional ways to study the orbital-selective Mott physics from a dynamical competition between the interorbital hybridization and collective spin correlations. Our results demonstrate the robustness of the orbital-selective Mott phase in the multiorbital models appropriate for the iron-based superconductors.

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“…These materials include the alkaline iron selenides, the Te-doped "11" iron selenides FeSe, and the monolayer FeSe on the SrTiO 3 substrate. [22][23][24][25][26] The effective quasiparticle mass normalized by its non-interacting counterpart, m * /m band is on the order of 3-4 for the 3d xz,yz orbitals, but is as large as 20 for the 3d xy orbital. 22,23,28 Such orbital selectivity has also been the subject of extensive recent theoretical studies.…”

Section: Resultsmentioning

confidence: 99%

“…Thus, there is reason to expect that correlation effects will be different for different orbitals. In fact, there is evidence for orbitally selective Mott behavior in the iron selenides [22][23][24][25][26] and, thus, orbital selectivity is to be expected for pairing as well.…”

Section: Introductionmentioning

confidence: 99%

Orbital-selective pairing and superconductivity in iron selenides

Nica

2017

npj Quant Mater

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An important challenge in condensed matter physics is understanding iron-based superconductors. Among these systems, the iron selenides hold the record for highest superconducting transition temperature and pose especially striking puzzles regarding the nature of superconductivity. The pairing state of the alkaline iron selenides appears to be of d-wave type based on the observation of a resonance mode in neutron scattering, while it seems to be of s-wave type from the nodeless gaps observed everywhere on the Fermi surface. Here we propose an orbital-selective pairing state, dubbed sτ 3 , as a natural explanation of these disparate properties. The pairing function, containing a matrix τ 3 in the basis of 3d-electron orbitals, does not commute with the kinetic part of the Hamiltonian. This dictates the existence of both intraband and interband pairing terms in the band basis. A spin resonance arises from a d-wave-type sign change in the intraband pairing component, whereas the quasiparticle excitation is fully gapped on the FS due to an s-wave-like form factor associated with the addition in quadrature of the intraband and interband pairing terms. We demonstrate that this pairing state is energetically favored when the electron correlation effects are orbitally selective. More generally, our results illustrate how the multiband nature of correlated electrons affords unusual types of superconducting states, thereby shedding new light not only on the iron-based materials but also on a broad range of other unconventional superconductors such as heavy fermion and organic systems.

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Strong and nonmonotonic temperature dependence of Hall coefficient in superconductingKxFe2−ySe2single crystals

Cited by 36 publications

References 38 publications

Role of the orbital degree of freedom in iron-based superconductors

Role of the orbital degree of freedom in iron-based superconductors

Orbital-selective Mott phase in multiorbital models for iron pnictides and chalcogenides

Orbital-selective pairing and superconductivity in iron selenides

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