Phase diagram and electronic indication of high-temperature superconductivity at 65 K in single-layer FeSe films

He, Shaolong; He, Junfeng; Zhang, Wenhao; Zhao, Lin; Liu, Defa; Xu, Li; Mou, Daixiang; Ou, Yunbo; Wang, Qingyan; Li, Zhi; Wang, Lili; Peng, Yingying; Liu, Yan; Chen, Chao‐Yu; Yu, Li; Liu, Guodong; Dong, Xianlin; Zhang, Jun; Chen, Chuangtian; Xu, Zuyan; Chen, Xi; Ma, Xu-Cun; Xue, Qi‐Kun; Zhou, Xianju

doi:10.1038/nmat3648

Cited by 781 publications

(790 citation statements)

References 38 publications

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“…Thus, pressure-induced superconductivity in sulfur compounds follows the phonon-centric paradigm at variance with Fe-and Cu-based high-T c superconductors where magnetism is likely to play a prominent role in the pairing mechanism 75 . Mono-and few-layer FeSe is another recent surprise; reports of T c for monolayer specimens on SrTiO 3 substrates range from 65-95 K, far in excess of the T c~8 K of bulk FeSe 79 . The origin of this phenomenon is under debate with both interfacial doping and substrate-modified electron-phonon coupling implicated in the enhancement 80 .…”

Section: Creating Macroscopic Quantum Coherencementioning

confidence: 99%

Towards properties on demand in quantum materials

2017

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Q uantum materials are on the ascent. This term embodies a vast portfolio of compounds and phenomena where ramifications of quantum mechanics are demonstrably real. Quantum materials are in the vanguard of contemporary physics in part because these systems afford an exceptional venue to uncover the many roles of symmetry, topology, dimensionality and strong correlations in macroscopic observables. Here we set out to explore the ways and means of creating new states of matter in quantum materials and manipulating their phases via external stimuli. Practical control of these properties is a precondition for exploiting quantum advantages in new photonic, electronic and energy technologies, a task of significant societal impact 1 . We will primarily focus on the following classes of quantum materials: transition metal oxides, Fe-and Cu-based high-T c superconductors, van der Waals semiconductors, topological insulators and Weyl semimetals, and, finally, graphene.The properties of quantum materials are anomalously sensitive to external stimuli. In these systems, interactions associated with spin, charge, lattice and orbital degrees of freedom are commonly on par with the electronic kinetic energy. A rather fragile balance between coexisting and competing ground states can be readily shifted via external stimuli, leading to a raft of quantum phases and transitions between them 2,3 . Furthermore, certain classes of driven quantum states (Fig. 1a and Box 1) are explicit products of coherent interaction between light and matter 4-6 . Alternatively, the properties of quantum materials can be pre-programmed by directly manipulating the electronic wavefunction and the attendant Berry phase that give rise to the anomalous velocity of electrons in a solid [7][8][9] . These complementary avenues of controls mean that investigations no longer need to be reduced to merely observing (in contrast, for example, to astrophysics). Instead, it is now feasible to attain, in a predictable fashion, 'properties on demand' by steering a quantum material towards a desirable ground, metastable or transient state. The past decade has witnessed an explosion in the field of quantum materials, headlined by the predictions and discoveries of novel Landau-symmetry-broken phases in correlated electron systems, topological phases in systems with strong spin-orbit coupling, and ultra-manipulable materials platforms based on two-dimensional van der Waals crystals. Discovering pathways to experimentally realize quantum phases of matter and exert control over their properties is a central goal of modern condensed-matter physics, which holds promise for a new generation of electronic/photonic devices with currently inaccessible and likely unimaginable functionalities. In this Review, we describe emerging strategies for selectively perturbing microscopic interaction parameters, which can be used to transform materials into a desired quantum state. Particular emphasis will be placed on recent successes to tailor electronic interaction parameters through th...

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Section: Creating Macroscopic Quantum Coherencementioning

confidence: 99%

Towards properties on demand in quantum materials

2017

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“…2 Typical values of T c range between 55-65 K as measured by in situ scanning tunneling microscopy/spectroscopy (STM/STS), 1 angle-resolved photoemission spectroscopy (ARPES), [3][4][5][6] ex situ transport measurements, and Meissner effect studies. [7][8][9] Moreover, a recent in situ transport measurement 10 found a remarkably high T c = 109 K, well above the liquid nitrogen boiling point (77 K).…”

Section: Introductionmentioning

confidence: 99%

“…16 Second, ARPES experiments reveal that the monolayer FeSe on an STO substrate is heavily electron doped such that the Fermi surface consists of only electron pockets at Brillouin zone (BZ) corners. [3][4][5][6] It is generally believed that this electron doping is caused by oxygen vacancies in the STO surface induced by annealing of the substrate before the growth of FeSe. 5 The large electron doping and the resulting Fermi surface with only electron pockets directly challenge the Fermi-surface-nesting driven, purely electronic pairing mechanism.…”

Section: Introductionmentioning

confidence: 99%

Ab initiostudy of cross-interface electron-phonon couplings in FeSe thin films onSrTiO3andBaTiO3

et al. 2016

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We study the electron-phonon coupling strength near the interface of monolayer and bilayer FeSe thin films on SrTiO3, BaTiO3, and oxygen-vacant SrTiO3 substrates, using ab initio methods. The calculated total electron-phonon coupling strength λ = 0.2-0.3 cannot account for the high Tc ∼ 70 K observed in these systems through the conventional phonon-mediated pairing mechanism. In all of these systems, however, we find that the coupling constant of a polar oxygen branch peaks at q = 0 with negligible coupling elsewhere, while the energy of this mode coincides with the offset energy of the replica bands measured recently by angle-resolved photoemission spectroscopy experiments. But the integrated coupling strength for this mode from our current calculations is still too small to produce the observed high Tc, even through the more efficient pairing mechanism provided by the forward scattering. We arrive at the same qualitative conclusion when considering a checkerboard antiferromagnetic configuration in the Fe layer. In light of the experimental observations of the replica band feature and the relatively high Tc of FeSe monolayers on polar substrates, our results point towards a cooperative role for the electron-phonon interaction, where the crossinterface interaction acts in conjunction with a purely electronic interaction. We also discuss a few scenarios where the coupling strength obtained here may be enhanced.

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“…Some theoretical calculations indicate that the iron-based superconductors may be in proximity to a Mott insulator (11,16,17), and attempts have also been made to unify cuprates and ironbased superconductors in theory (18). However, so far no clear experimental evidence of doping (or carrier concentration)-induced insulator-superconductor transition (or crossover) has been reported in the iron-based superconductors.The latest discovery of possible high-temperature superconductivity in the single-layer FeSe films grown on a SrTiO 3 substrate has attracted much attention both experimentally (19)(20)(21)(22)(23)(24)(25)(26)(27) and theoretically (28-32). The reduced dimensionality with enhanced interfacial effect makes this system distinct from its bulk counterpart.…”

mentioning

confidence: 99%

Electronic evidence of an insulator–superconductor crossover in single-layer FeSe/SrTiO ₃ films

Zhang

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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In high-temperature cuprate superconductors, it is now generally agreed that superconductivity is realized by doping an antiferromagnetic Mott (charge transfer) insulator. The doping-induced insulator-to-superconductor transition has been widely observed in cuprates, which provides important information for understanding the superconductivity mechanism. In the iron-based superconductors, however, the parent compound is mostly antiferromagnetic bad metal, raising a debate on whether an appropriate starting point should go with an itinerant picture or a localized picture. No evidence of doping-induced insulator-superconductor transition (or crossover) has been reported in the iron-based compounds so far. Here, we report an electronic evidence of an insulator-superconductor crossover observed in the single-layer FeSe film grown on a SrTiO 3 substrate. By taking angle-resolved photoemission measurements on the electronic structure and energy gap, we have identified a clear evolution of an insulator to a superconductor with increasing carrier concentration. In particular, the insulator-superconductor crossover in FeSe/SrTiO 3 film exhibits similar behaviors to that observed in the cuprate superconductors. Our results suggest that the observed insulator-superconductor crossover may be associated with the twodimensionality that enhances electron localization or correlation. The reduced dimensionality and the interfacial effect provide a new pathway in searching for new phenomena and novel superconductors with a high transition temperature.single-layer FeSe/SrTiO 3 films | insulator-to-superconductor crossover | ARPES T he iron-based superconductors (1-4) represent the second class of high-temperature superconductors after the discovery of the first class of high-temperature cuprate superconductors. It is now generally agreed that the superconductivity in cuprates is realized by doping a Mott (charge transfer) insulator (5). In the iron-based superconductors, however, the parent compounds mostly exhibit a poor metallic behavior with an antiferromagnetic order, thus raising a debate on whether an appropriate starting point should go with an itinerant picture or a localized picture (6-18), particularly whether the picture of doping a Mott insulator is relevant to the iron-based superconductors (1,3,11,16,17). Some theoretical calculations indicate that the iron-based superconductors may be in proximity to a Mott insulator (11,16,17), and attempts have also been made to unify cuprates and ironbased superconductors in theory (18). However, so far no clear experimental evidence of doping (or carrier concentration)-induced insulator-superconductor transition (or crossover) has been reported in the iron-based superconductors.The latest discovery of possible high-temperature superconductivity in the single-layer FeSe films grown on a SrTiO 3 substrate has attracted much attention both experimentally (19)(20)(21)(22)(23)(24)(25)(26)(27) and theoretically (28-32). The reduced dimensionality with enhanced interfacial effect makes ...

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Phase diagram and electronic indication of high-temperature superconductivity at 65 K in single-layer FeSe films

Cited by 781 publications

References 38 publications

Towards properties on demand in quantum materials

Towards properties on demand in quantum materials

Ab initiostudy of cross-interface electron-phonon couplings in FeSe thin films onSrTiO3andBaTiO3

Electronic evidence of an insulator–superconductor crossover in single-layer FeSe/SrTiO ₃ films

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Phase diagram and electronic indication of high-temperature superconductivity at 65 K in single-layer FeSe films

Cited by 781 publications

References 38 publications

Towards properties on demand in quantum materials

Towards properties on demand in quantum materials

Ab initiostudy of cross-interface electron-phonon couplings in FeSe thin films onSrTiO3andBaTiO3

Electronic evidence of an insulator–superconductor crossover in single-layer FeSe/SrTiO 3 films

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Product

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Electronic evidence of an insulator–superconductor crossover in single-layer FeSe/SrTiO ₃ films