Orbital Origin of Extremely Anisotropic Superconducting Gap in Nematic Phase of FeSe Superconductor

Liu, Defa; Liu, Cong; Huang, Jianwei; Lei, Bin; Wang, Le; Wu, Xianxin; Shen, Bing; Gao, Qiang; Zhang, Yuxiao; Liu, Xu; Hu, Yong; Xu, Yu; Liang, Aiji; Liu, Jing; Ai, Ping; Zhao, Lin; He, Songtao; Yu, Li; Liu, Guodong; Mao, Yixin; Dong, Xianlin; Jia, Xiaofei; Zhang, Fengfeng; Zhang, Shenjin; Yang, Feng; Wang, Zhimin; Peng, Qinjun; Shi, Youguo; Hu, Jiangping; Xiang, Tao; Chen, Xianhui; Xu, Zuyan; Chen, Chuangtian; Zhou, Xingjiang

doi:10.1103/physrevx.8.031033

Cited by 82 publications

(107 citation statements)

References 57 publications

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“…Similar to the stripe-type AFM order, the nematic order also breaks the lattice four-fold (C 4 ) rotational symmetry of a high-temperature phase, as evidenced by a tetragonal-to-orthorhombic structural phase transition at T s [7][8][9][10][11]. On the other hand, the nematic order is directly linked to the superconducting state because nematic instability is a characteristic feature of the normal state upon which at lower temperatures the superconductivity emerges [1,8,12,13], and thus nematicity is deemed a precursor of superconductivity in unconventional superconductors including the cuprates. It is generally believed that the nematic order is electronic and the structural phase transition is the consequence of the nematic order, since the lattice distortion is much smaller than the observed anisotropy of the in-plane resistivity in the nematic phase [9,14].…”

Section: Introductionmentioning

confidence: 95%

Observation of orbital ordering and origin of the nematic order in FeSe

Cao

Dong

et al. 2019

New J. Phys.

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In iron-based superconductors the interactions driving the nematic order that breaks the lattice fourfold rotational symmetry in the iron plane may also facilitate the Cooper pairing, but experimental determination of these interactions is challenging because the temperatures of the nematic order and the order of other electronic phases appear to match each other or to be close to each other. Here we performed field-dependent 77 Se-nuclear magnetic resonance (NMR) measurements on single crystals of iron-based superconductor FeSe, with magnetic field B 0 up to 16 T. The 77 Se-NMR spectra and Knight shift split when the direction of B 0 is away from the direction perpendicular to the iron planes (i.e. B 0 Pc) upon cooling in temperature, with a significant change in the distribution and magnitude of the internal magnetic field at the 77 Se nucleus, but these do not happen when B 0 is perpendicular to the iron planes, thus demonstrating that there is an orbital ordering. Moreover, stripe-type antiferromagnetism is absent, while giant antiferromagnetic spin fluctuations measured by the NMR spin-lattice relaxation gradually developed starting at ∼40 K, which is far below the nematic order temperature T nem =89 K. These results provide direct evidence of orbital-driven nematic order in FeSe.

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Section: Introductionmentioning

confidence: 95%

Observation of orbital ordering and origin of the nematic order in FeSe

Cao

Dong

et al. 2019

New J. Phys.

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“…In particular, two aspects are actively debated in literature in the case of FeSe. i) The nematic energy scale of the orbital anisotropy between d xz and d yz is interpreted as either much larger than (∼50 meV) [36][37][38][39][40][41][42][43][44][45], or on par with the lattice distortion and superconducting energy scales (≤10 meV) [46][47][48]. This discrepancy has caused a revisit of theoretical understanding of the electronic nematic order in FeSe.…”

Section: Introductionmentioning

confidence: 99%

Nematic Energy Scale and the Missing Electron Pocket in FeSe

et al. 2019

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Superconductivity emerges in proximity to a nematic phase in most iron-based superconductors. It is therefore important to understand the impact of nematicity on the electronic structure. Orbital assignment and tracking across the nematic phase transition proved to be challenging due to the multiband nature of iron-based superconductors and twinning effects. Here we report a detailed study of the electronic structure of fully detwnned FeSe across the nematic phase transition using angle-resolved photoemission spectroscopy. We clearly observe a nematicity-driven bandreconstruction involving dxz, dyz and dxy orbitals. The nematic energy scale between dxz and dyz bands reach a maximum of 50meV at the Brillouin zone corner. We are also able to track the dxz electron pocket across the nematic transition and explain its absence in the nematic state. Our comprehensive data of the electronic structure provide an accurate basis for theoretical models of the superconducting pairing in FeSe.

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“…The multiferroicity in GeV4S8 is thought to originate from an orbital ordering that reorganizes the charge within the transition metal clusters [5]. Furthermore, electron orbitals are considered to be the origin of the extremely anisotropic superconducting gap in the nematic phase of FeSe superconductors [6]. Although less explored than spins, orbitals are attracting increasing attention in quantum information science and applications [7].…”

Section: Introductionmentioning

confidence: 99%

Orbital-flop Induced Magnetoresistance Anisotropy in Rare Earth Monopnictide CeSb

Bao

et al. 2019

Nat Commun

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The charge and spin of the electrons in solids have been extensively exploited in electronic devices and in the development of spintronics. Another attribute of electrons—their orbital nature—is attracting growing interest for understanding exotic phenomena and in creating the next-generation of quantum devices such as orbital qubits. Here, we report on orbital-flop induced magnetoresistance anisotropy in CeSb. In the low temperature high magnetic-field driven ferromagnetic state, a series of additional minima appear in the angle-dependent magnetoresistance. These minima arise from the anisotropic magnetization originating from orbital-flops and from the enhanced electron scattering from magnetic multidomains formed around the first-order orbital-flop transition. The measured magnetization anisotropy can be accounted for with a phenomenological model involving orbital-flops and a spin-valve-like structure is used to demonstrate the viable utilization of orbital-flop phenomenon. Our results showcase a contribution of orbital behavior in the emergence of intriguing phenomena.

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Orbital Origin of Extremely Anisotropic Superconducting Gap in Nematic Phase of FeSe Superconductor

Abstract: These people contributed equally to the present work.

Cited by 82 publications

References 57 publications

Observation of orbital ordering and origin of the nematic order in FeSe

Observation of orbital ordering and origin of the nematic order in FeSe

Nematic Energy Scale and the Missing Electron Pocket in FeSe

Orbital-flop Induced Magnetoresistance Anisotropy in Rare Earth Monopnictide CeSb

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