Electron-Doped<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>Sr</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mi>IrO</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>: An Analogue of Hole-Doped Cuprate Superconductors Demonstrated by Scanning Tunneling Microscopy

Yan, Y. J.; Ren, Ming-Qiang; Xu, H. C.; Xie, Bin; Tao, Ruibao; Choi, Heekyung; Lee, N.; Choi, Young Jai; Zhang, T.; Feng, D. L.

doi:10.1103/physrevx.5.041018

Cited by 165 publications

(128 citation statements)

References 25 publications

(60 reference statements)

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“…4(e) at x ¼ 0.1 for ε ¼ 60 meV, which shows the destruction of the FS sections around X as in the clean case with long-range d-PSCO. More remarkable is the emergence of the fullfledged Fermi arcs as the folded part of the FS is destroyed by the scattering due to spatially fluctuating pseudospin current, in good agreement with the observed Fermi arcs and d-wave-like pseudogaps by ARPES and STM in heavily surface-K-doped iridates [28][29][30]. Figure 4(f) is a spectral intensity plot of the FS when the disordered pseudospin currents fluctuate spatially around a nonzero mean of the d-PSCO with Δ d ¼ AE30 meV to account for averaging over two domains.…”

supporting

confidence: 84%

“…We argue that the hidden order has an electronic origin and can be generated spontaneously by the intersite Coulomb interactions due to the large spatial extent of the iridium 5d orbitals, turning the metallic phase of the iridates into an electron-doped quasi-2D Dirac semimetal. These findings provide new insights and perspectives for understanding the possible emergence of a superconducting phase [29,30].…”

mentioning

confidence: 78%

“…In high-quality undoped Sr 2 IrO 4 samples, the most recent ARPES experiment [21] was able to resolve the broad spectra in the canted AFM insulator near the high-symmetry point X ¼ ðπ; 0Þ and ð0; πÞ observed in earlier experiments [1,[22][23][24][25] and reveal a degeneracy splitting of the quasiparticle (QP) dispersion, indicative of a symmetry-breaking hidden electronic order. Electron doping the AFM insulator has been achieved by La substitution (Sr 2−x La x IrO 4 ) [21,26], oxygen deficiency (Sr 2 IrO 4−δ ) [27], and in situ potassium surface doping [28][29][30]. ARPES measurements showed that the collapse of the AFM insulating gap gives rise to a paramagnetic (PM) metallic state with Fermi surface (FS) pockets for bulk electron doping at x ¼ 0.1 [21] and to Fermi arcs [28] with d-wave-like pseudogaps around X [21,29] under surface doping, in striking analogy to the high-T c cuprates.…”

mentioning

confidence: 99%

“…4(c)] protected by the nonsymmorphic space group symmetries [60]. Thus, the metallic state of the iridates behaves as an electron-doped quasi-2D Dirac semimetal, which may play an essential role for studying electronic pairing and the possible emergence of superconductivity in Sr 2−x La x IrO 4 [29,30].…”

mentioning

confidence: 99%

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Correlation Effects and Hidden Spin-Orbit Entangled Electronic Order in Parent and Electron-Doped Iridates Sr2IrO4

Zhou¹,

Jiang²,

Chen³

et al. 2017

Phys. Rev. X

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Analogs of the high-T c cuprates have been long sought after in transition metal oxides. Because of the strong spin-orbit coupling, the 5d perovskite iridates Sr 2 IrO 4 exhibit a low-energy electronic structure remarkably similar to the cuprates. Whether a superconducting state exists as in the cuprates requires understanding the correlated spin-orbit entangled electronic states. Recent experiments discovered hidden order in the parent and electron-doped iridates, some with striking analogies to the cuprates, including Fermi surface pockets, Fermi arcs, and pseudogap. Here, we study the correlation and disorder effects in a five-orbital model derived from the band theory. We find that the experimental observations are consistent with a d-wave spin-orbit density wave order that breaks the symmetry of a joint twofold spin-orbital rotation followed by a lattice translation. There is a Berry phase and a plaquette spin flux due to spin procession as electrons hop between Ir atoms, akin to the intersite spin-orbit coupling in quantum spin Hall insulators. The associated staggered circulating J eff ¼ 1=2 spin current can be probed by advanced techniques of spin-current detection in spintronics. This electronic order can emerge spontaneously from the intersite Coulomb interactions between the spatially extended iridium 5d orbitals, turning the metallic state into an electron-doped quasi-2D Dirac semimetal with important implications on the possible superconducting state suggested by recent experiments. . The canting of the inplane magnetic moments tracks the θ ≃ 11°staggered IrO 6 octahedra rotation about the c axis [3][4][5][6] due to the strong spin-orbit coupling (SOC). The AFM insulating state arises from a novel interplay between SOC and electron correlation most easily understood near the atomic limit. Ir 4þ has a 5d 5 configuration. The 5 electrons occupy the lower threefold t 2g orbitals separated from the higher twofold e g orbitals by the cubic crystal field Δ c . The strong atomic SOC λ SOC splits the t 2g orbitals into a low-lying J eff ¼ 3=2 spin-orbit multiplet occupied by 4 electrons and a singly occupied J eff ¼ 1=2 doublet. Assuming λ SOC and Δ c are sufficiently large compared to the relevant bandwidths when Sr 2 IrO 4 crystalizes, a single J eff ¼ 1=2 band is half filled and can be driven by a moderate local Coulomb repulsion U to an AFM Mott insulating state [1,2,7]. The nature of the spin-orbit entangled insulating state has been studied using the localized picture based on the J eff ¼ 1=2 pseudospin anisotropic Heisenberg model [7][8][9][10][11], the three-orbital Hubbard model for the t 2g electrons with SOC [12][13][14][15], and the microscopic correlated density functional theory such as the LDA þ U and GGA þ U [1, [16][17][18]. Moreover, carrier doping the AFM insulating state was proposed to potentially realize a 5d t 2g -electron analog of the 3d e g -electron high-T c cuprate superconductors [8,12,13,19,20].In this work, we study the hidden order in both stoichiometric and electron-doped Sr...

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supporting

confidence: 84%

mentioning

confidence: 78%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Correlation Effects and Hidden Spin-Orbit Entangled Electronic Order in Parent and Electron-Doped Iridates Sr2IrO4

Zhou¹,

Jiang²,

Chen³

et al. 2017

Phys. Rev. X

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“…A recent angle resolved photoemission (ARPES) study found an anisotropic pseudogap in Sr 2−y La y IrO 4 [6]. ARPES [7] and STM [8] experiments on K-covered Sr 2 IrO 4 further reported evidence for a d-wave gap closing at 30-50 K. In addition * dirk.vandermarel@unige.ch a degeneracy splitting of the bands near (π,0) was found in ARPES experiments [6] and a hidden order parameter has been claimed based on observations with optical second harmonic generation [9]. These observations have lead to different mutually exclusive speculations as to the nature of this state of matter, in particular superconducting fluctuations [7] and a d-wave pseudospin-current ordered state [10].…”

Section: Introductionmentioning

confidence: 97%

Mott transition and collective charge pinning in electron doped Sr2IrO4

et al. 2018

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We studied the in-plane dynamic and static charge conductivity of electron doped Sr 2 IrO 4 using optical spectroscopy and DC transport measurements. The optical conductivity indicates that the pristine material is an indirect semiconductor with a direct Mott gap of 0.55 eV. Upon substitution of 2% La per formula unit the Mott gap is suppressed except in a small fraction of the material (15%) where the gap survives, and overall the material remains insulating. Instead of a zero energy mode (or Drude peak) we observe a soft collective mode (SCM) with a broad maximum at 40 meV. Doping to 10% increases the strength of the SCM, and a zero-energy mode occurs together with metallic DC conductivity. Further increase of the La substitution doesn't change the spectral weight integral up to 3 eV. It does however result in a transfer of the SCM spectral weight to the zero-energy mode, with a corresponding reduction of the DC resistivity for all temperatures from 4 to 300 K. The presence of a zero-energy mode signals that at least part of the Fermi surface remains ungapped at low temperatures, whereas the SCM appears to be caused by pinning a collective frozen state involving part of the doped electrons.

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