Epitaxy-distorted spin-orbit Mott insulator in Sr<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>IrO<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>4</mml:mn></mml:msub></mml:math>thin films

Serrao, Claudy Rayan; Liu, Jian; Heron, John T.; Singh‐Bhalla, G.; Yadav, Ajay K.; Suresha, S. J.; Paull, R. J.; Yi, Di; Chu, Jiun‐Haw; Trassin, Morgan; Vishwanath, Ashvin; Arenholz, Elke; Frontera, C.; Železný, Jakub; Jungwirth, T.; Martí, X.; Ramesh, R.

doi:10.1103/physrevb.87.085121

Cited by 72 publications

(12 citation statements)

References 27 publications

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“…In this review, we focused on one material system, the square lattice iridate Sr 2 IrO 4 , for which the central issue has been whether it would display HTSC like cuprates. Even staying within this somewhat narrow scope, limited space did not allow us to touch upon different approaches to metallize Sr 2 IrO 4 through epitaxial thin films [137,138], high pressure [139,140], gating [141,142], and other chemical routes [143]. So far, the most promising results have been obtained from in situ doping used in combination with ARPES and STS, but the extreme surface sensitivity of these methods is a serious impediment to further scientific progress.…”

Section: Discussionmentioning

confidence: 99%

Square Lattice Iridates

Bertinshaw

Kim

Khaliullin

et al. 2019

Annu. Rev. Condens. Matter Phys.

100

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Over the last few years, Sr 2 IrO 4 , a single-layer member of the Ruddlesden-Popper series iridates, has received much attention as a close analog of cuprate high-temperature superconductors.Although there is not yet firm evidence for superconductivity, a remarkable range of cuprate phenomenology has been reproduced in electron-and hole-doped iridates including pseudogaps, Fermi arcs, and d-wave gaps. Further, a number of symmetry breaking orders reminiscent of those decorating the cuprate phase diagram have been reported using various experimental probes. We discuss how the electronic structures of Sr 2 IrO 4 through strong spin-orbit coupling leads to the low-energy physics that had long been unique to cuprates, what the similarities and differences between cuprates and iridates are, and how these advance the field of high-temperature superconductivity by isolating essential ingredients of superconductivity from a rich array of phenomena that surround it. Finally, we comment on the prospect of finding a new high-temperature superconductor based on the iridate series. b c a Sr O Ir a b c pseudospin-1/2 J a b FIG. 1. Crystal and magnetic structures of Sr 2 IrO 4 . (a) The crystal structure is based on Ref. [26] according to which the space group is I4 1 /acd. However, recent studies indicate that the symmetry is lower and most probably is I4 1 /a [27-29]. (b) Quasi-2D network of Ir and O. (c) The magnetic structure from Ref. [2]. II. MAPPING ONTO CUPRATE PHYSICSSoon after the discovery of HTSC in the cuprates, many complex oxides with a K 2 NiF 4 structure (isostructural to La 2 CuO 4 ) and its variants were searched for signs of superconductivity. Among these were Sr 2 RhO 4 and Sr 2 IrO 4 [30], which are "one-hole" systems, albeit with a t 2g -hole in the low-spin d 5 configuration as opposed to an e g -hole in cuprates. However, it was quickly apparent that 4d and 5d systems tend to be rather weakly correlated. In fact, Sr 2 RhO 4 is a Fermi liquid metal [31, 32] with a Fermi surface understood qualitatively in terms of a band structure calculated using density functional theory within the local density approximation (LDA) [33, 34]. Interestingly, the Fermi surfaces of Sr 2 RhO 4 and Sr 2 IrO 4 , calculated without SOC, are near indistinguishable due to their almost identical crystal structures with less than 1% difference in their lattice parameters [30]. A closer inspection, however, reveals that LDA does not accurately replicate the measured FermiX M X E-μ (eV) E-μ (eV) E-μ (eV) M X Γ Γ Γ Γ Γ Γ U ζ ζ μ wide band metal narrow J eff =1/2 band J eff =1/2 Mott state LDA+SOC LDA LDA+SOC+U t 2g band J eff =1/2 band J eff =3/2 band J eff =3/2 band J eff =1/2 UHB J eff =1/2 LHB FIG. 2. Illustration of the SOC driven Mott transition. Introduction of SOC splits off a narrow band near the Fermi level (orange solid lines), for which a moderate Coulomb interaction U ∼2 eV is sufficient to open a gap.observation of a significant gap reduction across T N , a typical Slater behavior, supports this viewpoint [42,43]. On th...

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Section: Discussionmentioning

confidence: 99%

Square Lattice Iridates

Bertinshaw

Kim

Khaliullin

et al. 2019

Annu. Rev. Condens. Matter Phys.

100

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“…There have been several studies of SIO under epitaxial strain condition, both from theory and experiments. Samples of SIO have been grown epitaxially on a number of substrates such as SrTiO 3 , LaAlO 3 , GdScO 3 , etc [11][12][13]. Resistivity and optical absorption measurements on these structures have shown that the Mott-Hubbard gap is preserved under epitaxial strain, but its magnitude can be tuned by varying the strain.…”

Section: Introductionmentioning

confidence: 99%

Electronic structure and optical properties of Sr₂IrO₄ under epitaxial strain

2019

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We study the modification of the electronic structure in the strong spin-orbit coupled Sr 2 IrO 4 by epitaxial strain using density-functional methods. Structural optimization shows that strain changes the internal structural parameters such as the Ir-O-Ir bond angle, which has an important effect on the band structure. An interesting prediction is the Γ−X crossover of the valence band maximum with strain, while the conduction minimum at M remains unchanged. This in turn suggests strong strain dependence of the transport properties for the hole-doped system, but not when the system is electron doped. Taking the measured value of the Γ−X separation for the unstrained case, we predict the Γ−X crossover of the valence band maximum to occur for the tensile epitaxial strain e xx ≈3%. A minimal tight-binding model within the J eff =1/2 subspace is developed to describe the main features of the band structure. The optical absorption spectra under epitaxial strain are computed using densityfunctional theory, which explains the observed anisotropy in the optical spectra with the polarization of the incident light. We show that the optical transitions between the Ir (d) states, which are dipole forbidden, can be explained in terms of the admixture of Ir (p) orbitals with the Ir (d) bands.

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“…Transition-metal oxides with partially filled d-electron states exhibit exceptionally rich electronic and magnetic phase diagrams. [1][2][3] Strong Coulomb interactions in narrow 3d-bands can lead to Mott insulators ground states. Moving down into 5d transition metal ions, the spatial extent of the orbitals increases, resulting in a stronger 5d-O:2p overlap.…”

Section: Introductionmentioning

confidence: 99%

“…Coulomb interactions or additional structural distortions introduce further splitting in that narrow J eff =1/2 band, opening up a charge gap, which can be manipulated by epitaxial strain. [4][5][6][7][8][9][10][11][12][13] The Ruddlesden-Popper (RP) series of strontium iridates, Sr n+1 Ir n O 3n+1 , features a localized-to-itinerant crossover from that insulating ground state of Sr 2 IrO 4 (with a two dimensional IrO 6 corner-sharing octahedral network characteristic of n = 1) to a correlated metallic state in the three dimensional perovskite SrIrO 3 (n = ∞). 14 This suggests the possibility of fine-tuning the charge gap across Sr n+1 Ir n O 3n+1 by growing high quality epitaxially strained thin films.…”

Section: Introductionmentioning

confidence: 99%

Epitaxial stabilization of pulsed laser deposited Srn+1IrnO3n+1 thin films: Entangled effect of growth dynamics and strain

et al. 2018

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The subtle balance of electronic correlations, crystal field splitting and spin-orbit coupling in layered Ir 4+ oxides can give rise to novel electronic and magnetic phases. Experimental progress in this field relies on the synthesis of epitaxial films of these oxides. However, the growth of layered iridates with excellent structural quality is a great experimental challenge. Here we selectively grow high quality single-phase films of Sr2IrO4, Sr3Ir2O7, and SrIrO3 on various substrates from a single Sr3Ir2O7 target by tuning background oxygen pressure and epitaxial strain. We demonstrate a complex interplay between growth dynamics and strain during thin film deposition. Such interplay leads to the stabilization of different phases in films grown on different substrates under identical growth conditions, which cannot be explained by a simple kinetic model. We further investigate the thermoelectric properties of the three phases and propose that weak localization is responsible for the low temperature activated resistivity observed in SrIrO3 under compressive strain.

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Epitaxy-distorted spin-orbit Mott insulator in Sr2IrO4thin films

Cited by 72 publications

References 27 publications

Square Lattice Iridates

Square Lattice Iridates

Electronic structure and optical properties of Sr₂IrO₄ under epitaxial strain

Epitaxial stabilization of pulsed laser deposited Srn+1IrnO3n+1 thin films: Entangled effect of growth dynamics and strain

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Epitaxy-distorted spin-orbit Mott insulator in Sr2IrO4thin films

Cited by 72 publications

References 27 publications

Square Lattice Iridates

Square Lattice Iridates

Electronic structure and optical properties of Sr2IrO4 under epitaxial strain

Epitaxial stabilization of pulsed laser deposited Srn+1IrnO3n+1 thin films: Entangled effect of growth dynamics and strain

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Product

Resources

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Electronic structure and optical properties of Sr₂IrO₄ under epitaxial strain