Optical properties of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>TlNi</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mspace width="0.16em" /><mml:msub><mml:mi>Se</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>: Observation of pseudogap formation

Wang, X. B.; Wang, H. P.; Wang, Hangdong; Fang, Minghu; Wang, N. L.

doi:10.1103/physrevb.92.245129

Cited by 7 publications

(7 citation statements)

References 32 publications

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“…On the other hand, the hopping parameters for SrRu 2 O 6 , as calculated in Ref. [11], are similar to those in Na 2 IrO 3 , in the sense that again t 1 = 300 meV is by far the largest hopping, and the only other sizeable hoppings are t 1 = 160 meV and −t 2 ≈ 100 − 110 meV. Note that here |t 2 | is again about 1/3 of t 1 .…”

supporting

confidence: 74%

Localized itinerant electrons and unique magnetic properties ofSrRu2O6

Streltsov¹,

Mazin²,

Foyevtsova³

2015

Phys. Rev. B

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SrRu2O6 has unique magnetic properties. It is characterized by a very high Néel temperature, despite its quasi-two-dimensional structure, and has a magnetic moment more than twice reduced compared to the formal ionic count. First principles calculations show that only an ideal Néel ordering in the Ru plane is possible, with no other metastable magnetic solutions, and, highly unusually, yield dielectric gaps for both antiferromagnetic and nonmagnetic states. We demonstrate that this strange behavior is the result of the formation of very specific electronic objects, recently suggested for a geometrically similar Na2IrO3 compound, whereby each electron is well localized on a particular Ru6 hexagon, and completely delocalized over the corresponding six Ru sites, thus making the compound both strongly localized and highly itinerant.

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supporting

confidence: 74%

Localized itinerant electrons and unique magnetic properties ofSrRu2O6

Streltsov¹,

Mazin²,

Foyevtsova³

2015

Phys. Rev. B

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“…For other fillings, e.g., four or two electrons per transition metal site, one may expect two other transitions, which can be, however, suppressed not due to the symmetry or parity reasons, but because of a particular ratio between hopping parameters. E.g., in both RuCl 3 and SrRu 2 O 6 , as well as in Na 2 IrO 3 , the hopping t ′ 2 was found to be of order of −t ′ 1 /3 [11,23], which will result in a strong suppression of the E 1u → A 1g transition. If one chose t ′ 1 = 0.3 eV and t ′ 2 = −0.1 eV as it was estimated for SrRu 2 O 6 by Wang et al [23], then indeed f E1u,A1g ∼ 0, while f B1u,E2g =f E2g,E1u =0.356.…”

Section: Pacs Numbersmentioning

confidence: 96%

Spectroscopic signatures of molecular orbitals in transition metal oxides with a honeycomb lattice

2016

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A tendency to form benzene-like molecular orbitals has been recently shown to be a common feature of the 4d and 5d transition metal oxides with a honeycomb lattice. This tendency competes with other interactions such as the spin-orbit coupling and Hubbard correlations, and can be partially or completely suppressed. In the calculations, SrRu2O6 presents the cleanest, so far, case of well-formed molecular orbitals, however, direct experimental evidence for or against this proposition has been missing. In this paper, we show that combined photoemission and optical studies can be used to identify molecular orbitals in SrRu2O6. Symmetry-driven election selection rules suppress optical transitions between certain molecular orbitals, while photoemission and inverse photoemission measurements are insensitive to them. Comparing the photoemission and optical conductivity spectra one should be able to observe clear signatures of molecular orbitals. PACS numbers:Introduction. Low dimensional ruthenates with a honeycomb lattice have been attracting a lot of attention in recent years. α−RuCl 3 , which has one hole in the t 2g manifold, shows hallmarks of Kitaev physics[1, 2], Li 2 RuO 3 with two t 2g holes dimerizes in the lowtemperature phase [3,4] and exhibits a valence bond liquid behavior at high temperatures [5,6], while SrRu 2 O 6 with a half-filled t 2g band shows rather unusual magnetic properties [7]. It has been argued [8] that the physics of these compounds is underscored by competition between the spin-orbit coupling and Hubbard correlations, on one side, direct Ru-Ru one-electron hopping, on the other side, and O-assisted indirect hopping that leads to formation of molecular orbitals (MO), on the third side [9]. Ab initio calculations show that MOs appear to dominate in the last compound [8]. In the first two they are mostly suppressed, but at least in α−RuCl 3 (and in a similar compound, Na 2 IrO 3 ) they manifest themselves via an anomalously large third-neighbor coupling [10].

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“…Since at T N SrTcO 3 has the ideal perovskite symmetry (space group Pm3m) [30], the three t 2g orbitals are degenerate and thus half-filled. In SrRu 2 O 6 the RuO 6 octahedra are stretched along the c-axis, but the C 3v symmetry still protects the t 2g orbital degeneracy [31]. Hence, the 3 t 2g orbitals are also half-filled.…”

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confidence: 93%

Itinerant Antiferromagnetism in RuO2

et al. 2017

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Bulk rutile RuO2 has long been considered a Pauli paramagnet. Here we report that RuO2 exhibits a hitherto undetected lattice distortion below approximately 900 K. The distortion is accompanied by antiferromagnetic order up to at least 300 K with a small room temperature magnetic moment of approximately 0.05 µB as evidenced by polarized neutron diffraction. Density functional theory plus U (DFT+U ) calculations indicate that antiferromagnetism is favored even for small values of the Hubbard U of the order of 1 eV. The antiferromagnetism may be traced to a Fermi surface instability, lifting the band degeneracy imposed by the rutile crystal field. The combination of high Néel temperature and small itinerant moments make RuO2 unique among ruthenate compounds and among oxide materials in general.PACS numbers: 74.70. Pq,75.50.Ee,75.30.Fv Theories of magnetism in 3d transition metal oxides (TMOs) are usually framed in the context of strong Coulomb repulsions and Hund's rule coupling in the 3d orbitals of the transition metal cation, and their covalent bonding with the oxygen 2p orbitals. Strong on-site electron interactions tend to inhibit double occupancy of the 3d orbital and the overall Coulomb energy of the crystal is lowered by localizing the valence charge of the cation. Covalent bonding delocalizes the d-electron charge and thus lowers the kinetic energy. The former mechanism favors the formation of local magnetic moments while the latter decreases the moment but increases the exchange coupling between the moments through virtual hopping processes. In particular, the anion-mediated KramersAnderson "superexchange" between half-filled 3d orbitals often gives rise to strong antiferromagnetism. Many 3d transition metal oxides can be classified as antiferromagnetic Mott insulators where the on-site Coulomb repulsion U exceeds the electronic band width W . has been reported to host hightemperature antiferromagnetism with a Néel temperature T N = 563 K [5]. Ruthenium dioxide (RuO 2 ), on the other hand, has been thought to fall in line with other binary 4d transition metal oxides [6]; it is a good metal [7] and believed to be Pauli paramagnetic [8]. From the point of view of correlated electron physics and magnetism, RuO 2 seems to be one of the least interesting 4d TMOs. From a technology perspective, however, RuO 2 is by far one of the most important oxides. It has numerous applications in electro-and heterogeneous catalysis, as electrode material in electrolytic cells, supercapacitors, batteries and fuel cells, and as diffusion barriers in microelectronic devices [9]. It owes its usefulness in part to its relatively high electrical conductivity combined with its excellent thermal and chemical stability [10]. For the technological applications little attention has been paid to the potential role of magnetism (with the exception of Ref.[11]), presumably because magnetism is generally believed to be non-existent in bulk RuO 2 .In this letter we report on the finding that RuO 2 is distorted from the rutile symmetry...

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Optical properties ofTlNi2Se2: Observation of pseudogap formation

Cited by 7 publications

References 32 publications

Localized itinerant electrons and unique magnetic properties ofSrRu2O6

Localized itinerant electrons and unique magnetic properties ofSrRu2O6

Spectroscopic signatures of molecular orbitals in transition metal oxides with a honeycomb lattice

Itinerant Antiferromagnetism in RuO2

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