Unoccupied electronic structure of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi mathvariant="normal">Y</mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi mathvariant="normal">Ca</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:mi mathvariant="normal">Ti</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>investigated by inverse photoemission s

Arita, Masashi; Sato, Hitoshi; Higashi, Masayuki; Yoshikawa, Kouji; Shimada, Kenya; Nakatake, M.; Ueda, Yuko; Namatame, H.; Takeuchi, Masaki; Tsubota, Masami; Iga, Fumitoshi; Takabatake, Toshiro

doi:10.1103/physrevb.75.205124

Cited by 12 publications

(18 citation statements)

References 32 publications

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“…During the measurements, the sample temperature was maintained at 280 K under a vacuum of 3 × 10 −11 Torr. IPE measurements were carried out at HiSOR3435. The incident electron kinetic energy was set to 50 eV and an energy resolution was 0.9 eV.…”

Section: Methodsmentioning

confidence: 99%

Electronic Structure of the Kitaev Material α-RuCl3 Probed by Photoemission and Inverse Photoemission Spectroscopies

Sinn

Kim

et al. 2016

Sci Rep

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Recently, α-RuCl3 has attracted much attention as a possible material to realize the honeycomb Kitaev model of a quantum-spin-liquid state. Although the magnetic properties of α-RuCl3 have been extensively studied, its electronic structure, which is strongly related to its Kitaev physics, is poorly understood. Here, the electronic structure of α-RuCl3 was investigated by photoemission (PE) and inverse-photoemission (IPE) spectroscopies. The band gap was directly measured from the PE and IPE spectra and was found to be 1.9 eV, much larger than previously estimated values. Local density approximation (LDA) calculations showed that the on-site Coulomb interaction U could open the band gap without spin-orbit coupling (SOC). However, the SOC should also be incorporated to reproduce the proper gap size, indicating that the interplay between U and SOC plays an essential role. Several features of the PE and IPE spectra could not be explained by the results of LDA calculations. To explain such discrepancies, we performed configuration-interaction calculations for a RuCl63− cluster. The experimental data and calculations demonstrated that the 4d compound α-RuCl3 is a Jeff = 1/2 Mott insulator rather than a quasimolecular-orbital insulator. Our study also provides important physical parameters required for verifying the proposed Kitaev physics in α-RuCl3.

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Section: Methodsmentioning

confidence: 99%

Electronic Structure of the Kitaev Material α-RuCl3 Probed by Photoemission and Inverse Photoemission Spectroscopies

Sinn

Kim

et al. 2016

Sci Rep

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“…The cross section of the Ti 3d states can be largely enhanced around the Ti 3p-3d edge via the Fano-resonance between the standard IPES process and the Coster-Kronig Auger process [2,21]. Additionally, it has been reported that the energies of on-and off-resonance IPES are about 46 eV and 39 eV, respectively [21]. In the off-resonant IPES spectrum (E k = 40 eV), we observe three features; a broad shoulder structure in 0-3 eV, a relatively intense peak at ∼ 3.8 eV, and a broad hump structure in 8-12 eV.…”

Section: Experimental Methodsmentioning

confidence: 99%

Electronic structure of Mott-insulator CaCu 3 Ti 4 O 12 : Photoemission and inverse photoemission study

Iwataki

Yamazaki

et al. 2015

Solid State Communications

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We have performed the photoemission and inverse photoemission experiments to elucidate the origin of Mott insulating states in A-site ordered perovskite CaCu 3 Ti 4 O 12 (CCTO). Experimental results have revealed that Cu 3d-O 2p hybridized bands, which are located around the Fermi level in the prediction of the local-density approximation (LDA) band calculations, are actually separated into the upper Hubbard band at ∼ 1.5 eV and the lower Hubbard band at ∼ −1.7 eV with a band gap of ∼ 1.5-1.8 eV. We also observed that Cu 3d peak at ∼ −3.8 eV and Ti 3d peak at ∼ 3.8 eV are further away from each other than as indicated in the LDA calculations. In addition, it is found that the multiplet strucutre around −9 eV includes a considerable number of O 2p states. These observations indicate that the Cu 3d and Ti 3d electrons hybridized with the O 2p states are strongly correlated, which originates in the Mott-insulating states of CCTO.

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“…We refer the reader to [45,[54][55][56] for details on the static properties of the system obtained with DFT + DMFT and other approaches. The free-electron spectrum of YTiO 3 was obtained by using a tight-binding model with the parameters given in [54].…”

Section: Mott Insulator Ytiomentioning

confidence: 99%

Towards TDDFT for Strongly Correlated Materials

2016

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Abstract:We present some details of our recently-proposed Time-Dependent Density-Functional Theory (TDDFT) for strongly-correlated materials in which the exchange-correlation (XC) kernel is derived from the charge susceptibility obtained using Dynamical Mean-Field Theory (the TDDFT + DMFT approach). We proceed with deriving the expression for the XC kernel for the one-band Hubbard model by solving DMFT equations via two approaches, the Hirsch-Fye Quantum Monte Carlo (HF-QMC) and an approximate low-cost perturbation theory approach, and demonstrate that the latter gives results that are comparable to the exact HF-QMC solution. Furthermore, through a variety of applications, we propose a simple analytical formula for the XC kernel. Additionally, we use the exact and approximate kernels to examine the nonhomogeneous ultrafast response of two systems: a one-band Hubbard model and a Mott insulator YTiO 3 . We show that the frequency dependence of the kernel, i.e., memory effects, is important for dynamics at the femtosecond timescale. We also conclude that strong correlations lead to the presence of beats in the time-dependent electric conductivity in YTiO 3 , a feature that could be tested experimentally and that could help validate the few approximations used in our formulation. We conclude by proposing an algorithm for the generalization of the theory to non-linear response.

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Unoccupied electronic structure ofY1−xCaxTiO3investigated by inverse photoemission s

Cited by 12 publications

References 32 publications

Electronic Structure of the Kitaev Material α-RuCl3 Probed by Photoemission and Inverse Photoemission Spectroscopies

Electronic Structure of the Kitaev Material α-RuCl3 Probed by Photoemission and Inverse Photoemission Spectroscopies

Electronic structure of Mott-insulator CaCu 3 Ti 4 O 12 : Photoemission and inverse photoemission study

Towards TDDFT for Strongly Correlated Materials

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