Optical study of the electronic structure and correlation effects in K<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mrow><mml:mn>0.49</mml:mn></mml:mrow></mml:msub></mml:math>RhO<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>

Okazaki, Renji; Nishina, Yasuo; Yasui, Yukihiko; Shibasaki, S.; Terasaki, Ichiro

doi:10.1103/physrevb.84.075110

Cited by 21 publications

(27 citation statements)

References 40 publications

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“…In this rhodate, resistivity measurements showed no sign of density waves [24,25]; optical study suggested weaker electron correlation and smaller carrier effective mass compared to those in Na x CoO 2 [26]. Thus, the K x RhO 2 system is ideal to help disentangle the correlation effects and unravel the origin of the large thermopower.…”

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confidence: 90%

Large thermopower from dressed quasiparticles in the layered cobaltates and rhodates

Chen

Zong

et al. 2017

Phys. Rev. B

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confidence: 90%

Large thermopower from dressed quasiparticles in the layered cobaltates and rhodates

Chen

Zong

et al. 2017

Phys. Rev. B

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“…To clarify a precise role of correlated Co 3d electrons for the intriguing electronic properties in this compound, it is quite valuable to substitute the Co ions by isovalent transition-metal elements with different orbital size and correlation effect [28][29][30]. The physical properties of polycrystalline samples of isovalent Rh-substituted Ca 3 Co 4 O 9 have been recently examined for this purpose [31], however, the polycrystalline samples have an unavoidable extrinsic effect on the charge transport such as the boundary scattering.…”

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confidence: 99%

Thermoelectric transport in the layered Ca3Co4–xRhxO9 single crystals

Ikeda

Saito

Okazaki

2016

Journal of Applied Physics

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We have examined an isovalent Rh substitution effect on the transport properties of the thermoelectric oxide Ca 3 Co 4 O 9 using single-crystalline form. With increasing Rh content x, both the electrical resistivity and the Seebeck coefficient change systematically up to x = 0.6 for Ca 3 Co 4−x Rh x O 9 samples. In the Fermi-liquid regime where the resistivity behaves as ρ = ρ 0 + AT 2 around 120 K, the A value decreases with increasing Rh content, indicating that the correlation effect is weakened by Rh 4d electrons with extended orbitals. We find that, in contrast to such a weak correlation effect observed in the resistivity of Rh-substituted samples, the low-temperature Seebeck coefficient is increased with increasing Rh content, which is explained with a possible enhancement of a pseudogap associated with the short-range order of spin density wave. In high-temperature range above room temperature, we show that the resistivity is largely suppressed by Rh substitution while the Seebeck coefficient becomes almost temperature-independent, leading to a significant improvement of the power factor in Rh-substituted samples. This result is also discussed in terms of the differences in the orbital size and the associated spin state between Co 3d and Rh 4d electrons.

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“…3 Compared to Na x CoO 2 , K x RhO 2 system has a larger crystal-field splitting between e g and t 2g bands and a broader 4d-electron bandwidth. 4 The K content also affects strongly the crystal structure which in turn modifies the thermoelectric, electrical, and magnetic transport properties. Saeed et al 5 calculated the electronic structure of K x RhO 2 (x = 0.5 and x = 7/8) showing that K x RhO 2 is a potential thermoelectric material.…”

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Lattice dynamics of KxRhO2 single crystals

Zhang

Dong

et al. 2015

AIP Advances

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A series of crystals KxRhO2 (x = 0.72, 0.63, 0.55, 0.39, and 0.24) have been synthesized and their vibrational properties have been studied by first principles calculations, Raman spectroscopy, and inelastic neutron scattering. The measured vibrational spectra of KxRhO2 for x = 0.72 and 0.63 are consistent with the theoretical prediction for the stoichiometric KRhO2. For samples with x = 0.55, 0.39 and 0.24, extra vibrational modes have been observed and they are believed to be due to the symmetry reduction and the loss of translational symmetry induced by K disorder. The good agreement was found for the phonon density of states among the Raman spectroscopic observations, inelastic neutron scattering and the first principles calculations, as an evidence for the generation of structure disorder by K deficiency.

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Optical study of the electronic structure and correlation effects in K0.49RhO2

Cited by 21 publications

References 40 publications

Large thermopower from dressed quasiparticles in the layered cobaltates and rhodates

Large thermopower from dressed quasiparticles in the layered cobaltates and rhodates

Thermoelectric transport in the layered Ca3Co4–xRhxO9 single crystals

Lattice dynamics of KxRhO2 single crystals

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