Optical signatures of spin-orbit exciton in bandwidth-controlled S r2Ir O4 epitaxial films via high-concentration Ca and Ba doping

M. Souri; B. H. Kim; J. H. Gruenewald; J. G. Connell; J. Thompson; J. Nichols; J. Terzic; B. I. Min; G. Cao; J. W. Brill; A. Seo

doi:10.1103/PhysRevB.95.235125

Optical signatures of spin-orbit exciton in bandwidth-controlled S r2Ir O4 epitaxial films via high-concentration Ca and Ba doping

M. Souri, B. H. Kim, J. H. Gruenewald, J. G. Connell, J. Thompson, J. Nichols, J. Terzic, B. I. Min, G. Cao, J. W. Brill, A. Seo

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17 Scopus citations

Abstract

We have investigated the electronic and optical properties of (Sr1-xCax)2IrO4 (x=0-0.375) and (Sr1-yBay)2IrO4 (y=0-0.375) epitaxial thin films, in which the bandwidth is systematically tuned via chemical substitutions of Sr ions by Ca and Ba. Transport measurements indicate that the thin-film series exhibits insulating behavior, similar to the Jeff=1/2 spin-orbit Mott insulator Sr2IrO4. As the average A-site ionic radius increases from (Sr1-xCax)2IrO4 to (Sr1-yBay)2IrO4, optical conductivity spectra in the near-infrared region shift to lower energies, which cannot be explained by the simple picture of well-separated Jeff=1/2 and Jeff=3/2 bands. We suggest that the two-peak-like optical conductivity spectra of the layered iridates originates from the overlap between the optically forbidden spin-orbit exciton and the intersite optical transitions within the Jeff=1/2 band. Our experimental results are consistent with this interpretation as implemented by a multiorbital Hubbard model calculation: namely, incorporating a strong Fano-like coupling between the spin-orbit exciton and intersite d-d transitions within the Jeff=1/2 band.

Original language	English
Article number	235125
Journal	Physical Review B
Volume	95
Issue number	23
DOIs	https://doi.org/10.1103/PhysRevB.95.235125
State	Published - Jun 14 2017

Bibliographical note

Publisher Copyright:
© 2017 American Physical Society.

Funding

We thank C. H. Sohn for useful discussions and valuable comments. We acknowledge the support of National Science Foundation Grants No. DMR-1454200 for thin-film synthesis and characterizations, No. DMR-1265162 and No. DMR-1712101 for target synthesis, and No. DMR-1262261 for infrared spectroscopy. B.H.K. acknowledges support from the RIKEN iTHES Project for the numerical calculations.

Funders	Funder number
National Science Foundation (NSF)	1454200, DMR-1265162, DMR-1262261, DMR-1454200, DMR-1712101
RIKEN

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Condensed Matter Physics

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10.1103/PhysRevB.95.235125

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title = "Optical signatures of spin-orbit exciton in bandwidth-controlled S r2Ir O4 epitaxial films via high-concentration Ca and Ba doping",

abstract = "We have investigated the electronic and optical properties of (Sr1-xCax)2IrO4 (x=0-0.375) and (Sr1-yBay)2IrO4 (y=0-0.375) epitaxial thin films, in which the bandwidth is systematically tuned via chemical substitutions of Sr ions by Ca and Ba. Transport measurements indicate that the thin-film series exhibits insulating behavior, similar to the Jeff=1/2 spin-orbit Mott insulator Sr2IrO4. As the average A-site ionic radius increases from (Sr1-xCax)2IrO4 to (Sr1-yBay)2IrO4, optical conductivity spectra in the near-infrared region shift to lower energies, which cannot be explained by the simple picture of well-separated Jeff=1/2 and Jeff=3/2 bands. We suggest that the two-peak-like optical conductivity spectra of the layered iridates originates from the overlap between the optically forbidden spin-orbit exciton and the intersite optical transitions within the Jeff=1/2 band. Our experimental results are consistent with this interpretation as implemented by a multiorbital Hubbard model calculation: namely, incorporating a strong Fano-like coupling between the spin-orbit exciton and intersite d-d transitions within the Jeff=1/2 band.",

author = "M. Souri and Kim, {B. H.} and Gruenewald, {J. H.} and Connell, {J. G.} and J. Thompson and J. Nichols and J. Terzic and Min, {B. I.} and G. Cao and Brill, {J. W.} and A. Seo",

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doi = "10.1103/PhysRevB.95.235125",

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AU - Souri, M.

AU - Kim, B. H.

AU - Gruenewald, J. H.

AU - Connell, J. G.

AU - Thompson, J.

AU - Nichols, J.

AU - Terzic, J.

AU - Min, B. I.

AU - Cao, G.

AU - Brill, J. W.

AU - Seo, A.

PY - 2017/6/14

Y1 - 2017/6/14

N2 - We have investigated the electronic and optical properties of (Sr1-xCax)2IrO4 (x=0-0.375) and (Sr1-yBay)2IrO4 (y=0-0.375) epitaxial thin films, in which the bandwidth is systematically tuned via chemical substitutions of Sr ions by Ca and Ba. Transport measurements indicate that the thin-film series exhibits insulating behavior, similar to the Jeff=1/2 spin-orbit Mott insulator Sr2IrO4. As the average A-site ionic radius increases from (Sr1-xCax)2IrO4 to (Sr1-yBay)2IrO4, optical conductivity spectra in the near-infrared region shift to lower energies, which cannot be explained by the simple picture of well-separated Jeff=1/2 and Jeff=3/2 bands. We suggest that the two-peak-like optical conductivity spectra of the layered iridates originates from the overlap between the optically forbidden spin-orbit exciton and the intersite optical transitions within the Jeff=1/2 band. Our experimental results are consistent with this interpretation as implemented by a multiorbital Hubbard model calculation: namely, incorporating a strong Fano-like coupling between the spin-orbit exciton and intersite d-d transitions within the Jeff=1/2 band.

AB - We have investigated the electronic and optical properties of (Sr1-xCax)2IrO4 (x=0-0.375) and (Sr1-yBay)2IrO4 (y=0-0.375) epitaxial thin films, in which the bandwidth is systematically tuned via chemical substitutions of Sr ions by Ca and Ba. Transport measurements indicate that the thin-film series exhibits insulating behavior, similar to the Jeff=1/2 spin-orbit Mott insulator Sr2IrO4. As the average A-site ionic radius increases from (Sr1-xCax)2IrO4 to (Sr1-yBay)2IrO4, optical conductivity spectra in the near-infrared region shift to lower energies, which cannot be explained by the simple picture of well-separated Jeff=1/2 and Jeff=3/2 bands. We suggest that the two-peak-like optical conductivity spectra of the layered iridates originates from the overlap between the optically forbidden spin-orbit exciton and the intersite optical transitions within the Jeff=1/2 band. Our experimental results are consistent with this interpretation as implemented by a multiorbital Hubbard model calculation: namely, incorporating a strong Fano-like coupling between the spin-orbit exciton and intersite d-d transitions within the Jeff=1/2 band.

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Optical signatures of spin-orbit exciton in bandwidth-controlled S r2Ir O4 epitaxial films via high-concentration Ca and Ba doping

Abstract

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