Dresden 2017 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 19: Poster Session: Correlated Electrons 1

TT 19.31: Poster

Montag, 20. März 2017, 15:00–19:00, P2-EG

Optical conductivity of Na₂IrO₃ supporting the j=1/2 scenario — •Philipp Warzanowski¹, Nick Borgwardt¹, Maria Hermanns², Petra Becker³, Paul van Loosdrecht¹, and Markus Grüninger¹ — ¹II. Physikalisches Institut, Universität zu Köln — ²Institut für theoretische Physik, Universität zu Köln — ³Abteilung Kristallographie, Institut für Geologie und Mineralogie, Universität zu Köln

Na₂IrO₃ is widely discussed as a realization of the Heisenberg-Kitaev model with local j=1/2 moments. Challenging the j=1/2 scenario, a description in terms of quasimolecular orbitals (QMOs) with electrons delocalized over individual Ir₆ rings has been suggested [1]. Our infrared transmittance data in the vicinity of the gap for electron-hole excitations provide a litmus test for the underlying microscopic physics, since theoretical predictions based on either QMOs [2] or local j=1/2 moments [3] disagree strongly on the spectral weight of the lowest optical excitation band. We find that the spectral weight below about 0.7 eV is much smaller than reported previously, supporting the j=1/2 scenario. Moreover, we reveal a series of small absorption features around the onset of electron-hole excitations, pointing towards a mixing of electron-hole excitations with local spin-orbital excitations.

[1] I.I. Mazin et al., Phys. Rev. Lett. 109, 197201 (2012)

[2] Y. Li et al., Phys. Rev. B 91, 161101(R) (2015)

[3] B.H. Kim, G. Khaliullin, and B.I. Min, Phys. Rev. B 89, 081109(R) (2014)