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Mott transition and collective charge pinning in electron doped Sr2IrO4

Perry, R. S.
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Published in Physical review. B, Condensed matter and materials physics. 2018, vol. 98, no. 045107, p. 1-12
Abstract We studied the in-plane dynamic and static charge conductivity of electron doped Sr2IrO4 using optical spectroscopy and DC transport measurements. The optical conductivity indicates that the pristine material is an indirect semiconductor with a direct Mott gap of 0.55 eV. Upon substitution of 2% La per formula unit the Mott gap is suppressed except in a small fraction of the material (15%) where the gap survives, and overall the material remains insulating. Instead of a zero energy mode (or Drude peak) we observe a soft collective mode (SCM) with a broad maximum at 40 meV. Doping to 10% increases the strength of the SCM, and a zero-energy mode occurs together with metallic DC conductivity. Further increase of the La substitution doesn't change the spectral weight integral up to 3 eV. It does however result in a transfer of the SCM spectral weight to the zero-energy mode, with a corresponding reduction of the DC resistivity for all temperatures from 4 to 300 K. The presence of a zero-energy mode signals that at least part of the Fermi surface remains ungapped at low temperatures, whereas the SCM appears to be caused by pinning a collective frozen state involving part of the doped electrons.
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Research groups Groupe Baumberger
Groupe Van der Marel
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WANG, Kai et al. Mott transition and collective charge pinning in electron doped Sr2IrO4. In: Physical Review. B, Condensed Matter, 2018, vol. 98, n° 045107, p. 1-12. doi: 10.1103/PhysRevB.98.045107 https://archive-ouverte.unige.ch/unige:109116

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Deposited on : 2018-10-12

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