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Mott transition and collective charge pinning in electron doped Sr_2IrO_4

Wang, K. and Bachar, N. and Teyssier, J. and Luo, W. and Rischau, C. W. and Scheerer, G. and de la Torre, A. and Perry, R. S. and Baumberger, F. and van der Marel, D. (2018) Mott transition and collective charge pinning in electron doped Sr_2IrO_4. Physical Review B, 98 (4). Art. No. 045107. ISSN 2469-9950. doi:10.1103/PhysRevB.98.045107.

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We studied the in-plane dynamic and static charge conductivity of electron doped Sr_2IrO_4 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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Alternate Title:Mott transition and collective charge pinning in electron doped Sr 2 IrO 4
Additional Information:© 2018 American Physical Society. (Received 16 January 2018; revised manuscript received 14 May 2018; published 5 July 2018) We gratefully acknowledge discussions with C. Berthod and T. Giamarchi. This project was supported by the Swiss National Science Foundation (projects 200021-153405 and 200021-162628.). K.W. and N.B. contributed equally to this work.
Group:Institute for Quantum Information and Matter
Funding AgencyGrant Number
Swiss National Science Foundation (SNSF)200021-153405
Swiss National Science Foundation (SNSF)200021-162628
Issue or Number:4
Record Number:CaltechAUTHORS:20180705-153353866
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:87572
Deposited By: George Porter
Deposited On:06 Jul 2018 14:53
Last Modified:15 Nov 2021 20:49

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