Ambipolar suppression of superconductivity by ionic gating in optimally doped BaFe2(As,P)2 ultrathin films

Erik Piatti, Takafumi Hatano, Dario Daghero, Francesco Galanti, Claudio Gerbaldi, Salvatore Guastella, Chiara Portesi, Ibuki Nakamura, Ryosuke Fujimoto, Kazumasa Iida, Hiroshi Ikuta, and Renato S. Gonnelli
Phys. Rev. Materials 3, 044801 – Published 15 April 2019
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Abstract

Superconductivity (SC) in the Ba-122 family of iron-based compounds can be controlled by aliovalent or isovalent substitutions, applied external pressure, and strain, the combined effects of which are sometimes studied within the same sample. Most often, the result is limited to a shift of the SC dome to different doping values. In a few cases, the maximum SC transition at optimal doping can also be enhanced. In this work, we study the combination of charge doping together with isovalent P substitution and strain by performing ionic gating experiments on BaFe2(As0.8P0.2)2 ultrathin films. We show that the polarization of the ionic gate induces modulations to the normal-state transport properties that can be mainly ascribed to surface charge doping. We demonstrate that ionic gating can only shift the system away from the optimal conditions, as the SC transition temperature is suppressed by both electron and hole doping. We also observe a broadening of the resistive transition, which suggests that the SC order parameter is modulated nonhomogeneously across the film thickness, in contrast with earlier reports on charge-doped standard BCS superconductors and cuprates.

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  • Received 8 October 2018
  • Revised 27 February 2019

DOI:https://doi.org/10.1103/PhysRevMaterials.3.044801

©2019 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Erik Piatti1, Takafumi Hatano2, Dario Daghero1, Francesco Galanti1, Claudio Gerbaldi1, Salvatore Guastella1, Chiara Portesi3, Ibuki Nakamura2, Ryosuke Fujimoto2, Kazumasa Iida2, Hiroshi Ikuta2, and Renato S. Gonnelli1,*

  • 1Department of Applied Science and Technology, Politecnico di Torino, 10129 Torino, Italy
  • 2Department of Materials Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan
  • 3INRiM–Istituto Nazionale di Ricerca Metrologica, 10135 Torino, Italy

  • *renato.gonnelli@polito.it

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Vol. 3, Iss. 4 — April 2019

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