Intrinsic charge dynamics in high-Tc AFeAs(O,F) superconductors

A. Charnukha; D. Pröpper; N. D. Zhigadlo; M. Naito; M. Schmidt; Z. Wang; J. Deisenhofer; A. Loidl; B. Keimer; A. V. Boris; D. N. Basov

doi:10.1103/physrevlett.120.087001

arXiv · 1804.02021

Intrinsic charge dynamics in high-Tc AFeAs(O,F) superconductors

A. Charnukha·D. Pröpper·N. D. Zhigadlo·M. Naito·M. Schmidt·Z. Wang·J. Deisenhofer·A. Loidl·B. Keimer·A. V. Boris·D. N. Basov

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Abstract

We report the first determination of the in-plane complex optical conductivity of 1111 high-Tc superconducting iron oxypnictide single crystals PrFeAsO0.6F0.35 and thin films SmFeAsO1-xFx by means of bulk-sensitive conventional and micro-focused infrared spectroscopy, ellipsometry, and time-domain THz transmission spectroscopy. A strong itinerant contribution is found to exhibit a dramatic difference in coherence between the crystal and the film. Using extensive temperature-dependent measurements of THz transmission we identify a previously undetected 2.5-meV collective mode in the optical conductivity of SmFeAs(O,F), which is strongly suppressed at Tc and experiences an anomalous T-linear softening and narrowing below T*=110K>>Tc. The suppression of the infrared absorption in the superconducting state reveals a large optical superconducting gap with a similar gap ratio 2D=kBTc=7 in both materials, indicating strong pairing.

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A. Charnukha, D. Pröpper, N. D. Zhigadlo, M. Naito, M. Schmidt, Z. Wang, J. Deisenhofer, A. Loidl, B. Keimer, A. V. Boris, D. N. Basov. 2018-04-05. Intrinsic charge dynamics in high-Tc AFeAs(O,F) superconductors. https://doi.org/10.1103/physrevlett.120.087001

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