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The 293rd SPring-8 Seminar

Subject/Contents Electron-phonon coupling in high temperature superconducting oxychlorides, a light element model for cuprates
Period from 16:00 to 17:00 Wed., Nov 13 , 2019
Venue Middle-size lecture hall in Public Relations Center
Format Lecture

Speaker: Dr. Matteo d’Astuto

Language: English

Affiliation: CNRS (France)

Title: Electron-phonon coupling in high temperature superconducting oxychlorides, a light element model for cuprates

The copper oxychloride cuprate Ca2CuO2Cl2 (CCOC) system, with vacancy or Na doping on the Ca site, is unique among the high temperature superconducting cuprates (HTSCs) since it: lacks high Z atoms; has a simple I4/mmm 1-layer structure, typical of 214 (LSCO) cuprates, but which is stable at all doping and temperatures; and has a strong 2D character due to the replacement of apical oxygen with chlorine [1]. It also shows a remarkable phase diagram, with a superconducting Tc growing to the optimal doping without any minimum around 1/8 doping, despite the observation of charge modulations by by near-field spectro-microscopy [2]. Due to the reduced number of electrons, advanced calculations that incorporate correlation effects, such as quantum Monte Carlo [3], are easier, but relatively little is known about CCOC from an experimental point of view. We are now filling this gap by a comprehensive experimental study covering the whole phase diagram, in particular of the (para)magnon [4] and phonon dispersion [5]. In this talk, we will focus on the phonons modes, particularly of the stretching of the Cu-O bond, as the possible responsible of the very large isotope effect in underdoped cuprate [6]. We will show how this can be linked to anomalies in the dispersion of Cu-O bond stretching mode, and most probably to the kink affecting ARPES bands at the same energy [7], and how RIXS unveil a strong electron-phonon coupling with that mode [8]. We will show how simple DFT fail to describe the mode dispersion [5], and henceforth its coupling with charge carriers. Finally, we will show that the enhancement of the electron-phonon coupling around 1/8 doping is caused by charge order proximity, which is particularly interesting in the oxychlorides, and the needs for a measurement of the bare phonon dispersion in that compound, that will take place in a forthcoming experiment at BL35XU(SPring-8).

[1] Z. Hiroi, N. Kobayashi, M. Takano, Nature vol. 371, 139 (1994); Y. Kohsaka et al. JACS vol.124, 12275 (2002)
[2] T. Hanaguri et al. Nature vol. 430, 1001 (2004); K. Fujita et al. PNAS vol. 111, E3026 (2014)
[3] K. Foyevtsova et al., Phys. Rev. X vol. 4, 031003 (2014); L. K. Wagner, Phys. Rev. B vol. 92, 161116(R) (2015)
[4] B. W. Lebert, et al. Phys. Rev. B vol. 95 155110 (2017); B. Lebert et al., in preparation
[5] M. d'Astuto et al. Phys. Rev. B vol. 88, 014522 (2013); B. Lebert et al., arXiv:1904.08258, hal-02103389 (2019)
[6] M. K. Crawford, et al. Science vol. 250, 1390 (1990)
[7] J. Graf, et al. Phys. Rev. Lett. vol. 100, 227002 (2008)
[8] L. Chaix, et al. Nat Phys. vol. 13, 952 (2017).

Organizer: JASRI Diffraction and Scattering Division Tsutsui Satoshi
e-mail:satoshiatspring8.or.jp/PHS: 3479

Contact Address SPring-8 Seminar secretariat Shinobu Miyoshi / Minako Koujibata General Administration Division/ SPring-8/Japan Synchrotron Radiation Research Institute (JASRI)
Last modified 2019-11-11 13:05