Strong pseudospin-lattice coupling in Sr3Ir2O7: Coherent phonon anomaly and negative thermal expansion

L. L. Hu, M. Yang, Y. L. Wu, Q. Wu, H. Zhao, F. Sun, W. Wang, Rui He, S. L. He, H. Zhang, R. J. Huang, L. F. Li, Y. G. Shi, and Jimin Zhao
Phys. Rev. B 99, 094307 – Published 19 March 2019

Abstract

The similarities to cuprates make iridates an interesting potential platform for investigating superconductivity. Equally attractive are their puzzling complex intrinsic interactions. Here, we report an ultrafast optical spectroscopy investigation of a coherent phonon mode in Sr3Ir2O7, a bilayer Ruddlesden-Popper perovskite iridate. An anomaly in the A1g optical phonon (ν=4.4THz) is unambiguously observed below the Néel temperature (TN), which we attribute to pseudospin-lattice coupling (PLC). Significantly, we find that PLC is the dominant interaction at low temperature, and we directly measure the PLC coefficient to be λ=150±20cm1, which is two orders of magnitude higher than that in manganites (<2.4cm1) and comparable to that in CuO (50cm1, the strongest PLC or spin-lattice coupling (SLC) previously known). Moreover, we find that the strong PLC induces an anisotropic negative thermal expansion. Our findings highlight the key role of PLC in iridates and uncovers another intriguing similarity to cuprates.

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  • Received 19 July 2018

DOI:https://doi.org/10.1103/PhysRevB.99.094307

©2019 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

L. L. Hu1, M. Yang1,6, Y. L. Wu1, Q. Wu1,6, H. Zhao1,6, F. Sun1,6, W. Wang2, Rui He3, S. L. He4, H. Zhang5, R. J. Huang2, L. F. Li2, Y. G. Shi1,6, and Jimin Zhao1,6,7,*

  • 1Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
  • 2Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China
  • 3Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409, USA
  • 4Ningbo Institute of Material Technology & Engineering, Chinese Academy of Sciences, Ningbo 315201, China
  • 5College of Physical Science and Technology, Sichuan University, Chengdu 610065, China
  • 6School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
  • 7Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China

  • *Corresponding author: jmzhao@iphy.ac.cn

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Issue

Vol. 99, Iss. 9 — 1 March 2019

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