Ultrafast quasiparticle dynamics in the correlated semimetal Ca3Ru2 O7

Yakun Yuan, Peter Kissin, Danilo Puggioni, Kevin Cremin, Shiming Lei, Yu Wang, Zhiqiang Mao, James M. Rondinelli, Richard D. Averitt, Venkatraman Gopalan

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Abstract

The correlated polar semimetal Ca3Ru2O7 exhibits a rich phase diagram including two magnetic transitions (TN=56 K and TC=48 K) with the appearance of an insulating-like pseudogap (at TC). In addition, there is a crossover back to metallic behavior at T∗=30 K, the origin of which is still under debate. We utilized ultrafast optical-pump optical-probe spectroscopy to investigate quasiparticle dynamics as a function of temperature in this enigmatic quantum material. We identify two dynamical processes, both of which are influenced by the onset of the pseudogap. This includes electron-phonon relaxation and, below TC, the onset of a phonon bottleneck hindering the relaxation of quasiparticles across the pseudogap. We introduce a gap-modified twoerature model to describe the temperature dependence of electron-phonon thermalization, and use the Rothwarf-Taylor to model the phonon bottleneck. In conjunction with density functional theory, our experimental results synergistically reveal the origin of the T-dependent pseudogap. Further, our data and analysis indicate that T∗ emerges as a natural consequence of T-dependent gapping out of carriers, and does not correspond to a separate electronic transition. Our results highlight the value of low-fluence ultrafast optics as a sensitive probe of low-energy electronic structure, thermodynamic parameters, and transport properties of Ruddlesden-Popper ruthenates.

Original languageEnglish (US)
Article number155111
JournalPhysical Review B
Volume99
Issue number15
DOIs
StatePublished - Apr 4 2019

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All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

Cite this

Yuan, Y., Kissin, P., Puggioni, D., Cremin, K., Lei, S., Wang, Y., Mao, Z., Rondinelli, J. M., Averitt, R. D., & Gopalan, V. (2019). Ultrafast quasiparticle dynamics in the correlated semimetal Ca3Ru2 O7. Physical Review B, 99(15), [155111]. https://doi.org/10.1103/PhysRevB.99.155111