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

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

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

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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