Ultrafast signatures of spin and orbital orders in the spin-orbit entangled Mott insulator Sr<sub>2</sub>CrO<sub>4</sub>

ORAL

Abstract

We used ultrafast optical spectroscopy to study non-equilibrium spin and orbital order dynamics in Sr2CrO4, a 3d antiferromagnetic Mott insulator. Sr2CrO4 possesses multiple collective phases exhibiting stripe-type orbital order (T < 50 K), Néel-type spin order (T < 113 K), and antiferro-type orbital order (T < 140 K), though the details of the antiferro-type orbital order are not fully understood. In our experiments, we varied the pump photon energy to selectively drive intersite spin hopping between neighboring Cr t2g orbitals and charge transfer-type transitions between oxygen 2p and Cr eg orbitals. This revealed temperature-dependent anomalies in the transient reflectivity at 1.55 eV across the Néel temperature at 113 K as well as 50 K and 140 K, which can be linked to spin and orbital order. Our results reveal the distinct relaxation timescales for spin and orbital orders, respectively, and provide experimental evidence for antiferro-type orbital ordering below 140 K.

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Presenters

  • Min-Cheol Lee

    • Los Alamos National Laboratory
    • Center for Integrated Nanotechnologies, Los Alamos National Laboratory

Authors

  • Min-Cheol Lee

    • Los Alamos National Laboratory
    • Center for Integrated Nanotechnologies, Los Alamos National Laboratory

  • Connor Occhialini

    • Department of Physics, Massachusetts Institute of Technology

  • Jiarui Li

    • Massachusetts Institute of Technology MIT
    • Department of Physics, Massachusetts Institute of Technology

  • Zhihai Zhu

    • Massachusetts Institute of Technology MIT
    • Department of Physics, Massachusetts Institute of Technology

  • La Moyne Mix

    • Los Alamos National Laboratory
    • CINT, Los Alamos National Lab

  • Dmitry Yarotski

    • Los Alamos National Laboratory
    • CINT, Los Alamos National Lab
    • Department of Physics, Massachusetts Institute of Technology
    • Center for Integrated Nanotechnologies, Los Alamos National Laboratory

  • Riccardo Comin

    • Massachusetts Institute of Technology MIT
    • Department of Physics, Massachusetts Institute of Technology

  • Rohit P Prasankumar

    • Los Alamos National Laboratory
    • CINT, Los Alamos National Lab
    • Center for Integrated Nanotechnologies, Los Alamos National Laboratory