In correlated transition metal oxides (TMOs), interactions between the electron, lattice, spin and orbital degrees of freedom (DOFs) have proven to be a fertile land of emergent quantum phenomena and competing quantum phases.  The delicate balance between these competing quantum phases are often sensitive to standard external stimuli, including pressure, magnetic and electric field, offering avenues for new functionalities.  In the past decades, profound advancement of material science and ultrafast science opens up exciting possibilities for exploiting ultrafast laser spectroscopy to dynamically study and control competing phases in quantum materials with photons.  In this talk, I will describe state-of-the-art ultrafast spectroscopic technique that enabled us to access the photo-induced states in TMOs.  I will show examples that demonstrate ultrafast dynamic control of strongly correlated quantum materials by mode-selective excitation with pulsed electromagnetic field.  These include: (i) Cooperative photo-induced metastable “hidden” phase in a colossal magnetoresistance (CMR) manganite La_0.67Ca_0.33MnO₃, investigated by ultrafast far-field pump-probe spectroscopy and near-field scanning optical microscope. (ii) Recent experimental discovery of a new collective mode induced by optical excitation in a stripe-ordered cuprate superconductor La_2-xBa_xCuO₄, and evidenced by time-domain THz spectroscopy. I will discuss the future of ultrafast dynamic study and control of quantum materials using new strategies and spectroscopic technique.

Biosketch

Dr. Jingdi Zhang received his B.S. in Physics at University of Science and Technology of China in 2007 with Prof. Xianhui Chen, and then Ph.D. in Physics at Boston University in 2014 with Prof. Richard Averitt. He is now a postdoctoral researcher at Department of Physics, University of California San Diego with Prof. Richard Averitt and Prof. Dmitri Basov. His main research interest is the study of strongly correlated electron materials, metamaterials and plasmonics using ultrafast spectroscopy, infrared nano-imaging & nano-spectroscopy.