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Ultrafast Optical Control of Order Parameters in Quantum Materials


Ning, Honglie (2023) Ultrafast Optical Control of Order Parameters in Quantum Materials. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/yxa0-6884.


Developing protocols to realize quantum phases that are not accessible thermally and to manipulate material properties on demand is one of the central problems of modern condensed matter physics. Impulsive electromagnetic stimulus provides an extensive playground not only to exert desired control over the material macroscopic properties but also to optically detect the underlying microscopic mechanisms. Two indispensable components form the cornerstone to realize these goals: a meticulous comprehension of light-induced phenomena and a suitable and versatile platform.

Abundant photoinduced phenomena emerge upon light irradiation. A collective oscillation of order parameter can be launched and probed in the weak perturbation regime; further increasing light intensity can transiently modulate the free-energy landscape, inducing a suppression, enhancement, reversal, and switch of order parameters; in the strong non-perturbative excitation regime, the system can be driven nonlinearly with microscopic coupling parameters modified. Understanding these light driven emergent phenomena lays the foundation of optical control and novel functionalities.

Quantum materials, embodying a large portfolio of topological and strongly correlated compounds, afford an exceptional venue to realize optical control. Owing to the complex interplay between the charge, spin, orbital, and lattice degrees of freedom, a rich phase diagram can be generated with various phases that are selectively and independently accessible via optical perturbations. They hence offer a wealth of opportunities to not only improve our comprehension of the underlying physics but also develop the next generation of ultrafast technologies.

In Chapter I of this thesis, I will first cover a multitude of light-induced emergent phenomena in quantum materials under the framework of time-dependent Landau theory, Keldysh theory, and Floquet theory, and then introduce several canonical microscopic models to quantitatively rationalize the intra- and interactions between different degrees of freedom in quantum materials. As the necessary theoretical background is established, three main experimental techniques that have been extensively utilized in my research: time-resolved reflectivity and Kerr effect, time-resolved second harmonic generation rotational anisotropy, and coherent phonon spectroscopy will be introduced in Chapter II. In Chapter III, I will demonstrate that a light-induced topological phase transition can be engendered concomitant with an inverse-Peierls structural phase transition in elemental Te. In Chapter IV, I will describe signatures of ultrafast reversal of excitonic order in excitonic insulator candidate Ta2NiSe5 and substantiate a manipulation of the reversal as well as the Higgs mode with tailored light pulses. In Chapter V, a light-induced switch of spin-orbit-coupled quadrupolar order in multiband Mott insulator Ca2RuO4 will be introduced. In Chapter VI, a Keldysh tuning of nonlinear carrier excitation and Floquet bandwidth renormalization in strongly driven Ca2RuO4 will be covered.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Condensed matter physics, quantum materials, optical control
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Minor Option:Physics
Awards:France A. Córdova Graduate Student Fund, 2021.
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Hsieh, David
Thesis Committee:
  • Refael, Gil (chair)
  • Bernardi, Marco
  • Cushing, Scott K.
  • Hsieh, David
Defense Date:3 August 2022
Non-Caltech Author Email:ninghlhero (AT)
Funding AgencyGrant Number
Institute for Quantum Information (IQI)UNSPECIFIED
Defense Advanced Research Projects Agency (DARPA)UNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
Department of Defense (DOD)UNSPECIFIED
Record Number:CaltechTHESIS:08292022-044824279
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for Chapter 4 adapted for Chapter 6
Ning, Honglie0000-0003-4867-0751
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:15013
Deposited By: Honglie Ning
Deposited On:09 Sep 2022 01:06
Last Modified:16 Jun 2023 16:41

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