Application of Ultrafast Spectroscopy Techniques to Probe Correlated Ion Hopping Mechanisms in Solid-State Ion Conductors

Citation

Pham, Kim Hoang (2025) Application of Ultrafast Spectroscopy Techniques to Probe Correlated Ion Hopping Mechanisms in Solid-State Ion Conductors. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/825x-r459. https://resolver.caltech.edu/CaltechTHESIS:05222025-165729471

Abstract

Superionic conductors, or solid-state ion conductors that surpass the ionic con- ductivity of its liquid counterpart, can enable more energy dense batteries, robust artificial ion pumps, and optimized fuel cells. The mechanisms enabling superionic conductivity still remain elusive, though many-body correlations between the mi- grating ions, lattice vibrational modes, and charge screening clouds have all been posited to greatly enhance ionic conduction. Most spectroscopic techniques cannot directly probe and validate the role of such correlations due to their inability to transiently resolve these ultrafast dynamics occurring at picosecond timescales. In this work, we develop an ultrafast technique that measures the time-resolved change in impedance while a light source ranging from UV to THz frequencies selectively excites an ion-coupled correlation. The technique is used to compare the relative changes in impedance of a solid-state Li⁺ conductor Li_0.5La_0.5TiO₃ (LLTO) before and after light excitation to elucidate the role of charge screening clouds, optical phonons, and acoustic phonons on ion migration. From our techniques, we deter- mine that electronic screening and rocking phonon-mode interactions significantly dominate the ion migration pathway of LLTO compared to acoustic phonons. Al- though we only present one case study, our technique can extend to O²⁻, H⁺, or other charge carrier transport phenomena where ultrafast correlations control transport. Furthermore, the temporal relaxation of the measured impedance can distinguish ion transport effects caused by many-body correlations, optical heating, correlation, and memory behavior.

Item Type:

Thesis (Dissertation (Ph.D.))

Subject Keywords:

ultrafast spectroscopy, solid-state ionic conduction, correlated ion-hopping, lattice dynamics

Degree Grantor:

California Institute of Technology

Division:

Chemistry and Chemical Engineering

Major Option:

Chemistry

Thesis Availability:

Not set

Research Advisor(s):

Cushing, Scott K. (co-advisor)
See, Kimberly A. (co-advisor)

Thesis Committee:

Blake, Geoffrey A. (chair)
Stoltz, Brian M.
Faber, Katherine T.
See, Kimberly
Cushing, Scott K.

Defense Date:

18 November 2024

Funders:

Funding Agency	Grant Number
National Science Foundation Graduate Research Fellowship	UNSPECIFIED
Air Force Office of Science & Research	FA9550- 21-1-0022
U.S. Army DEVCOM ARL Army Research Office (ARO) Energy Sciences Competency, Advanced Energy Materials Program	W911NF-23-1-0001
DURIP	FA9550-23-1-0197
Research Corporation for Science Advancement	CS-CSA-2022-068
David and Lucile Packard Foundation	UNSPECIFIED

Record Number:

CaltechTHESIS:05222025-165729471

Persistent URL:

https://resolver.caltech.edu/CaltechTHESIS:05222025-165729471

DOI:

10.7907/825x-r459

Related URLs:

URL	URL Type	Description
https://doi.org/10.1063/5.0182323	DOI	Article adapted for Chapter 2
https://doi.org/10.48550/arXiv.2504.07249	arXiv	Article adapted for Chapter 3.
https://doi.org/10.48550/arXiv.2305.01632	arXiv	Article adapted for Chapter 4

ORCID:

Author	ORCID
Pham, Kim Hoang	0000-0003-4053-6363

Default Usage Policy:

No commercial reproduction, distribution, display or performance rights in this work are provided.

ID Code:

17264

Collection:

CaltechTHESIS

Deposited By:

Kim Pham

Deposited On:

23 May 2025 19:55

Last Modified:

23 May 2025 19:55

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