Advisor(s)

Ilias Perakis
David Hilton

Committee Member(s)

Cheng-Chien Chen
Julia Chan
Kannatassen Appavoo
Renato Camata

Document Type

Dissertation

Date of Award

1-27-2026

Degree Name

Doctor of Philosophy (PhD)

School

College of Arts and Sciences

Department

Physics

Abstract

We report on terahertz time-domain spectroscopy measurements of iron selenide thin films of various thicknesses grown on a magnesium oxide substrate, focusing on the frequency-dependent complex conductivity in the range of 0.25 - 7 THz. By an- alyzing films with and without an approximately 100 nm thick Se capping layer, we examined the role of oxidation in the suppression of superconductivity. X-ray photo- electron spectroscopy data confirmed that oxidation was effectively mitigated, yet the films exhibited insulating behavior down to 200 mK, a temperature range that has not been extensively studied in this system. Our results indicate that the suppression of superconductivity in these FeSe thin films is independent of oxidation and is likely influenced by other factors such as structural strain and interfacial effects. This work provides new insights into the behavior of FeSe in the low-temperature regime and suggests potential pathways for tuning superconductivity through structural modifi- cations. Further exploration of light-matter interactions, quantum fluctuations, and low-temperature magnetic ordering in this material may offer a deeper understanding of its electronic properties and potential applications in quantum technologies.

Keywords

Iron selenide;Low temperature;Oxidation;Superconducivity;Terahertz spectroscopy;Ultrafast

ProQuest Publication Number

32173737

ISBN

9798273387492

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