Retention of Enhanced and Induced Superconductivity at Ambient Pressure Through High-Pressure Quenching

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dc.contributor.advisorChu, Paul C. W.
dc.contributor.committeeMemberHosur, Pavan
dc.contributor.committeeMemberMeen, James K.
dc.contributor.committeeMemberRen, Zhifeng
dc.contributor.committeeMemberTing, Chin-Sen
dc.creatorBontke, Trevor
dc.creator.orcid0009-0006-4151-3816
dc.date.accessioned2024-01-27T01:48:53Z
dc.date.available2024-01-27T01:48:53Z
dc.date.createdDecember 2023
dc.date.issued2023-12
dc.date.updated2024-01-27T01:48:54Z
dc.description.abstractIn the past eight years impressively high superconducting critical temperatures (T<sub>c</sub>s) have been reported in numerous materials. Among these include instances of anomalously high T<sub>c</sub>s that approach, and in some contested reports, meet and exceed room temperature (RT), pushing the field to new heights. Unfortunately, achieving such impressive critical temperatures requires ultra-high external pressures, rendering them unviable for commercial use. Therefore, one of the most significant challenges remaining in the field of superconductivity is to retain the high T<sub>c</sub> phases induced by pressure while lowering or removing it completely. We have therefore employed a pressure quenching technique to retain high-pressure-induced/-enhanced superconducting phases in Bi, FeSe, and Cu<sub>x</sub>Fe<sub>1.01-x</sub>Se at ambient pressure. Pressure quenching bismuth at 77 K and 4.2 K from pressures up to 26.6 GPa successfully produced metastable superconducting phases with varying T<sub>c</sub>s from ∼ 5 K up to a new record of 9 K. By changing the pressure quenching parameters, different metastable phases could be targeted, namely Bi-III with a T<sub>c</sub> around 7 K and Bi-V with a T<sub>c</sub> > 8 K. Temporal stability testing and thermal cycling revealed a lower temperature limit below ∼ 60 K and an upper temperature limit of 120 K – 150 K in metastable bismuth. Pressure quenches performed on FeSe and Cu<sub>x</sub>Fe<sub>1.01-x</sub>Se near the superconducting dome resulted in metastable phases with maximum T<sub>c</sub>s of 37 K and 25 K, respectively. Thermal cycling of FeSe and Cu<sub>x</sub>Fe<sub>1.01-x</sub>Se showed a similar lower temperature limit for temperatures up to ∼ 120 K and an upper temperature limit around 175 K for Cu<sub>x</sub>Fe<sub>1.01-x</sub>Se. Annealing metastable FeSe to room temperature produced T<sub>c</sub>s from 15 K – 24 K. Notably, a non-superconducting hexagonal phase retained in FeSe was slowly annealed to room temperature for a few days resulting in a superconducting phase near the dome peak. Lastly, a temporal stability test of metastable Cu<sub>x</sub>Fe<sub>1.01-x</sub>Se was conducted which showed perfect phase stability for 7 days when kept below 50 K. Overall, these results demonstrate the potential this technique has in targeting desirable superconducting phases induced or enhanced by pressure and retaining them in a metastable state at ambient pressure.
dc.description.departmentPhysics, Department of
dc.format.digitalOriginborn digital
dc.format.mimetypeapplication/pdf
dc.identifier.citationPortions of this document appear in: L. Deng, T. Bontke, R. Dahal, Y. Xie, B. Gao, et al. Pressure-induced high-temperature superconductivity retained without pressure in FeSe single crystals. Proceedings of the National Academy of Sciences, 118(28), 2021.
dc.identifier.urihttps://hdl.handle.net/10657/16218
dc.language.isoeng
dc.rightsThe author of this work is the copyright owner. UH Libraries and the Texas Digital Library have their permission to store and provide access to this work. UH Libraries has secured permission to reproduce any and all previously published materials contained in the work. Further transmission, reproduction, or presentation of this work is prohibited except with permission of the author(s).
dc.subjectsuperconductivity
dc.subjectsuperconductor
dc.subjectFeSe
dc.subjectCuxFe1.01-xSe
dc.subjectBi
dc.subjectBismuth
dc.subjecthigh pressure,low temperature
dc.subjectpressure quench
dc.subjectcritical temperature
dc.subjectmetastable
dc.titleRetention of Enhanced and Induced Superconductivity at Ambient Pressure Through High-Pressure Quenching
dc.type.dcmitext
dc.type.genreThesis
thesis.degree.collegeCollege of Natural Sciences and Mathematics
thesis.degree.departmentPhysics, Department of
thesis.degree.disciplinePhysics
thesis.degree.grantorUniversity of Houston
thesis.degree.levelDoctoral
thesis.degree.nameDoctor of Philosophy

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