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Superconductivity in Graphene Hetero-Structures: From Fundamental Physics to Functional Devices

Citation

Arora, Harpreet Singh (2020) Superconductivity in Graphene Hetero-Structures: From Fundamental Physics to Functional Devices. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/nc05-gr15. https://resolver.caltech.edu/CaltechTHESIS:06052020-175219708

Abstract

While graphene has been dubbed as a "wonder material" because of its amazing characteristics, such as the ability to conduct electricity better than copper and being two hundred times stronger than steel, until recently, the key quantum phenomenon of superconductivity was missing from the list of properties exhibited by graphene. In 2018, an astonishing discovery showed that by placing two sheets of graphene on top of each other in a structure known as Twisted Bilayer Graphene, it is possible to realize superconductivity when the rotation angle between the sheets is close to the "Magic Angle" value of 1.1°. More surprisingly, superconductivity in the initial reports was observed in close proximity to insulating states - resembling the phase diagram of High Tc superconductors. This sparked a fierce debate about its origin and its possible relation to High Tc superconductors. In this thesis, we show that by carefully engineering the dielectric environment of TBG, it is possible to stabilize superconductivity in non-magic angle TBG devices without the presence of any insulating states. This discovery imposes severe constraints on the origin of superconductivity in TBG. We also report, for the first time, the successful induction of spin-orbit coupling in TBG and discuss its implications.

Superconductivity can also be induced into graphene via coupling to conventional superconductors, and the strength of the induced supercurrent depends strongly on temperature. We employ this thermal dependence by integrating graphene into superconducting circuits that serves two purposes a) to investigate graphene's thermal behavior at milliKelvin temperatures and b) to utilize its extremely low heat capacity in making functional devices that have the potential to achieve ultra-high thermal sensitivity.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Twisted bilayer graphene, graphene, superconductivity, microwave circuits, correlated electronic systems, spin-orbit coupling
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Applied Physics
Thesis Availability:Withheld
Research Advisor(s):
  • Nadj-Perge, Stevan
Thesis Committee:
  • Roukes, Michael Lee (chair)
  • Rosenbaum, Thomas F.
  • Hsieh, David
  • Nadj-Perge, Stevan
Defense Date:4 June 2020
Funders:
Funding AgencyGrant Number
NSFCAREER DMR-1753306
GIST-Caltech Collaborative Research UNSPECIFIED
Record Number:CaltechTHESIS:06052020-175219708
Persistent URL:https://resolver.caltech.edu/CaltechTHESIS:06052020-175219708
DOI:10.7907/nc05-gr15
Related URLs:
URLURL TypeDescription
https://arxiv.org/abs/2002.03003arXivFirst author paper accepted in Nature, material from paper used in Chapter 3, 4, 6 and Appendices.
https://doi.org/10.1038/s41567-019-0606-5DOICo-authored paper, material from paper used in Chapter 2.
ORCID:
AuthorORCID
Arora, Harpreet Singh0000-0002-7674-735X
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13781
Collection:CaltechTHESIS
Deposited By: Harpreet Singh Arora
Deposited On:08 Jun 2020 22:31
Last Modified:23 Jun 2020 22:18

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