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


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.


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:Public (worldwide access)
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
Funding AgencyGrant Number
GIST-Caltech Collaborative ResearchUNSPECIFIED
Record Number:CaltechTHESIS:06052020-175219708
Persistent URL:
Related URLs:
URLURL TypeDescription author paper accepted in Nature, material from paper used in Chapter 3, 4, 6 and Appendices. paper, material from paper used in Chapter 2.
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
Deposited By: Harpreet Singh Arora
Deposited On:08 Jun 2020 22:31
Last Modified:06 Jul 2021 20:49

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