Hyperbolic Cooper-Pair Polaritons in Planar Graphene/Cuprate Plasmonic Cavities

Michael E Berkowitz; Brian S Y Kim; Guangxin Ni; Alexander S McLeod; Chiu Fan Bowen Lo; Zhiyuan Sun; Genda Gu; Kenji Watanabe; Takashi Taniguchi; Andrew J Millis; James C Hone; Michael M Fogler; Richard D Averitt; D N Basov

doi:10.1021/acs.nanolett.0c03684

Hyperbolic Cooper-Pair Polaritons in Planar Graphene/Cuprate Plasmonic Cavities

Nano Lett. 2021 Jan 13;21(1):308-316. doi: 10.1021/acs.nanolett.0c03684. Epub 2020 Dec 15.

Authors

Affiliations

¹ Department of Physics, Columbia University, New York, New York 10027, United States.
² Department of Mechanical Engineering, Columbia University, New York, New York 10027, United States.
³ Condensed Matter Physics and Material Science Department, Brookhaven National Laboratory, Upton, New York 11973, United States.
⁴ Research Center for Functional Materials, National Institute of Material Science, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan.
⁵ International Center for Materials Nanoarchitectonics, National Institute of Material Science, Namiki 1-1, Tsukaba, Ibaraki 305-0044, Japan.
⁶ Department of Physics, University of California San Diego, La Jolla, California 92093, United States.

PMID: 33320013
DOI: 10.1021/acs.nanolett.0c03684

Abstract

Hyperbolic Cooper-pair polaritons (HCP) in cuprate superconductors are of fundamental interest due to their potential for providing insights into the nature of unconventional superconductivity. Here, we critically assess an experimental approach using near-field imaging to probe HCP in Bi₂Sr₂CaCu₂O_8+x (Bi-2212) in the presence of graphene surface plasmon polaritons (SPP). Our simulations show that inherently weak HCP features in the near-field can be strongly enhanced when coupled to graphene SPP in layered graphene/hexagonal boron nitride (hBN)/Bi-2212 heterostructures. This enhancement arises from our multilayered structures effectively acting as plasmonic cavities capable of altering collective modes of a layered superconductor by modifying its electromagnetic environment. The degree of enhancement can be selectively controlled by tuning the insulating spacer thickness with atomic precision. Finally, we verify the expected renormalization of room-temperature graphene SPP using near-field infrared imaging. Our modeling, augmented with data, attests to the validity of our approach for probing HCP modes in cuprate superconductors.

Keywords: Cuprate superconductors; graphene; hyperbolic Cooper-pair polaritons; plasmonic cavities; scattering-type scanning near-field microscopy; van der Waals heterostructures.