Public Abstract

DE-SC0022947: Emergent Many-Body Ground States and Collective Excitations in Ultra-Clean Bilayer Graphene Heterostructures

Award Status: Active

Institution: The Pennsylvania State University, University Park, PA
UEI: NPM2J7MSCF61
DUNS: 003403953

Most Recent Award Date: 07/02/2024
Number of Support Periods: 3
PM: Cantoni, Claudia

Current Budget Period: 07/01/2024 - 06/30/2025
Current Project Period: 07/01/2022 - 06/30/2025
PI: Zhu, Jun

Supplement Budget Period: N/A

Public Abstract

Graphene heterostructures offer a promising material platform to explore interaction-driven phenomena and their collective excitations, the fundamental understanding and control of which may ultimately lead to new concepts of quantum technologies. The PI’s lab recently developed techniques to achieve very clean Bernal-stacked bilayer graphene devices and devised methods to obtain the spin wave dispersion of a quantum Hall magnet formed by strong electron-electron correlations. The proposed effort will leverage these latest advances to advance the fundamental knowledge of novel many-body states arising from the interplay of interaction and topology in the fractional quantum Hall regime of a 2D system. The objectives of the proposed research include: 1: To understand the nature and properties of several unconventional fractional quantum hall states occurring on the N=1 Landau level of bilayer graphene, which are suspected to be non-Abelian. Non-Abelian states are foundations of topological quantum computing. 2: Earlier experiments showed that the valley isospin in bilayer graphene behaves as an SU(2) pseudospin. This project will experimentally explore the formation of valley skyrmions, a topological pseudospin texture, in quantum Hall valley ferromagnets formed in bilayer graphene. 3. Non-local transport-based excitation and detection will be used to probe the low-energy collective excitations accompanying a plethora of broken-symmetry ground states at integer and fractional fillings. The information will be used to illuminate the nature of the ground state orders. These objectives will be achieved through a combination of advanced device fabrication and low-temperature transport measurements at magnetic fields up to 45 T by using in-house and capabilities available at the National High Magnetic Field Laboratory. The success of the proposed effort will produce significant experimental advances to elucidate a number of fascinating interaction phenomena in 2D, with potential far-reaching impact on the emerging quantum information science and technology.

Graphene heterostructures offer a promising material platform to explore interaction-driven phenomena and their collective excitations, the fundamental understanding and control of which may ultimately lead to new concepts of quantum technologies. The PI’s lab recently developed techniques to achieve very clean Bernal-stacked bilayer graphene devices and devised methods to obtain the spin wave dispersion of a quantum Hall magnet formed by strong electron-electron correlations. The proposed effort will leverage these latest advances to advance the fundamental knowledge of novel many-body states arising from the interplay of interaction and topology in the fractional quantum Hall regime of a 2D system. The objectives of the proposed research include:

1: To understand the nature and properties of several unconventional fractional quantum hall states occurring on the N=1 Landau level of bilayer graphene, which are suspected to be non-Abelian. Non-Abelian states are foundations of topological quantum computing.

2: Earlier experiments showed that the valley isospin in bilayer graphene behaves as an SU(2) pseudospin. This project will experimentally explore the formation of valley skyrmions, a topological pseudospin texture, in quantum Hall valley ferromagnets formed in bilayer graphene.

3. Non-local transport-based excitation and detection will be used to probe the low-energy collective excitations accompanying a plethora of broken-symmetry ground states at integer and fractional fillings. The information will be used to illuminate the nature of the ground state orders.

These objectives will be achieved through a combination of advanced device fabrication and low-temperature transport measurements at magnetic fields up to 45 T by using in-house and capabilities available at the National High Magnetic Field Laboratory. The success of the

proposed effort will produce significant experimental advances to elucidate a number of fascinating interaction phenomena in 2D, with

potential far-reaching impact on the emerging quantum information science and technology.