Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session Z65: Topological Superconductivity III
11:30 AM–2:18 PM,
Friday, March 18, 2022
Room: Hyatt Regency Hotel -Grant Park C
Chair: Fan Zhang, UT Dallas
Abstract: Z65.00011 : 1D supercurrent in a graphene heterostructure
1:54 PM–2:06 PM
Presenter:
Julien Barrier
(Univ of Manchester)
Authors:
Julien Barrier
(Univ of Manchester)
Alexey Berdyugin
(Manchester University(Indiana))
Piranavan Kumaravadivel
(Univ of Manchester)
Na Xin
(Univ of Manchester)
Jonathan R Prance
(Lancaster Univ)
Minsoo Kim
(Univ of Manchester)
Rashid Jalil
(UET Lahore)
Roshan Krishna Kumar
(Lancaster Univ)
Saurav Islam
(Indian Institute of Science Bangalore)
Takashi Taniguchi
(NIMS)
Kenji Watanabe
(NIMS)
A K Geim
(Univ of Manchester)
We propose that twisted bilayer graphene (tBLG) Josephson junctions can realize such topological excitations. When the twist angle is significantly smaller than 1°, the superlattice consists of large (~µm wide) triangular domains with alternating Bernal (AB/BA) stacking order. In this system the domain boundaries allow valley-polarised 1D helical states with four gapless 1D states on each side of the triangular domains, propagating in opposite directions for valley K and K’ [3,4].
In our Josephson junctions, the supercurrent persists deep into the quantum Hall regime, i.e. under magnetic fields breaking the time-reversal symmetry, ensuring s-wave pairing. We observe pockets of superconductivity in Landau levels at all magnetic fields below the critical field of the superconducting contacts, which we attribute to unconventional Andreev bound states propagating along 1D helical channels.
Our results show that tBLG is a particularly appealing system to engineer topological superconductivity. We provide evidence of the topological nature of the domain boundaries, a decisive step towards realizing exotic quasiparticles.
1. Alicea, J. Rep Prog Phys, 75, 076501 (2012)
2. Beenakker C. Annu Rev Conden Ma P 4, 113-136 (2013)
3. Huang, S. et al., Phys Rev Lett 121, 037702 (2018)
4. Xu, S. et al., Nat Commun 10, 1-5 (2019)
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