Science Faculty

Seminar: "Chirality in Moiré systems"

Speaker

Professors Tobias Stauber and Guillermo Gómez Santos

Institution of Origin

Condensed Matter Physics Department

Date

15-10-2021

Time

12:00 h

Place

Online event, MS-TEAMS, "Department Seminars"

Description

Twisted bilayer graphene has attracted much attention due to its novel electronic properties that arise in the flat band regime at the magic angle [1] [2] After a brief
introduction, we will present our recent theoretical results on the inherent chirality of the system.

In particular, we will show that the Moiré structure of TBG leads to a paramagnetic response and chiral plasmons which are accommodated by a longitudinal magnetic moment [3] This unusual response also leads to an emergent magnetic texture when the system is driven out of equilibrium [4].

The real space chirality of twisted bilayer graphene can be characterized by a simple formula and we observe a sign change due to an emergent C [6] symmetry Surprisingly, this change occurs in the flat band regime and thus offers a new definition of the magic angle based on a macroscopic observable which is accessible in typical transport experiments [5]

We finally predict an unprecedented large local chirality for the plasmonic near field if the twist angle is slightly away from the magic angle Twisted bilayer graphene or other Moiré heterostructure should thus provide a novel platform for chiral cavities that might be even able to catalyze the reaction of new chiral molecules while conserving time reversal symmetry [6]

[1] Y. Cao , V. Fatemi , A. Demir, S. Fang , Spencer L. Tomarken, Jason Y. Luo , J. D. Sanchez Yamagishi , K. Watanabe , T. Taniguchi , E. Kaxiras , R. C. Ashoori & P. Jarillo Herrero , Nature 556 , 80 (2018)
[2] Y. Cao , V. Fatemi , S. Fang , K. Watanabe , T. Taniguchi , E. Kaxiras , and P. Jarillo Herrero, Nature 556 , 43 (2018)
[3] T. Stauber , T. Low , and G. Gómez Santos, Phys . Rev. Lett . 120 , 046801 (2018); Phys . Rev. B 98 , 195414 (2018)
[4] D. Bahamon , G. Gómez Santos, T.Stauber , Nanoscale 12 , 15383 (2020)
[5] T Stauber J González, and G Gómez Santos, Phys Rev B 102 081404 (2020)
[6] T. Stauber ., T. Low , and G. Gómez Santos, Nano Letters 20 , 8711 (2020)

Observations

To join the group of "Department Seminars" click here.