Two-dimensional spin helix and magnon-induced singularity in twisted bilayer graphene

Yung-Yeh Chang^1*, Chen-Hsuan Hsu¹

¹Institute of Physics, Academia Sinica, Taipei, Taiwan

* Presenter:Yung-Yeh Chang, email:cdshjtr@gmail.com

Twisted bilayer graphene shows correlated behaviors in various regimes. Near the magic angle, the coexistence of itinerant and localized electrons resembles heavy-fermion compounds [1]. Applying an interlayer bias results in a correlated domain wall network [2]. In this work, we explore a system that describes this correlated network as a sliding Tomonaga-Luttinger liquid coupled to localized spins. We demonstrate the formation of a two-dimensional spin helix with enhanced helix ordering temperature due to inter-domain-wall correlations. We also identify magnon-induced singularity in scaling dimensions of operators, similar to phonon-induced singularity in various (quasi-)one-dimensional systems [2,3]. Finally, we discuss experimental signatures of the spin helix phase.

References:
[1] Zhi-Da Song and B. Andrei Bernevig, Phys. Rev. Lett. 129, 047601 (2022)
[2] Hao-Chien Wang and Chen-Hsuan Hsu, 2D Mater. 11, 035007 (2024).
[3] Chen-Hsuan Hsu, Nanoscale Horiz. 9, 1725 (2024).

*This work was financially supported by National Science and Technology Council (NSTC), Taiwan through Grant No. NSTC-112-2112-M-001-025-MY3. Y.-Y.C. acknowledges the financial support from The 2023 Postdoctoral Scholar Program of Academia Sinica, Taiwan.

Keywords: Twisted bilayer graphene, Sliding Tomonaga-Luttinger liquid, Spin helix, Heavy fermion, Domain wall network