Guangze Chen,¹ Malte Rösner,² Jose L. Lado³

¹Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Gothenburg, Sweden
²Institute for Molecules and Materials, Radboud University, NL-6525 AJ Nijmegen, The Netherlands
³Department of Applied Physics, Aalto University, 02150 Espoo, Finland

Quantum spin liquids (QSL) are exotic phases of matter featuring strong entanglement and fractional excitations [1]. They have attracted much research interest due to their potential Majorana physics and relation to high-temperature superconductivity. Despite the discovery of material candidates for QSL in magnetic van der Waals materials such as 1T-TaS₂ [2], 1T-TaSe₂ and α-RuCl₃, it remains a remarkable challenge to (i) find stable QSL regimes and (ii) identify the QSL phase in these materials.
To overcome these challenges, we propose impurity, twist, and substrate engineering of magnetic van der Waals materials as a means of realizing and identifying QSL. Focusing on the material candidate 1T-TaS₂, we first show that a magnetic impurity can induce spinon zero modes in the potential Dirac QSL state in this material. We show that such spinon zero modes can be probed with scanning tunneling microscopy (STM), which enables the characterization of the Dirac QSL state [3]. Second, we show that a twisted bilayer 1T-TaS₂ hosts Moire spinons, whose bandstructure can be modified by encapsulating the twisted bilayer with ferromagnets such as CrI₃. We show that, applying a magnetic field on this heterostructure can tune the spinon bandstructure, which is a signature of the Dirac QSL state in 1T-TaS₂ [4]. Finally, we show that by placing 1T-TaS₂ on substrates with different dielectric constants, the Coulomb interaction between electrons in 1T-TaS₂ can be modified due to different electric screenings. We show that this results in a screening-dependent effective Heisenberg model, which can be engineered toward the QSL regime [5]. Our results put forward new strategies to engineer and probe QSL in magnetic van der Waals materials.

References:
[1] L. Savary and L. Balents, Reports on Progress in Physics 80, 016502 (2016).
[2] K. T. Law and P. A. Lee, PNAS 114, 6996 (2017).
[3] G. Chen and J. L. Lado, Phys. Rev. Research 2 033466 (2020).
[4] G. Chen and J. L. Lado, Phys. Rev. Research 3, 033276 (2021).
[5] G. Chen, M. Rösner and J. L. Lado, J. Phys.: Condens. Matter 34, 48 (2022).