by Alexander Lau, Timo Hyart, Carmine Autieri, Anffany Chen, and Dmitry I. Pikulin has been published in Phys. Rev. X 11, 031017
The recent discovery of unconventional superconductivity in a twisted pair of graphene sheets is a famous consequence of what is known as a flat energy band. In such bands, the kinetic energy of a material’s electrons becomes negligible and their mutual interactions dominate, which gives rise to enhanced correlation effects and exotic phases of matter. So far, the study of these intriguing phenomena has focused on two-dimensional materials due to the lack of realistic proposals for their three-dimensional counterparts. Now, in new article published in Physical Review X researchers from three groups at the International Research Agenda MagTop, Institute of Physics, Polish Academy of Sciences (A. Lau, T. Hyart, and C. Autieri), together with Microsoft Quantum and the University of British Columbia, present a viable approach to fill this gap to lift the study of flat-band physics into the third dimension.
In their theoretical study, they show how strain engineering can be used to generate quasi-flat 3D energy bands in materials known as nodal-line semimetals. They find that the required strain profile can be realized in an experimentally feasible way, for instance, by bending the sample, which allows for in-situ tuning of the emerging correlated phases and the transition temperatures. Moreover, they identify rhombohedral graphite and CaAgP materials as promising material candidates to realize their proposal.
Their setup not only represents a three-dimensional analog of the celebrated twisted bilayer graphene but opens the door to tunable correlated phases in 3D materials. Their findings are also relevant for metamaterials and cold atomic gases, where the ingredients required for their proposal can be artificially engineered.