ComEPT · Combining Electrons and Phonons in Twisted materials
Horizon 2020 — Marie Skłodowska-Curie Actions
- Duration
- 2021-05-01 → 2023-04-30
- EU contribution
- €212,934
- Participants
- 1
- Scheme
- MSCA-IF
Lines connect the coordinator with its partners.
Results in brief
Combining Electrons and Phonons in Twisted materials
If one places a regularly ruled transparent plastic sheet on top of another identical plastic sheet and then rotates the top sheet while holding the bottom one fixed, a beautiful moiré pattern emerges. Since 2018, experimentalists have been able to create similar moiré patterns with atomically thin two-dimensional (2D) materials, such as graphene or transition-metal dichalcogenides (TMDs), with precisely controlled rotation or twist angles between the layers. These novel moiré materials exhibit many fascinating electronic, vibrational, and optical properties that are all tunable through the twist angle, such as flat electronic bands, moiré phonons, and excitons. This has generated tremendous excitement and given rise to the new field of twistronics. One of the striking features of the moiré materials is the emergence of intriguing phenomena that are not present in individual layers and its tunability with twist angle and doping. Despite significant progress in experiments in this field, the computation of electronic and optical properties based on accurate first-principles calculations remains highly challenging. This has hindered atomistic understanding of how electrons and phonons couple with each other to create exotic electronic and excitonic transport. The major challenge in performing first-principles calculations is that they are computationally much more demanding as the unit cells of the moiré superlattices often contain several thousands of atoms. In this project, we address the key challenge of developing and employing new and computationally efficient first-principles-derived atomistic methods to facilitate accurate computation and to provide key insights into the exotic electronic, vibrational, and optical properties of moiré materials. Overall objectives: We set out to achieve three Research Objectives (ROs). • RO1: Investigate emergent phonons and electron-phonon coupling mediated phenomena in moiré materials using a combination of first principles and forcefields based simulations. • RO2: Atomistic modelling of moiré excitons • RO3: Investigate role of atomic relaxations in formation of flat electronic bands in several moiré materials relevant to experimentalists using first-principles methods.
Data: CORDIS, © European Union
Project objective
The recent discovery of correlated insulating states and unconventional superconductivity in twisted bilayer graphene triggered an intense research effort to understand the properties of moiré materials. The ability to manipulate electronic properties through the twist angle between two two-dimensional materials has given rise to the new field of twistronics. Besides novel electronic properties, moiré materials also feature unconventional vibrational properties, such as novel phason modes. The ability to control vibrations by twisting gives rise to the new field of twistnonics.Despite much progress, many experimental observations in moiré materials are not yet well understood. For example, the microscopic origin of the “strange” metal phase with a resistivity which is linear in temperature and the nature of pairing glue that induces superconductivity are hotly debated. To answer these questions, I propose to combine the fields of twistronics and twistnonics and study the role of electron-phonon interactions in twisted bilayer materials. Specifically, I plan to+ develop a computational framework to study electron-phonon interactions in moiré materials. Because of the large unit cells of moiré materials, standard implementations of this approach cannot be used. To overcome this challenge, I will combine force-field approaches for phonons with tight-binding methods for electrons and develop a new parallelized computer code.+ understand electron transport experiments in different twisted bilayer materials, including twisted bilayer transition metal dichalcogenides and twisted bilayer graphene. + study the electron-phonon mediated superconductivity in twisted bilayer materials. The results of these calculations will enable a detailed understanding of the interactions between electrons and phonons in moiré materials and enable the control of exotic quantum phenomena with the twist angles.
Original text from CORDIS.
Participants
- IMPERIAL COLLEGE OF SCIENCE TECHNOLOGY AND MEDICINE · LondonCoordinatorUnited Kingdom
Links
Data: CORDIS, © European Union