Atomic-scale imaging of a static and dynamic ordered electronic state pinned by lattice defects

• Applicant: Dr. Michael Kinyanjui
• Subject Area: Experimental Condensed Matter Physics ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: from 2020 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 452020359

How are the strain state, topological phase defects, and glass–like properties of a sheet of electrons influenced by defects in the underlying atomic lattice? What are the atomic-scale properties of these topological defects and glassy states? What influence do topological phase defects and disorder have on dynamical properties in an applied electric field? These are some of the unclear issues observed when charge density waves – an ordered electronic ground state characterized by a periodic charge density and atomic position modulation – are pinned by defects in the underlying atomic lattice.The goal of the proposed project is to provide an atomic scale understanding of the interaction between a static CDW – without applied electric field – with the underlying lattice disorder. This is in addition to the first atomic-scale visualization of disorder-pinning of a dynamic CDW – under an applied electric field. The proposed project will adopt the following approach: (I) Use free-standing single layers with well defined CDW state (II) Induce and characterize lattice defects in these layers through electron-beam irradiation (III) Directly image and characterize static and dynamic CDW strain, topological defects formation, and order-disorder transitions as response to pinning by lattice defects and applied electric field. This will be done by simultaneous electron-irradiation, atomic-scale imaging and spectroscopy, as well as in-situ electrical biasing for CDW dynamics in the transmission electron microscope (TEM). The results of this project are expected to contribute towards understanding the atomic-scale effect of lattice disorder on a macroscopic electronic ordered state, its dynamics, associated phase transitions, and rational defect design in quantum materials.

• DFG Programme: Research Grants