Project Details
Projekt
Non-equilibrium carrier dynamics in proximity-coupled graphene
Applicant
Professorin Dr. Isabella Gierz-Pehla
Subject Area
Experimental Condensed Matter Physics
Term
since 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 449119662
The interface between epitaxial graphene (EG) and SiC(0001) is a confined space that allows for the growth of novel two-dimensional materials (2DMs) with fascinating electronic properties including Mott insulators, Rashba materials, superconductors, and possibly topological insulators. While these 2DMs are interesting in their own right, they also offer an intriguing platform to investigate various proximity-induced effects on the graphene layer that rests on top of them. The main objective of the present project is to investigate the influence of the intercalated 2DM on the non-equilibrium carrier dynamics (NECD) of the graphene layer with time- and angle-resolved photoemission spectroscopy (tr-ARPES). Aside from the well-known equilibrium proximity-induced effects such as proximity-induced spin-orbit coupling and superconductivity, the NECD of EG will be influenced by additional non-equilibrium proximity-induced effects such as ultrafast charge transfer across the EG/2DM interface and photo-induced phase transitions.Before addressing these main objectives, we propose to use confinement epitaxy to stabilize honeycomb layers made of Bi, Sb, or Sn with topologically non-trivial electronic properties at the interface between EG and SiC(0001), and to obtain a better understanding of the influence of structural defects on the NECD of EG/SiC(0001). In detail, this project will address the following open questions:Can we stabilize honeycomb layers with topologically non-trivial electronic properties at the interface between EG and SiC(0001)?What is the influence of structural defects on the NECD of graphene? Does this influence change in the presence of a proximity-coupled 2DM?Is there ultrafast charge transfer between EG and the proximity-coupled 2DM?Can we control the NECD of various EG/2DM heterostructures via doping and screening?How are the NECD of graphene affected by the presence of a proximity-coupled topological insulator, Mott insulator, or superconductor?What is the influence of a possible photo-induced phase transition in the 2DM on the NECD of EG?In order to answer these questions, we will excite different EG/2DM heterostructures with wavelength-tunable visible, infrared, or mid-infrared femtosecond pump pulses and probe the NECD of the heterostructure as a function of energy, momentum, and time with tr-ARPES. For that purpose, an extreme ultraviolet probe pulse will eject photoelectrons from the sample. These photoelectrons will be dispersed according to their emission angle and kinetic energy with a hemispherical analyzer such that the photocurrent imaged on a two-dimensional detector will directly reveal a snapshot of the non-equilibrium carrier distribution within the band structure of the EG/2DM heterostructure. Varying the pump-probe delay will then allow us to record slow-motion movies of the NECD as well as possible photo-induced band structure changes.
DFG Programme
Research Units
