Public defence in Engineering Physics, M.Eng. Xin Huang
Public defence from the Aalto University School of Science, Department of Applied Physics.
When
Where
Event language(s)
In this event, we are committed to Aalto University’s principles for a safer space.
Title of the thesis: Different Is More---Selected Works in Heterostructures of Transition Metal Dichalcogenides
Doctoral student: Xin Huang
Opponent: Professor Teemu Ojanen, University of Tampere
Custos: Professor Adam Foster, Aalto University School of Science, Department of Applied Physics
Introducing two advances in lateral and vertical heterostructures and their new physics.
A heterostructure is a composite structure made of different components. When assembled together, the whole heterostructure exhibits new properties distinct from those of their individual constituents. Heterostructures provide a powerful platform for creating artificial designer quantum matter.
This research focuses on two-dimensional (2D) materials, particularly transition metal dichalcogenides (TMDCs). Using molecular beam epitaxy (MBE), we synthesized lateral heterostructures of VSe₂ and NbSe₂, as well as vertical heterostructures of 1T/1H-NbSe₂. We further studied their electronic properties using scanning tunneling microscopy (STM) and spectroscopy (STS).
In the work on VSe₂—NbSe₂ lateral heterostructures, our protocols successfully created atomically sharp 1D interfaces between these two single layers. We systematically studied their structural details and revealed an intriguing phenomenon: the emergence of Kondo resonance around the interfaces. This phenomenon arises from the interactions between localized magnetic moments in VSe₂ and conduction electrons from NbSe₂.
In the work on a 1T/1H-NbSe₂ vertical heterostructure, single-layer 1T-phase NbSe₂ was grown on top of 1H-phase NbSe₂. Charge transfer from the bottom layer to the top layer resulted in the formation of a doped Mott insulator—a starting point for studying high-temperature superconductors. We further analyzed the spatial distribution of the doped/undoped sites and uncovered possible charge correlations between them.
These results pave the way for producing and understanding many-body physics in strongly correlated systems. Together, these selected works highlight the potential of combining different structures to create more unknown phenomena and explore more novel physics.
Keywords: heterostructures, transition metal dichalcogenides, scanning tunneling microscopy
Thesis available for public display 10 days prior to the defence at: https://aaltodoc.aalto.fi/doc_public/eonly/riiputus/
Contact information: https://attopunk.xyz
Doctoral theses at the School of Science: https://aaltodoc.aalto.fi/handle/123456789/52