PhD - Leuven | More than two weeks ago
Lattices determine the behavior of crystalline materials, and the ability to engineer lattices and super-lattices has been a topic of major interest for physicists, materials scientists and mathematicians alike. When lattices are combined or interfered, new superlattices and other emergent phenomena may appear. This is most prominent in two dimensions, where the interference of one- respectively two-dimensional lattices can give rise to the emergence of so-called moire-superlattices, either through the interference of optical laser beams  or interplay between the respective atomic 2D lattices at the interface between two two-dimensional semiconductors [2,3].
The effect of moire-superlattices on the behavior of particles trapped in them (atoms, for the optical versions; or electrons, for the physical interface based ones) can be profound: high-Tc superconductivity  and a plethora of highly correlated electron phases  have been observed recently in moire superlattices based on heterostructure interfaces of respectively graphene and two-dimensional transition metal dichalcogenides (TMDs). Yet, most of these studies have been based on (unproven) assumptions of infinitely stiff lattices without any interactions, which is inconsistent with recent experimental observations [2,3]. Therefore, the true effect of interfacial moire patterns on transport properties of two-dimensional materials remains very much a prominent research direction.
In this PhD research, you will investigate the respective methods of creating moire patterns, and the interaction between optical and interfacial moire patterns in TMDs – where the latter can be interpreted as dielectric engineering, one of the unique features of two-dimensional materials. You will need to delve deeply into the exact nature of the interface between two-dimensional materials, and how these dielectric superlattices interact with optical superlattices that are either commensurate or incommensurate with them. You will develop spectroscopic methods to investigate the effect of these superlattices on the emergent electronic behavior of TMD heterostructures. Your mission, should you decide to accept it, will be to create true understanding of the roles of interfaces and moire patterns on TMDs. You will interact closely with a variety of top research groups both inside imec and outside, with expertises ranging from advanced growth, patterning and transfer of TMDs, advanced patterning and structuring of light, low-dimensional and quantum transport, and advanced spectroscopy and metrology. From the outset, this PhD topic will be both theoretical and experimental, approximately 50% each.
 D. Kouznetsov, Q. Zheng, P. Van Dorpe and N. Verellen, PRL 125, 184101 (2020)
 A. Sushko*, K. De Greve*, T. Andersen, G. Scuri et al., arxiv 1912.07446 (2019)
 T. Andersen*, G. Scuri*, A. Suhko*, K. De Greve* et al., Nat. Mat. 20, 480 (2021)
 Y. Cao, V. Fatemi, S. Fang, K. Watanabe et al., Nature 556, 43 (2018)
 Y. Xu, S. Liu, D. Rhodes, K. Watanabe et al., Nature 587, 214 (2020)
Required background: physics, photonics, materials science, engineering
Type of work: 50% experiment, 50% theory
Supervisor: Kristiaan Degreve
Co-supervisor: Niels Verellen
Daily advisor: Steven Brems
The reference code for this position is 2022-014. Mention this reference code on your application form.