Microscopic understanding of topological edge-state transport

Topological materials exhibit unique properties distinct from their trivial counterparts, stemming from the intricate topology of their band structures. One notable yet partially understood example is the existence of ‘protected’ one-dimensional edge states, particularly characteristic in two-dimensional or higher-order topological materials. These edge states carry electrical currents that reflect the material's topological properties, such as dissipationless transport [1] and chiral anomaly [2] observed in macroscopic transport experiments.

This project aims to develop a microscopic understanding of topological edge-state transport through a combination of experimental observation and theoretical modeling. Specifically, you will simulate the nonequilibrium steady state of topological matter by theory [3], and you will measure the electronic density of states by scanning tunneling microscopy [4]. Throughout the project, you will answer a series of fundamental questions: Where are the edge states located? How do they interact with other states and how can they be effectively isolated? How do the spectral features evolve with applied current and/or magnetic field? When does dissipationless transport break down? These inquiries drive the exploration towards a comprehensive understanding of topological edge-state transport.

The selected candidate will work with Dr. Jianfeng Ge at MPI CPfS, specializing in cryogenic STM and transport characterization, as well as with Dr. Tobias Meng at TU Dresden, an expert in topological condensed matter theory. Ideal candidates will have a strong background in solid-state physics and knowledge across a range of experimental methodologies.

[1] S. Wu, V. Fatemi, Q. D. Gibson, K. Watanabe, T. Taniguchi, R. J. Cava, P. Jarillo-Herrero
Observation of the quantum spin Hall effect up to 100 Kelvin in a monolayer crystal
Science 359, 76 (2018)
[2] J. Gooth, A. C. Niemann, T. Meng, A. G. Grushin, K. Landsteiner, B. Gotsmann, F. Menges, M. Schmidt, C. Shekhar, V. Süß, R. Hühne, B. Rellinghaus, C. Felser, B. Yan, K. Nielsch
Experimental signatures of the mixed axial–gravitational anomaly in the Weyl semimetal NbP
Nature 547, 324 (2017)
[3] S. S. Hegde, T. Ehmcke, and T. Meng
Edge-Selective Extremal Damping from Topological Heritage of Dissipative Chern Insulators
Physical Review Letters 131, 256601 (2023)
[4] S. Howard, L. Jiao, Z. Wang, N. Morali, R. Batabyal, P. Kumar-Nag, N. Avraham, H. Beidenkopf, P. Vir, E. Liu, C. Shekhar, C. Felser, T. Hughes, Vidya Madhavan
Evidence for one-dimensional chiral edge states in a magnetic Weyl semimetal Co3Sn2S2
Nature Communications 12, 4269 (2021)

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