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Electrical excitation of a Van der Waals magnet
The goal of this semester project is to electrically excite excitons in atomically thin CrSBr and measure both the electrical and optical response at temperatures down to 4 K.
Two-dimensional semiconductors are some of the most promising materials for future optoelectronics and photonics. The strong Coulomb interaction and the quantum confinement lead to the formation of strongly bound electron-hole pairs, so called excitons. Recently, van der Waals magnets such as CrSBr gained attention due to the additional coupling of excitons with the magnetic order, while still strongly interacting with light [1,2]. However, most studies rely on optical excitation, whereas direct electrical access still remains a challenge.
The goal of this semester project is to electrically excite excitons in atomically thin CrSBr and measure both the electrical and optical response at temperatures down to 4 K. Therefore, you will first build tunnel junctions from metallic graphene and isolating hBN by exfoliation from bulk crystals. After electrically characterizing these structures you will add thin flakes of CrSBr on top in order to electrically generate excitons. The device is then mounted inside a closed-cycle cryostat and measured across the whole temperature range with focus on the Néel temperature at around 132 K. The project will combine optical spectroscopy with electrical measurements in a challenging cryogenic environment. Furthermore, you will gain insight into fabrication of van der Waals heterostructures by building and exfoliating your own devices. Finally, applying our knowledge of solid state physics and optics will allow us to gain more insight into these new and exotic atomically thin layers.
References:
[1] Wilson, N.P., Lee, K., Cenker, J. et al. Interlayer electronic coupling on demand in a 2D magnetic semiconductor. Nat. Mater. 20, 1657–1662 (2021).
[2] Dirnberger, F., Quan, J., Bushati, R. et al. Magneto-optics in a van der Waals magnet tuned by self-hybridized polaritons. Nature 620, 533–537 (2023).
[3] Wang, L., Papadopoulos, S., Iyikanat, F. et al. Exciton-assisted electron tunnelling in van der Waals heterostructures. Nat. Mater. 22, 1094–1099 (2023).
Two-dimensional semiconductors are some of the most promising materials for future optoelectronics and photonics. The strong Coulomb interaction and the quantum confinement lead to the formation of strongly bound electron-hole pairs, so called excitons. Recently, van der Waals magnets such as CrSBr gained attention due to the additional coupling of excitons with the magnetic order, while still strongly interacting with light [1,2]. However, most studies rely on optical excitation, whereas direct electrical access still remains a challenge. The goal of this semester project is to electrically excite excitons in atomically thin CrSBr and measure both the electrical and optical response at temperatures down to 4 K. Therefore, you will first build tunnel junctions from metallic graphene and isolating hBN by exfoliation from bulk crystals. After electrically characterizing these structures you will add thin flakes of CrSBr on top in order to electrically generate excitons. The device is then mounted inside a closed-cycle cryostat and measured across the whole temperature range with focus on the Néel temperature at around 132 K. The project will combine optical spectroscopy with electrical measurements in a challenging cryogenic environment. Furthermore, you will gain insight into fabrication of van der Waals heterostructures by building and exfoliating your own devices. Finally, applying our knowledge of solid state physics and optics will allow us to gain more insight into these new and exotic atomically thin layers.
References: [1] Wilson, N.P., Lee, K., Cenker, J. et al. Interlayer electronic coupling on demand in a 2D magnetic semiconductor. Nat. Mater. 20, 1657–1662 (2021). [2] Dirnberger, F., Quan, J., Bushati, R. et al. Magneto-optics in a van der Waals magnet tuned by self-hybridized polaritons. Nature 620, 533–537 (2023). [3] Wang, L., Papadopoulos, S., Iyikanat, F. et al. Exciton-assisted electron tunnelling in van der Waals heterostructures. Nat. Mater. 22, 1094–1099 (2023).