March 2016

Abstracts of the QSIT Lunch Seminar, Thursday, March 3, 2016

Mapping an electron wave function by a local electron scattering probe

Christian Reichl, Advanced Semiconductor Quantum Materials, ETH Zurich

We've developed a technique which allows for the detailed mapping of the electronic wave function in two-dimensional electron gases with low-temperature mobilities up to 15 million cm2/Vs. Thin ("delta") layers of aluminium are placed into the 2DEG regions, causing electron scattering which depends very locally on the amplitude of the electron wave function at the position of the Al δ-layer. By changing the distance of this layer from the interface we map the shape of the wave function perpendicular to the interface. Despite having a profound effect on the electron mobiliy, the δ -layers do not cause a widening of the quantum Hall plateaus.

Fermi polaron-polaritons in MoSe

Meinrad Sidler, Quantum Photonics Group, ETH Zurich

Transition metal dichalcogenide (TMD) monolayers are a new family of atomically thin 2D semiconductors. They feature a unique band structure giving rise to a valley pseudospin and a non-zero Berry curvature at the band minimum. Their truly 2D nature as well as their large electron mass infer strong Coulomb interactions which imply strong exciton binding energies of order 500 meV. TMDs in photoluminescence also exhibit a strongly bound trion state red/shifted from the exciton line by 30meV. In this talk, I will present cavity spectroscopy of gate-tunable monolayer MoSe2 exhibiting strongly bound exciton-polaron and trion resonances, as well as non-perturbative coupling to a single microcavity.