Physics Colloquium

27.11.2017 5:15 p.m., room: T-1004
Dr. Helmut Schultheiss (Helmholtz-Zentrum Dresden-Rossendorf)
Magnon Transport in Spin Textures
11.12.2017 5:15 p.m., room: T-1004
Professor Rolf Haug (Universität Hannover)
Shot Noise in Single-Electron Tunneling through Quantum Dots: A Toolbox to Study Quantum Physics
8.1.2018 5:15 p.m., room: T-1004
Ursula Wurstbauer (Walter Schottky Institut, TU München)
Exzitonen, Phononen und Elektronen in van der Waals Heterostrukturen

Optically active, atomically thin semiconductors are an emergent class of two-dimensional materials. Particularly, monolayers of semiconducting transition metal dichalcogenides (SC-TMDs), such as MoS2, excel in their large optical response. The light-matter interaction in such monolayers is dominated by exciton phenomena, resulting in a layer- and energy-dependent extraordinarily high absorbance of more than 15% for a less than 1nm thick crystal [1,2]. The outstanding optical properties together with intriguing spin- and valley-properties, catalytic activity [3], photocatalytic stability [4] and anisotropic charge and heat transport renders possible manifold applications based on SC-TMD monolayers. Key to the integration of SC-TDM monolayers into opto-/electronic circuitries is the possibility to tune and engineer their properties on demand and on-chip e.g. by defects [5] and dielectric environment [6,7] or doping [1,8]. After an introduction to the properties of SC-TMDs, I will talk about the influence of the dielectric environment on the single particle band structure, charge carrier density as well as on excitonic properties [4,6,7] of those atomically thin crystals and discuss consequences for their integration into optoelectronic circuits [6]. Next, I introduce van der Waals heterostructures - a novel platform for tailored heterostructures without the limitations of lattice mismatch. These heterostructures host long-lived momentum direct and indirect interlayer excitons making those structures an interesting material system to study quantum phase transitions and many-body phenomena of composite bosons [9]. I will close the talk with prospective van der Waals hetero- and hybrid structures that hold great potential for energy conversion applications in the areas of photovoltaics, catalysis and thermoelectrics. The work is supported by the Deutsche Forschungsgemeinschaft (DFG) via excellence cluster Nanosystems Initiative Munich (NIM) as well as DFG projects WU 637/4-1 and HO3324/9-1.

[1] U. Wurstbauer, B. Miller, E. Parzinger, and A. W. Holleitner, J. Phys. D: Appl. Phys. 50, 173001 (2017).

[2] S. Funke, B. Miller, E. Parzinger, P. Thiesen, A. W. Holleitner, and U. Wurstbauer, J. Phys.: Condens. Matter 28, 385301 (2016).

[3] E. Parzinger, E. Mitterreiter, M. Stelzer, F. Kreupl, J. Ager, A. Holleitner, and U. Wurstbauer, Applied Materials Today, 8, 132-140 (2017).

[4] E. Parzinger, B. Miller, B. Blaschke, J. Garrido, J. Ager, A. Holleitner, and U. Wurstbauer, ACS Nano, 9 (11), 11302–11309 (2015).

[5] J. Klein, A. Kuc, A. Nolinder, M. Altzschner, J. Wierzbowski, F. Sigger, F. Kreupl, J.J. Finley, U. Wurstbauer, A. W. Holleitner, and M. Kaniber, 2D Materials 5, 011007 (2018).

[6] E. Parzinger, M. Hetzl, U. Wurstbauer, and A. Holleitner, npj 2D Materials and Applications, 2D Materials and Applications 1, 40 (2017).

[7] S. Diefenbach. E. Parzinger, J. Kiemle, J. Wierzbowski, S. Funke, B. Miller, R. Csiki, P. Thiesen, A. Cattani-Scholz, U. Wurstbauer, and A.W. Holleitner, submitted (2017).

[8] B. Miller, E. Parzinger, A. Vernickel, A. Holleitner, and U. Wurstbauer, Appl. Phys. Lett. 106, 122103 (2015).

[9] B. Miller, A. Steinhoff, B. Pano, F. Jahnke, A. Holleitner, and U. Wurstbauer, Nano Lett. 17(9), 5229–5237 (2017).

22.1.2018 5:15 p.m., room: T-1004
Prof. Dr. Paulo A. Maia Neto (Universidade Federal do Rio de Janeiro)
Using laser beams and colloids to probe the quantum vacuum