Nano Letters 24, 14615 (2024)
Controlling excitons and their transport in two-dimensional (2D) transition metal dichalcogenide heterostructures is central to advancing photonics and electronics on-chip integration. We investigate the controlled generation and manipulation of excitons and their complexes in monolayer MoSe₂−WSe₂ lateral heterostructures (LHSs). Incorporating graphene as a back gate and edge contact in a field-effect transistor geometry, we achieve the precise electrical tuning of exciton complexes and their transfer across interfaces. Photoluminescence and photocurrent maps at 4 K reveal the synergistic effect of the local electric field and interface phenomena in the modulation of excitons, trions, and free carriers. We observe spatial variations in the exciton and trion densities driven by exciton−trion conversion under electrical manipulation. Additionally, we demonstrate controlled narrow-band emissions within the LHS through carrier injection and electrical biasing. Density functional theory calculation reveals significant band modification at the lateral interfaces. This work advances exciton manipulation in LHS and shows promise for next-generation 2D quantum devices.

Once again, the Wissenschaftsnacht at RWTH Aachen proved to be a resounding success! This year, as in previous years, many members of our group contributed their time and expertise to make the evening a memorable experience for visitors.

On Monday 04.11.2024, Eike Icking successfully defended his PhD thesis. Congratulations to Dr. Eike Icking on this great accomplishment! Note the fantastic cake by Corinne Steiner.

On 27.09.2024, Samuel Möller successfully defended his PhD thesis. Congratulations to Dr. Samuel Möller on this commendable accomplishment!

Today we celebrated that Emma Horgan from Imperial College London successfully completed her 12-week internship in our group as part of the ML4Q Undergraduate Research Internship Program. During her internship, Emma actively participated in our research activities related to bilayer graphene quantum dots and made valuable contributions to our ongoing projects. We greatly appreciate Emma's enthusiasm and the fresh perspectives she has brought to our team. We wish her all the best!

Last Friday, our annual institute excursion to the Wildenhof at the Rursee took place once again, and it was a great fun! The day kicked off with cycling (for a few of us) and various water sport activities in the morning. In the afternoon, we gathered on the terrace for a barbecue, with plenty of food and drinks to go around. A big thank you to everyone who participated and helped make this happen!

Nano Letters 24, 11454 (2024)
Cryogenic field-effect transistors (FETs) offer great potential for applications, the most notable example being classical control electronics for quantum information processors. For the latter, on-chip FETs with low power consumption are crucial. This requires operating voltages in the millivolt range, which are only achievable in devices with ultrasteep subthreshold slopes. However, in conventional cryogenic metal-oxide-semiconductor (MOS)FETs based on bulk material, the experimentally achieved inverse subthreshold slopes saturate around a few mV/dec due to disorder and charged defects at the MOS interface. FETs based on two-dimensional materials offer a promising alternative. Here, we show that FETs based on Bernal stacked bilayer graphene encapsulated in hexagonal boron nitride and graphite gates exhibit inverse subthreshold slopes of down to 250 μV/dec at 0.1 K, approaching the Boltzmann limit. This result indicates an effective suppression of band tailing in van der Waals heterostructures without bulk interfaces, leading to superior device performance at cryogenic temperature.

We are pleased to announce that Professor Slava Rotkin from Penn State University (US) has successfully completed a 3 month visit to our group. During this time, Slava worked closely with our team, contributing to several ongoing projects and sharing valuable insights from his extensive expertise in nanoscience and nanotechnology, with a particular focus on theoretical modelling of nanomaterials. We wish Slava continued success in his future endeavours and hope that this sabbatical experience has been as rewarding for him as it has been for our group.