Kurzfassung: Tw o-dimensional (2D)\, van der Waals crystals allow the creation of arbitrar y\, atomically precise heterostructures simply by stacking disparate monol ayers without the constraints of covalent bonding or epitaxy. Charge and e nergy transfer processes at these novel junctions is an area of burgeoning interest both from the fundamental and application points of view. At a t ype II heterojunction between two 2D semiconductors\, ultrafast charge tra nsfer has been previously determined to occur on the order of 10’s of fe mtoseconds after photoexcitation. However\, the coupling between the latti ce degrees of freedom of the photoexcited monolayers remains less understo od. We use ultrafast electron diffraction to directly visualize lattice dy namics in the individual monolayers of the van der Waals heterojunction. W e can track the transfer of energy from one layer to another by following the change in intensity of the Bragg peaks after photoexcitation. We disco ver that under photoexcitation\, thermal transport occurs at a rate a few orders of magnitude faster than what is explained by vibrational coupling alone\, which we quantify by launching phonons across the junction through sub- bandgap excitation. With the aid of first principles calculations\, we can shed light on the role of lattice dynamics during ultrafast electro nic processes at 2D van der Waals heterojunctions.
Biograp hie: Archana Raja completed her PhD in Chemical Physics from Col umbia University. After spending a year as a postdoc in the Applied Physic s department at Stanford University\, she joined the Kavli Energy and Nano science Institute at UC Berkeley. In July 2019\, she became a Staff Scient ist at the Imaging and Manipulation of Nanostructures Facility at the Mole cular Foundry and was awarded the Early Career Lab Directed Research and D evelopment Award. She is also the recipient of the Blanche R. and David K asindorf Fellowship in Physical Chemistry at Columbia University and the I nstitute Silver Medal at the Indian Institute of Technology in Bombay.
Get-Together: Im Anschluss an das Kolloquium (ca. 1 8 Uhr) sind Studentinnen und Mitarbeiterinnen eingeladen zu einem online G et-Together mit Dr. Archana Raja. Im einem Zoom Meeting gibt es die Gelege nheit\, mit der Referentin ins Gespräch zu kommen und sich über weibli che Perspektiven auf Herausforderungen in Studium und Berufsleben auszutau schen.
The colloquium will be followed by a Get-Together with Dr. Archana Raja in Zoom (about 6 p.m.). Female students and staff are invited to talk to the speaker and discuss female perspectives on challenges in s tudies and professional life.
DTSTAMP:20260624T181026Z CREATED:20220114T230626Z LAST-MODIFIED:20220117T230711Z END:VEVENT END:VCALENDAR