BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Vrije Universiteit Amsterdam//NONSGML v1.0//EN NAME:Colloquium with Kartik Ayyer and Ermes Peci METHOD:PUBLISH BEGIN:VEVENT DTSTART:20260305T123000 DTEND:20260305T141500 DTSTAMP:20260305T123000 UID:colloquium-with-kartik-ayyer-a@8F96275E-9F55-4B3F-A143-836282E12573 CREATED:20260825T120702 LOCATION: SUMMARY:Colloquium with Kartik Ayyer and Ermes Peci X-ALT-DESC;FMTTYPE=text/html:

Colloquium with Kart ik Ayyer (Max Plank Institute - Hamburg) and Ermes Peci (VU Amst erdam)

12:30 - 12:50 Ermes Peci, Postdoc, PhotoCon version Materials, VU Amsterdam

Titel : Semiconducting 2D materials: who they are and what they do

Abstract: What happens to a semiconductor when it is o nly three atoms thick? This question has driven the growing interest in 2D transition metal dichalcogenides (TMDCs) over the past decade. These atomically thin semiconductors exhibit many remarkable physical phenomena, including tightly bound excitons that dominate their opti cal response, layer-dependent bandgaps, strong light-matter interacti ons, and coupled spin and valley physics. Understanding these effects is crucial not only for fundamental science but also for enabling ne xt-generation optoelectronic devices. In this talk, I will begin with an overview of the electronic and optical properties that make 2D TM DCs so distinctive. I will then discuss how these three‑atom‑thic k crystals can be fabricated and  what can be learned by charact erizing them with optical techniques, including less commonly used sp ectroscopic methods such as ellipsometry. Finally, I will present ong oing work on photothermal effects in hybrid systems composed of plasm onic nanoparticles and 2D semiconductors.


12:50 -13 :45 Kartik Ayyer, Group Leader, Max Plank Institute for the Structure and Dynamics of Matter, Hamburg 

Titel:& nbsp; Serial diffractive imaging to study nanoscale structur al dynamics

Abstract: X-ray free electron lase rs provide a unique opportunity to measure ultrafast, high resolution dynamics using diffractive imaging methods. In particular, I will fo cus on measurements on ensembles of nanosystems where the high peak b rightness enables a serial (one-at-a-time) imaging approach which, wh en combined with modern machine learning analysis algorithms, provide s much richer information than conventional ensemble measurements. Bu ilding upon our proof-of-concept studies understanding the structural landscape of gold nanoparticles [1, 2], I will talk about three prob lems where we use this method to observe hitherto unseen properties o f nanosystems, (i) large polaron formation in CsPbBr3 quantum dots [3 ], (ii) dehydration dynamics on MS2 bacteriophage capsids using deep learning [4,5] and (iii) plasmon-induced structural deformations of g old nanorods. Finally, I will discuss the possibility of using such a n approach to observe ultrafast dynamics where precise optical trigge ring is not possible.

References:
1. Ayyer, et al. Optica, 8(1), 15-23 (2021).
2. Shen, et al. ACS Nano, 18, 24, 15576-15589 (2024).
3. Shen, et al. ACS Nano 19, 31, 28372-28382 (2025).
4. Mall, et al. arXiv:2407.11687 (2024).
5. Zhuang et al. IUCrJ 9(2) , 204-214 (2022).

DESCRIPTION: Colloquium with Kartik Ayyer (Max Plank Institute - Hambu rg) and Ermes Peci (VU Amsterdam) 12:30 - 12:50 Ermes Pe ci, Postdoc, PhotoConversion Materials, VU Amsterdam Titel: Semiconducting 2D materials: who they are and what th ey doAbstract: What happens to a semiconductor when it is only three atoms thick? This question has driven the growing in terest in 2D transition metal dichalcogenides (TMDCs) over the past d ecade. These atomically thin semiconductors exhibit many remarkable p hysical phenomena, including tightly bound excitons that dominate the ir optical response, layer-dependent bandgaps, strong light-matter in teractions, and coupled spin and valley physics. Understanding these effects is crucial not only for fundamental science but also for enab ling next-generation optoelectronic devices. In this talk, I will beg in with an overview of the electronic and optical properties that mak e 2D TMDCs so distinctive. I will then discuss how these three‑atom ‑thick crystals can be fabricated and  what can be learned by characterizing them with optical techniques, including less commonly used spectroscopic methods such as ellipsometry. Finally, I will pres ent ongoing work on photothermal effects in hybrid systems composed o f plasmonic nanoparticles and 2D semiconductors.
12:50 -13 :45 Kartik Ayyer, Group Leader, Max Plank Institute for the Structure and Dynamics of Matter, Hamburg Titel:  < /strong>Serial diffractive imaging to study nanoscale structural dyna micsAbstract: X-ray free electron lasers provide a u nique opportunity to measure ultrafast, high resolution dynamics usin g diffractive imaging methods. In particular, I will focus on measure ments on ensembles of nanosystems where the high peak brightness enab les a serial (one-at-a-time) imaging approach which, when combined wi th modern machine learning analysis algorithms, provides much richer information than conventional ensemble measurements. Building upon ou r proof-of-concept studies understanding the structural landscape of gold nanoparticles [1, 2], I will talk about three problems where we use this method to observe hitherto unseen properties of nanosystems, (i) large polaron formation in CsPbBr3 quantum dots [3], (ii) dehydr ation dynamics on MS2 bacteriophage capsids using deep learning [4,5] and (iii) plasmon-induced structural deformations of gold nanorods. Finally, I will discuss the possibility of using such an approach to observe ultrafast dynamics where precise optical triggering is not po ssible.

References:
1. Ayyer, et al. Optica, 8(1), 15-23 (2 021).
2. Shen, et al. ACS Nano, 18, 24, 15576-15589 (2024).
3. Shen, et al. ACS Nano 19, 31, 28372-28382 (2025).
4. Mall, et al. arXiv:2407.11687 (2024).
5. Zhuang et al. IUCrJ 9(2), 204-214 (202 2). END:VEVENT END:VCALENDAR