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:2026/colloquium-with-kartik-ay@8F96275E-9F55-4B3F-A143-836282E12573 CREATED:20260419T191244 LOCATION: SUMMARY:Colloquium with Kartik Ayyer and Ermes Peci X-ALT-DESC;FMTTYPE=text/html:

Colloquium with Kartik Ayyer (Max Plank Institute - Hamburg) and Ermes Peci (VU Amsterdam)< /p>

12:30 - 12:50 Ermes Peci, Postdoc, PhotoConversion Mat erials, VU Amsterdam

Titel: Semicondu cting 2D materials: who they are and what they do

Abstr act: What happens to a semiconductor when it is only three a toms thick? This question has driven the growing interest in 2D trans ition metal dichalcogenides (TMDCs) over the past decade. These atomi cally thin semiconductors exhibit many remarkable physical phenomena, including tightly bound excitons that dominate their optical respons e, layer-dependent bandgaps, strong light-matter interactions, and co upled spin and valley physics. Understanding these effects is crucial not only for fundamental science but also for enabling next-generati on optoelectronic devices. In this talk, I will begin with an overvie w of the electronic and optical properties that make 2D TMDCs so dist inctive. I will then discuss how these three‑atom‑thick crystals can be fabricated and  what can be learned by characterizing the m with optical techniques, including less commonly used spectroscopic methods such as ellipsometry. Finally, I will present ongoing work o n photothermal effects in hybrid systems composed of plasmonic nanopa rticles and 2D semiconductors.


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

Titel:  Serial diffractive imaging to study nanoscale structural dynamics

Abstract: X-ray free electron lasers provide a unique opportunity to measure ultrafast, high resolution dynamics u sing diffractive imaging methods. In particular, I will focus on meas urements on ensembles of nanosystems where the high peak brightness e nables a serial (one-at-a-time) imaging approach which, when combined with modern machine learning analysis algorithms, provides much rich er information than conventional ensemble measurements. Building upon our 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 nanosyste ms, (i) large polaron formation in CsPbBr3 quantum dots [3], (ii) deh ydration dynamics on MS2 bacteriophage capsids using deep learning [4 ,5] and (iii) plasmon-induced structural deformations of gold nanorod s. Finally, I will discuss the possibility of using such an approach to observe ultrafast dynamics where precise optical triggering 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 a l. arXiv:2407.11687 (2024).
5. Zhuang et al. IUCrJ 9(2), 204-214 ( 2022).

DESCRIPTION: 12:30 - 12:50 Ermes Peci, Postdoc, PhotoConversio n Materials, VU Amsterdam Titel: Semiconduc ting 2D materials: who they are and what they do Abstract: What happens to a semiconductor when it is only three atoms th ick? This question has driven the growing interest in 2D transition m etal dichalcogenides (TMDCs) over the past decade. These atomically t hin semiconductors exhibit many remarkable physical phenomena, includ ing tightly bound excitons that dominate their optical response, laye r-dependent bandgaps, strong light-matter interactions, and coupled s pin and valley physics. Understanding these effects is crucial not on ly for fundamental science but also for enabling next-generation opto electronic devices. In this talk, I will begin with an overview of th e electronic and optical properties that make 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 method s such as ellipsometry. Finally, I will present ongoing work on photo thermal effects in hybrid systems composed of 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:  Serial diffract ive imaging to study nanoscale structural dynamics Abstract: X-ray free electron lasers provide a unique opportunity to m easure ultrafast, high resolution dynamics using diffractive imaging methods. In particular, I will focus on measurements on ensembles of nanosystems where the high peak brightness enables a serial (one-at-a -time) imaging approach which, when combined with modern machine lear ning analysis algorithms, provides much richer information than conve ntional ensemble measurements. Building upon our proof-of-concept stu dies understanding the structural landscape of gold nanoparticles [1, 2], I will talk about three problems where we use this method to obs erve hitherto unseen properties of nanosystems, (i) large polaron for mation in CsPbBr3 quantum dots [3], (ii) dehydration dynamics on MS2 bacteriophage capsids using deep learning [4,5] and (iii) plasmon-ind uced structural deformations of gold nanorods. Finally, I will discus s the possibility of using such an approach to observe ultrafast dyna mics where precise optical triggering is not possible.

Referen ces:
1. Ayyer, et al. Optica, 8(1), 15-23 (2021).
2. Shen, et a l. 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). Colloquium with Ka rtik Ayyer (Max Plank Institute - Hamburg) and Ermes Peci (VU Amster dam) END:VEVENT END:VCALENDAR