Seminars

12 May 2026, 08:45 → 13 May 2026, 19:00 Asia/Nicosia

Amphitheater LRC019 (Library "Stelios Ioannou" - University of Cyprus )

Fotios Ptochos (University of Cyprus (CY))

Zoom link: https://cern.zoom.us/j/69174155423?pwd=rRTMWHw525NUFn517VzPBecOpkLt83.1 
or
meeting id: 691 7415 5423
password: 892837

Tuesday 12 May

09:45 → 10:45 Artificial quantum materials made of perovskite oxide heterostructures

Speaker: Dr Marios Hadjimichael
Affiliation: Department of Physics, University of Warwick, UK

Abstract
Perovskite oxide compounds, with the chemical formula ABO₃, exhibit a wide range of physical phenomena, including magnetism, ferroelectricity, colossal magnetoresistance, and superconductivity. Their simple structure enables the fabrication of artificial heterostructures using advanced deposition techniques, allowing distinct properties to be combined within a single system. Interactions between multiple degrees of freedom at interfaces can give rise to behaviour absent in the bulk constituents, providing a versatile platform for engineering quantum materials with novel functionalities through strain and interface design [1]. High-quality thin-film growth further enables access to regimes typically requiring extreme conditions in bulk materials, such as superconductivity in nickelates previously observed only under high pressure [2], complex polarization textures in ferroelectrics [3-5], and unconventional switching behaviour in strain-engineered incipient ferroelectrics [6].

In this talk, I will present an overview of my research on the design and fabrication of epitaxial oxide heterostructures with tailored quantum properties, together with their characterization using advanced experimental techniques. As illustrative examples, I will discuss recent investigations of nanoscale domain walls in ferroelectric superlattices using synchrotron diffuse X-ray scattering, which reveal their internal structure and depolarization-driven polarization rotation, in excellent agreement with theory [7]. I will also highlight recent progress in high-resolution, high-throughput real-space imaging of domain textures, and the insights these methods provide into the structure and dynamics of ferroelectric and ferroelastic domain walls [8].

Finally, I will turn to nickelate systems, motivated by the discovery of superconductivity in hole-doped infinite-layer films (RNiO₂, where R is a rare-earth cation). I will describe our work on electron doping of perovskite nickelates (RNiO₃) via A-site substitution in high-quality thin films [9], and discuss how the synthesis of near-ideal samples provides insight into the mechanisms underlying this emerging class of superconductors [10].

References
[1] P. Zubko et al., Annu. Rev. Condens. Matter Phys. 2, 141-165 (2011)
[2] E. Ko et al., Nature 638, 935-940 (2025)
[3] M. Hadjimichael et al., Nat. Mater. 20, 495-502 (2021)
[4] Zubko et al., Nature 534, 524-528 (2016)
[5] M. Hadjimichael et al., Phys. Rev. Mater. 4, 094415 (2020)
[6] L. Bastogne, L. Korosec et al., arXiv:2603.27590 (2026)
[7] E. Zatterin, P. Ondrejkovic, L. Bastogne et al., Phys. Rev. X. 14, 041052 (2024)
[8] W. Peng et al., Adv. Mater. 38, e15762 (2026)
[9] M. Hadjimichael et al., Adv. Electron. Mater. 9, 2201182 (2023)
[10] Z. Dong, M. Hadjimichael et al., Nano Lett. 25, 1233-1241 (2025)

10:45 → 11:45 Deciphering quantum materials with ultrafast microscopy on atomic length scales

Speaker: Dr Iaroslav Gerasimenko
Affiliation: Department of Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, Germany

Abstract
Ultrafast phenomena have opened up an emergent avenue of research in which short pulses of light are used to tune the properties of quantum materials on demand and to create new states of matter out of equilibrium, allowing their functional properties to be manipulated at high speed. Understanding the microscopic mechanisms underlying these ultrafast transformations requires the study of quantum materials at their intrinsic – angstrom-femtosecond-meV – length, time and energy scales.

In this talk, I will show how this ambitious goal can be achieved with our recent developments in THz-driven scanning tunnelling and near-field microscopies. I will show imaging and controlling a spectrum of a phonon-driven single-vacancy quantum emitter faster than its vibration period [1]. I will further present a fundamentally new microscopy approach that exploits extreme nonlinearities within tip-confined near-fields to bring all-optical microscopy to the atomic scale while retaining temporal information about light [2]. I will demonstrate how we use these techniques to elucidate the ultrafast nanoscale dynamics leading to the formation of novel metastable quantum states [3] and access quantum light-matter interaction at atomic scale.

References
[1] C. Roelcke et al., Nat. Photon. 18, 595–602 (2024).
[2] T. Siday et al., Nature 629, 329–334 (2024), F. Schiegl et al., Nano Lett. 26, 1689–1696 (2026).
[3] Y. Gerasimenko et al., Nat. Mater. 18, 1078–1083 (2019); J. Maklar et al., Sci. Adv. 9, eadi4661 (2023).

11:45 → 12:00 Break

12:00 → 13:15 Meetings with the Committee

13:15 → 14:30 Lunch break

14:30 → 15:30 Thermal and Thermoelectric Transport in Molecular and 2D Nanodevices

Speaker: Dr Charalambos Evangeli
Affiliation: Department of Materials, University of Oxford, UK
                    Department of Physics, Lancaster University, UK
                    Department of Physics, Universidad Autonoma de Madrid, Spain

Abstract
As electronic devices approach the atomic limit, performance is increasingly governed by quantum transport phenomena. Operating such devices necessitates high electrical currents while requiring efficient heat dissipation to avoid breakdown. This seminar explores these fundamental boundaries across two different platforms: single-molecule junctions and two-dimensional (2D) materials.

First, I will discuss the development of novel experimental techniques based on modified Scanning Tunneling Microscopy (STM) and High-Vacuum Scanning Thermal Microscopy (SThM), specifically designed for probing thermal and thermoelectric properties at the nanoscale.[1,2]

I will then present key results from these platforms, beginning with how quantum interference can be exploited to tune thermoelectric efficiency at the single-molecule level.[1,3] Transitioning to 2D systems, I probe the interplay between heat and charge transport in graphene devices under high current densities.[4,5] I will discuss how geometry and substrate-graphene interfaces define the operational limits of these devices, and demonstrate that by engineering these parameters, we can manipulate local thermoelectricity, Peltier and Joule heating.[6,7] These results show that controlling the temperature distributions at the nanoscale offers a way for on-chip thermal management.

References
[1] C. Evangeli, K. Gillemot, E. Leary, et al., Nano Lett. 2013, 13, 2141.
[2] A. Harzheim, C. Evangeli, et al., 2D Mater, 2020, 7, 041004.
[3] C. Evangeli, M. Matt, L. Rincon-Garcia, et al., Nano Lett. 2015, 15, 1006.
[4] C. Evangeli, S. Tewari, et al., Proceedings of the National Academy of Sciences 2022, 119 (27), e2119015119.
[5] C. Evangeli, E. McCann, et al., Carbon, 2021 178, 632-639
[6] A. Harzheim, J. Spiece, C. Evangeli, et al., Nano Lett. 2018, 18, 7719.
[7] C. Evangeli, J. Swett, J. Spiece, et al., ACS nano 2024 18 (17), 11153-11164.

15:30 → 16:30 Light-Matter Interactions in Confined Systems: Linear and Nonlinear Phenomena

Speaker: Dr Kyriacos Georgiou
Affiliation: Department of Physics, University of Cyprus, Cyprus

Abstract
Confined photonic systems provide a powerful platform for enhancing light-matter interactions, enabling access to a rich range of emergent optical and quantum phenomena. In this talk, the regimes of weak and strong coupling will be introduced, and the formation of hybrid light-matter states known as exciton-polaritons will be discussed. The role of these hybrid states in providing new routes to control the photophysical functionalities of molecular materials will be demonstrated. In particular, it will be highlighted how strong coupling enables new regimes of energy delocalization and interaction, including long-range polariton-assisted energy transfer and the emergence of collective nonlinear effects such as polariton condensation at room temperature.

Building on these concepts, it will be discussed how confined light-matter systems offer a versatile platform to engineer polariton-driven behaviour under ambient conditions. Finally, a research, teaching, and mentoring vision will be outlined, focused on developing a program that connects fundamental light-matter physics with applications in sustainable photonic and quantum technologies.

16:30 → 17:00 Break

17:00 → 18:15 Meetings with the Committee

Wednesday 13 May

09:00 → 10:00 2D Heterostructures for Low-Power, Atomically Thin Photonic Functionality

Speaker: Dr Charalambos Louca
Affiliation: NanoPhotonics Center, Cavendish Laboratory, University of Cambridge, UK

Abstract
Achieving strong optical nonlinearities and low-power photonic functionality requires materials in which light-matter interactions can be engineered down to the nanoscale. Atomically thin two-dimensional (2D) semiconductors, such as transition-metal dichalcogenides (TMDs), provide a uniquely powerful platform for this. Their tightly bound excitons and large oscillator strengths enable spin-valley control and provide access to sharp optical transitions in a cost-effective materials system. When assembled into van der Waals heterostructures, these layers can be combined and twisted without lattice-matching constraints, allowing excitonic and polaritonic states with optical properties not available in any individual material.

In this talk, I will first present work on MoS₂ bilayers demonstrating that interlayer tunnelling can align exciton dipoles out of plane, leading to a more than tenfold enhancement in polariton nonlinearity when strongly coupled to optical microcavities compared to monolayers. I will then show that the same bilayer microcavity architecture enables sub-picosecond, low-energy optical switching via a transition between light-matter coupling regimes. Finally, I will discuss ongoing work on plasmonic nanoparticle-on-mirror nanocavities, where extreme mode confinement compresses light to the length scale of the active material, opening distinct nonlinear regimes in self-assembled nanocrystal monolayers.

I will conclude by presenting an independent research programme at UCY centred on exciton engineering in hybrid and TMD/TMD heterostructures, strong light-matter coupling and ultrafast switching in optical cavities, along with a future sensing direction enabled by 2D polariton nonlinearities.

10:00 → 11:00 Ultrafast Action Spectroscopy: Watching Optoelectronic Devices at Work

Speaker: Dr Marios Maimaris
Affiliation: UltraFast Spectroscopy Group, Department of Physics, Politechnico Di Milano, Italy

Abstract
Modern technologies rely on optoelectronic devices whose macroscopic function—whether expressed as photocurrent, light emission, or optical wavefront control—emerges from microscopic photophysical processes. Many of these processes, including exciton localization, charge transfer, and free-carrier generation, unfold on ultrafast timescales, and their understanding is critical for improving device performance and enabling new applications. While conventional ultrafast optical spectroscopies have been invaluable in probing such dynamics, they typically investigate pristine materials rather than working devices, thus their signals are not necessarily directly linked to function and lack functional selectivity.

In this seminar, I will show how ultrafast action spectroscopy addresses this challenge by moving beyond passive probing toward active interrogation of optoelectronic devices under operating conditions, where photoinduced perturbations are used to modulate and probe device performance directly. I will first focus on organic optoelectronic devices, particularly organic solar cells, where photocurrent- and photoluminescence-based detection reveals ultrafast bound exciton formation and shows that hot-exciton can dissociate before acquiring bound character, thereby facilitating free-carrier generation. I will then discuss the current limitations of the approach and introduce a next-generation multidimensional ultrafast action spectroscopy platform under development for ultrafast spectrotemporal interrogation of optoelectronic devices. Extending this perspective from electrical to optical device output, I then turn to flat optical devices based on monolayer transition metal dichalcogenides. There, I investigate a metalens under operation and demonstrate ultrafast modulation of its focusing response, together with transient chiroptical and nonlinear optical effects pointing toward dynamically reconfigurable metasurfaces. Finally, I will outline future directions for applying ultrafast action spectroscopy across these systems and beyond.

11:00 → 11:15 Break

11:15 → 12:15 Towards practically relevant quantum technologies: from fundamental limits to real-world systems

Speaker: Dr Mariella Minder
Affiliation: School of Electrical Engineering, Cyprus University of Technology, Cyprus

Abstract
Quantum technologies promise unprecedented capabilities in secure communications, distributed quantum information processing, and networked quantum systems. Realising these capabilities in practice requires overcoming key limitations in distance, speed, and scalability across multiple experimental platforms. This talk presents an experimental research trajectory addressing these bottlenecks across quantum communications, computing, and networking. From the demonstration of the first effective quantum repeater, operating beyond conventional quantum key distribution (QKD) limits, to the development of a quantum computer expected to overcome the entangling gate speed limit of trapped-ion systems, and finally to the real-world deployment of operational QKD links and networks. Together, these advances illustrate how overcoming both fundamental and practical constraints can move quantum technologies from proof-of-principle experiments toward real-world implementation, while motivating future research on scalable architectures and enabling platforms for practically relevant quantum systems.

12:15 → 12:30 Break

12:30 → 13:00 Meetings with the Committee

13:00 → 14:15 Lunch break

14:15 → 15:30 Meetings with the Committee

15:30 → 18:30 Closed session of the committee members