Seminar Speaker

Venue

B10A, Basement of Kane Science Building, UCC

4pm / Monday,  20th November, 2023

Title

How do giant planets form?

Protoplanetary discs surrounding young newborn stars consist of gas and to a small fraction of dust. These micro meter sized dust grains can then grow to become mm-cm sized pebbles, which drift inwards due to gas drag. The pebbles themselves can form planetesimals (10-100km sized objects), which can further grow by accreting the leftover pebbles. Once the planetary core grows to 10 Earth masses, it can attract a gaseous envelope and become a gas giant. This overall growth process is know as the core accretion scenario and it can reproduce the majority of the observed exoplanets. However, this scenario is now challenged by observation of the planetary atmospheres.  It is thought that the atmospheric composition of planets holds key to their formation location, where especially the C/H, O/H and C/O of the atmospheres are key ingredients, as these ratios vary with orbital distance from the star due to the evaporation of different oxygen and carbon bearing species like H2O, CO2, CH4 and CO. In this talk I will present a state-of-the-art model that allows tracking of the chemical components of the disc and inside of growing planets. I will first explain the ingredients of this model and then show its applications to the composition of forming planets and how this depends on the formation environment.

Seminar Speaker

Anthony Kiely, School of Physics, University College Dublin

B10A, Basement of Kane Science Building, UCC

4pm / Monday,  13th November, 2023

Title

First Passage Times for Continuous Quantum Measurement Currents

In undergraduate quantum mechanics, a measurement is an instantaneous destructive event, collapsing the wavefunction. It is also experimentally possible to perform a continuous quantum measurement.

This is done by performing a very ‘weak’ measurement again and again very quickly. This has the overall effect of minimally disturbing the system, while only obtaining a partial amount of information about it.

The first passage time is the time taken for a stochastic process to reach a certain threshold. In this talk, I will address the first passage time of the stochastic measurement current of continuously measured quantum systems. I will show how this can be described by deterministic linear differential equations rather than statistical inferences from many simulations of the random measurement outcomes. In the quantum jump unravelling this takes the form of a coupled system of master equations, while for quantum diffusion it becomes a type of quantum Fokker-Planck equation.

Seminar Speaker

B10A, Basement of Kane Science Building, UCC

4pm / Monday,  6th November, 2023

Title

Quantum materials at ultra-low temperatures:
quantum phase transitions and quantum oscillations.

Quantum phase transitions occur at the absolute zero of temperature, but strongly influence the properties of many materials over a wide region of their phase diagram. In some cases, quantum phase transitions lead to completely new phases of quantum matter, including unconventional superconducting and magnetic states, that are fundamentally very interesting and also potentially useful. However, we are not yet able to fully characterise, microscopically describe, or predict the development of these new quantum phases.

I will give a short introduction to quantum phase transitions, and then present some recent experimental work that exploits the behaviour of quantum oscillations to extract information about the microscopic properties of exotic quantum phases at ultra-low temperatures - as close as we can get to zero temperature phase transition.
Finally, I will explain how I plan to develop a deeper understanding of quantum phase transitions and their role in generating new quantum states, through ultra-low temperature experiments here at UCC.

Seminar Speaker

B10A, Basement of Kane Science Building, UCC

4pm / Monday,  23rd October, 2023

Title

Linking exoplanet diversity to their formation environment

More than 5000 exoplanets have been discovered to date. Their diverse physical and chemical properties present both a challenge for current planet formation models and also an opportunity to further our understanding of how planets form. To understand which factors and to what extent they determine the outcome of planet formation, we need to look into the environment in which planets form, which is the protoplanetary disc. Observations of discs with the Atacama Large Millimeter/submillimeter Array (ALMA) at high resolution show that substructures are ubiquitous and prevalent. Emission lines from volatile and refractory molecules in the disc were also identified. In the near future, the James Webb Space Telescope (JWST) will provide us with additional information of the disc composition very close to the star where planets form. Because disc substructures and composition are new parameters that have yet to be explored in detail, it is therefore important to continuously update our planet formation models so that these new parameters are taken into account. In this talk, I will introduce the field of planet formation focussing on the processes that occur in protoplanetary discs. This will be followed by a showcase of recent results from my work on understanding how physical processes in the disc influence the chemical composition.

Seminar Speaker

B10A, Basement of Kane Science Building, UCC

3.35pm / Monday,  9th October, 2023

Title

Atomic scale simulations of materials and devices for nanoelectronics applications

Field effect transistors (FETs) are the building blocks of integrated circuits (ICs) and are made of silicon (Si). Common components in most of these ICs are random-access memories, flash memories, processors, and application-specific circuits. There is ongoing interest in reducing the size of FETs, because smaller FETs allows higher FET density and consequently higher function per unit area at lower unit cost. In recent years, more and more fundamental changes are becoming necessary; e.g., introducing new materials and novel designs for the FETs. One class of new materials which have shown very promising properties is 2D materials. 2D materials possess unique properties such as inert surfaces and thickness-dependent electrical properties as well as ultimate body thickness, and sizable and tunable bandgap. As a result, they offer prospects of unprecedented advances in device performance at the atomic limit opening up opportunities for novel nanoelectronics device design.

Understanding the physics of carrier transport through these 2D materials is a fundamental and interesting question to investigate before they find their way into the IC manufacturing industry. In this seminar, I will explain the research activities we are currently carrying out in order to enhance our understanding of the fundamental properties of the 2D materials.