Dr Tom Siday MPhys, PhD, MInstP

• Fulford Junior Research Fellow, Somerville College, Oxford
• PhD in Electronic and Electrical Engineering, University College London
• MPhs in Physics, University of York

Dr Tom Siday received a Master of Physics degree from the University of York (2015) and completed his PhD in Electronic & Electrical Engineering at University College London (2020). His PhD thesis focused on boosting the sensitivity of near-field microscopes through the development of perfectly absorbing terahertz detectors and resonant antenna probes.

After his PhD, Tom spent 3 years (2019-2022) as a Postdoctoral Researcher at the University of Regensburg, Germany. After this he returned to the UK as a Postdoctoral Researcher at the University of Oxford (2023-2024). During this period, Tom was also awarded a Fulford Junior Research Fellowship at Somerville College. In these postdoctoral positions, he spent time developing new ways to access ultrafast dynamics on nanometre and atomic length scales and applied these techniques to a range of material systems: from two-dimensional semiconductors to light-harvesting materials.

• Physics Laboratory 2

Over his career, Tom's research interests have spanned everything from probing fundamental quantum dynamics in materials to developing new and practical ways to measure terahertz (10¹² Hz) light.

Currently, his work primarily focuses on developing bespoke techniques for ultrafast microscopy, to probe how quantum processes in materials play out in real time and real space:

Nanoscale and atomic ultrafast probes

Using sharp metal tips, it is possible to confine short pulses of light down to a few tens of nanometres using evanescent near fields. Combined with techniques like atomic force microscopy, these confined fields form the core of a powerful ultrafast nanoscope.

To reach the atomic scale, we can exploit nonlinearities hidden deep within the near fields of a nanoscope, such as the quantum tunnelling of electrons. This gives direct access to the length scale of a few atoms with femtosecond time resolution.

Microscale spectroscopy

While atomic- and nanoscale probes provide very fundamental and direct answers about light-matter interaction, the emergent properties of quantum materials are often more apparent across slightly larger length scales (~1-100 µm) – especially when the energy scale of collective excitations is in the terahertz range. To access these length scales, a small aperture can be used instead of a tip to efficiently collect evanescent near fields.

Ultrafast dynamics in two-dimensional quantum materials

The elusive quantum states of matter hosted by two-dimensional van der Waals materials – especially when stacked and twisted to form moiré superlattices –provides an extensive platform for investigating unconventional quantum processes. Yet, measuring the dynamical processes which govern these peculiar properties in many cases can only be access with ultrafast microscopy techniques. Tip-based nanoscopes can directly access the intrinsic length scale of moiré superlattices (≲ 10 nm), and aperture microscopes provide probably the only route to directly sampling the dynamics of tiny (~10 µm) scale samples over ultrafast timescales.

Developing terahertz technologies

The sensitive measurement of electromagnetic fields is at the core of all microscopies. Hence, Tom has invested significant time into improving the sensitivity and efficiency of these methods. In particular, he developed a metasurface design which can perfectly absorb light. This allowed for a dramatic improvement in efficiency as well as shrinking detector dimensions down to the nanoscale. He has also developed new ways to resonantly enhance the efficiency of tip-based nanoscopes.