ULtrafast Spectroscopy of Emergent Phenomena in nanomaterials
My research asks the question: how does structural arrangement and coupling of components in a material give rise to quantum optical properties that the individual parts do not possess? I study this emergence as it happens, using ultrafast spectroscopy to watch polarons form, coherences develop, energy cascade, and chirality transfer on femtosecond to picosecond timescales. Doing this matters because the emergent properties we uncover are the functional basis of technologies:
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A polaron is one of the reasons a structurally imperfect, solution-processed metal halide perovskite film can transport charge across microns without scattering & understanding how it forms enables principled design of next-generation light-harvesting and light-emitting devices.
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Chirality emerging at an organic-inorganic interface is a route to converting the handedness of a photon into a spin-polarized current without any magnetic field, enabling opto-spintronic switches and spin-selective logic that operate at optical speeds.
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Directed energy flow across a structurally engineered nanoarchitecture is the physical principle behind low-dissipation energy routing in molecular-scale circuits and quantum batteries where energy must be channeled to a specific site.
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Coherences we observe developing and decaying in real time - quantum superpositions of excitonic and vibrational states - are the same resource that quantum sensing & quantum information processing seek to harness and protect.
Designing these technologies require understanding the whole - the coupled system, interface, arrangement - and they require catching the emergence of function.
Below are some snapshots of our work:
Ultrafast Quasiparticle Dynamics
Quasiparticless such as polarons, self-trapped excitons and coherent phonon wavepackets are emergent: they do not exist in the bare lattice or the bare carrier, but arise from their mutual reorganisation over femtoseconds to picoseconds. Rather than simply characterising the final state, we use ultrafast transient absorption experiments to track this process - watching a carrier dress itself in lattice distortion, a coherence develop and decay, an exciton cross from free to self-trapped. This real-time vantage has revealed that Au–Br stretching phonons drive slow polaron formation in lead-free caesium gold bromide (Advanced Optical Materials, 2025), and that reducing dimensionality from 2D to 1D in organic-inorganic tin halides switches the lattice response from silent to dominant, activating self-trapping through a specific wagging mode (Nature Communications, 2025).
Chiral Quantum Photonics
Chirality - optical handedness - is absent from an inorganic perovskite lattice on its own and it emerges at the interface: when a chiral organic cation couples to an inorganic framework across a hydrogen-bond network. We studied these interfaces as productive sites rather than boundaries, asking what crosses them (angular momentum, phonon character, coherence), on what timescale, and what optically active property the coupled system acquires that the inorganic lattice didn't possess alone. The goal is to understand chirality transfer with sufficient mechanistic precision to design interfaces that maximise chiral optical states for applications in quantum information and spin-selective transport.
Control of Energy Flow in Nanostructures
How energy moves through a nanostructured material is not determined by composition alone, it is also determined by architecture: the stacking sequence of quantum wells, the connectivity between sites, the spatial arrangement of donors and acceptors. We study energy flow as an emergent collective behaviour, one that switches character entirely when structural organisation changes - from diffusive hopping to cascading, from photon recycling to directed funnelling - using ultrafast spectroscopy to resolve which pathway dominates and why. Prior work has disentangled photon recycling from exciton hopping in perovskite nanocrystal films (Light: Science & Applications, 2021) and identified interlayer exciton delocalisation as the driver of ultrafast energy funnelling in Ruddlesden-Popper quantum-well stacks (Nano Letters, 2021); We are interested in how deliberately engineered structural motifs — e.g. moiré superlattices, chiral stacking sequences, plasmonic near-field gradients — can be used to route energy directionally.
Ultrafast Optical Spectroscopy
What enables our research is ultrafast optical spectroscopy. It consists of a suite of experimental techniques where sequences of ultrashort light pulses (with femtosecond durations) excite and interrogate photoinduced dynamical processes in atoms, molecules, nanostructures, and solids.
The observable is usually light emission or absorption from a material. It is recorded as a function of time using advanced photonic and electronic tools.
The data is then analysed rigorously and interpreted, usually with backing of theory and complementary characterisation.
The pump-probe technique, shown above, is a widely used technique to study transient changes in absorption of a material, that can be used to understand dynamics of photo-induced excitation.