Research
Formulating and implementing theory for quantum phenomena in materials
I build theoretical frameworks — and the code that makes them usable — to explain how quantum materials absorb light, emit light, and carry current without resistance. Three threads run through the work.
Theoretical spectroscopy
I study the optical properties of two-dimensional multilayer structures built from transition metal dichalcogenides (TMDs) and topological insulators such as Bi₂Se₃. Reduced dimensionality and dielectric screening enhance the Coulomb interaction between charge carriers, producing strongly bound electron–hole pairs — excitons — that dominate the optical response.
Concretely, I work on:
- Excitonic response of heterostructures — how stacking order, twist angle and interlayer distance reshape the exciton spectrum (Phys. Rev. B 110, 035118).
- Real-time photoluminescence from non-equilibrium many-body perturbation theory, implemented in the Yambo code.
- Ultrafast carrier dynamics in 2D Bi₂Se₃ nanoplatelets, in collaboration with experiment (ACS Nano 19, 17261).
Light and matter on the same footing
An optical experiment splits the Universe in two. The laser and the detector form a classical external world, which enters only through prescribed potentials. The crystal is quantized: electrons, nuclei and transverse photons, described by quantum electrodynamics in a Born–von Kármán volume. The laser’s transverse field drives a transverse current in the crystal. That current radiates, and the detector records the total field, source plus induced.
The exact ground state of this system is a dressed photon state that is orthogonal to the free photon vacuum in the thermodynamic limit, so perturbation theory built on the vacuum fails. A canonical transformation absorbs the photon dressing and leaves a purely fermionic transverse matter Hamiltonian, where photons are replaced by an instantaneous, screened current–current interaction. Absorption then follows from the transverse current–current response, the photon self-energy, and the macroscopic dielectric function comes out in a form where every excitation line has positive weight.
Superconductivity
I combine Bogoliubov–de Gennes theory with density functional theory in a unified approach — density functional Bogoliubov–de Gennes theory (DFT-BdG) — which I extended to unconventional pairing and implemented in the SIESTA code (Phys. Rev. B 110, 134505).
Applications include proximity-induced superconductivity in semiconductor– superconductor heterostructures such as PbTe/Pb, relevant to topological quantum computing platforms (Phys. Rev. B 113 (2026)).
Gauges and topology
Many quantities in physics depend on a choice nobody can measure: the gauge of the electromagnetic potentials, or the phases of Bloch states across the Brillouin zone. Observables cannot depend on that choice, and working out what survives it is often where the physics is. Fixing a gauge well (Coulomb, velocity or length gauge for light–matter coupling, or smooth Bloch phases for Wannier functions) makes a theory tractable and its approximations controlled. When a smooth, global gauge does not exist, the obstruction is itself physical: Berry phases, Berry curvature and Chern numbers are topological invariants that fix quantized responses and protected boundary states.
I use this language in two directions: to choose representations of the light–matter problem in which approximations stay gauge-invariant, and, through Wannier-based tight-binding models interfaced with first-principles calculations, to connect band geometry and topology to measurable spectra.
Codes and tools
| Code | Role |
|---|---|
| Yambo / yambopy | GW, BSE, real-time dynamics — developer |
| SIESTA | DFT-BdG for superconductors — developer |
| Quantum ESPRESSO | Ground-state DFT and phonons |
| Wannier90 | Maximally localised Wannier functions |
| AiiDA | High-throughput workflow management |