FLEET Research Fellow Dr Eliezer Estrecho
In this poster, I will present the first measurement of the novel topological invariant that is unique to non-Hermitian systems. Topology arises in Hermitian systems from the winding of eigenstates in momentum space. The extension of the eigenvalues of non-Hermitian systems to complex space gives birth to a new topology arising from the winding of the complex energies. Nontrivial winding occurs near non-Hermitian degeneracies called exceptional points, where, not only the eigenvalues, the eigenstates become one. The underlying topology of exceptional points have been explored before but indirectly by exploring the eigenstates. In this work, by carefully measuring the energies (real part) and linewidths (imaginary part) of the polarisation modes of exciton polaritons based on lead-halide perovskites, we directly measured the novel topological invariant, also called ‘spectral vorticity’, in momentum space. This paves the way for studying the non-Hermitian topology in many-body systems, which can lead to novel topologically robust phenomena, e.g. that can be combined with superfluidity.
About the presenter
Eliezer Estrecho studies the behaviour of exciton-polaritons as part of FLEET’s research theme 2, exciton superfluids, working with Elena Ostrovskaya at the ANU. He is currently studying condensation of polaritons in gallium-arsenide-based microcavities using single-shot experiments and large optically induced traps. He is also working on creating polariton condensates using atomically-thin materials.