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Research news
Interaction-induced Thouless pumping
In a joint theory-experiment collaboration between the ETH Zurich, Centro Atomico Bariloche and our group published in Phys. Rev. X 14, 021049 (2024) , we demonstrate interaction induced charge pumping in a system of interacting fermions in a quantum gas experiment, supported by numerical simulations for realistic conditions. This constitutes one of the first instances of topology in an interacting system. The initial quantized pumping is eventually surpassed by a breakdown due low-energy spin excitations, rooted in the many-body physics of the ionic Hubbard model. The figure shows a sketch of the experimental set-up.
Dynamical quantities of electron phonon systems
In our recent study Jansen et al., Phys. Rev. B 102, 165155 (2020) , we use a density-matrix renormalization group method combined with local basis optimization to efficiently compute thermodynamic expectation values and finite-temperature spectral functions of the Holstein polaron model. Focusing on the intermediate electron-phonon coupling regime, we first test our approach by comparing the spectral function to that obtained with the finite-temperature Lanczos method. We then compute the electron-emission spectrum and the phonon spectral function. As temperature is increased, we observe that spectral weight is shifted to lower frequencies and larger momenta for the electron-emission spectrum. For the phonon spectral function, larger temperatures allow us to observe a reflected polaron band.