Quantum simulator to study electronic structure - from molecules to lattices to the Hofstadter butterfly
Prof. Daniel Wegner
Institute for Molecules and Materials, Radboud Universiteit
16:15 - 17:15 Tuesday 11 November 2025 TUG HS P2 Quantum simulators are a pathway to study novel physical phenomena which are difficult to predict or observe in synthesized materials. To this end, the physical behavior of materials ranging from gasses to superconducting qubits has been used to emulate Hamiltonians. A promising route is to create bottom-up platforms based on assembling adsorbates on surfaces via the atomic manipulation capabilities in scanning tunneling microscopy (STM). This way, tunable artificial atoms, molecules and lattices can be created, and their electronic properties can be studied by means of scanning tunneling spectroscopy (STS).
In my talk, I will introduce a novel solid state quantum simulator based solely on patterned Cs atoms on the surface of semiconducting InSb(110). We use this platform to locally bind electrons in traps that emulate artificial atoms, by precisely positioning Cs atoms with the STM tip [1]. The bound localized states are probed and mapped via STS. These artificial atoms serve as building blocks to realize artificial molecular structures with different orbital symmetries. We realize textbook examples of molecular physics such as bonding/anti-bonding splitting in dimers, higher orbital symmetries (px,py, sp2 hybrids) and the emulation of entire organic molecular electronic structure (e.g.benzene, cis-, trans, and cyclobutadienes, triangulene). I will discuss the transition from the molecular limit to band formation in extended artificial structures, and I will give an outlook of our most recent studies in strong magnetic fields, where we can observe Fock-Darwin states and Hofstadter bands.
[1] E. Sierda et al., Science 380, 1048 (2023).
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