Nagaoka ferromagnetism observed in a quantum dot plaquette.

Autor: Dehollain JP; QuTech, TU Delft, Delft, The Netherlands.; Kavli Institute of Nanoscience, TU Delft, Delft, The Netherlands.; School of Mathematical and Physical Sciences, University of Technology Sydney, Sydney, New South Wales, Australia., Mukhopadhyay U; QuTech, TU Delft, Delft, The Netherlands.; Kavli Institute of Nanoscience, TU Delft, Delft, The Netherlands., Michal VP; QuTech, TU Delft, Delft, The Netherlands.; Kavli Institute of Nanoscience, TU Delft, Delft, The Netherlands., Wang Y; Department of Physics, Harvard University, Cambridge, MA, USA., Wunsch B; Department of Physics, Harvard University, Cambridge, MA, USA., Reichl C; Solid State Physics Laboratory, ETH Zürich, Zürich, Switzerland., Wegscheider W; Solid State Physics Laboratory, ETH Zürich, Zürich, Switzerland., Rudner MS; Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark.; Niels Bohr International Academy, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark., Demler E; Department of Physics, Harvard University, Cambridge, MA, USA., Vandersypen LMK; QuTech, TU Delft, Delft, The Netherlands. l.m.k.vandersypen@tudelft.nl.; Kavli Institute of Nanoscience, TU Delft, Delft, The Netherlands. l.m.k.vandersypen@tudelft.nl.
Jazyk: angličtina
Zdroj: Nature [Nature] 2020 Mar; Vol. 579 (7800), pp. 528-533. Date of Electronic Publication: 2020 Mar 02.
DOI: 10.1038/s41586-020-2051-0
Abstrakt: Engineered, highly controllable quantum systems are promising simulators of emergent physics beyond the simulation capabilities of classical computers 1 . An important problem in many-body physics is itinerant magnetism, which originates purely from long-range interactions of free electrons and whose existence in real systems has been debated for decades 2,3 . Here we use a quantum simulator consisting of a four-electron-site square plaquette of quantum dots 4 to demonstrate Nagaoka ferromagnetism 5 . This form of itinerant magnetism has been rigorously studied theoretically 6-9 but has remained unattainable in experiments. We load the plaquette with three electrons and demonstrate the predicted emergence of spontaneous ferromagnetic correlations through pairwise measurements of spin. We find that the ferromagnetic ground state is remarkably robust to engineered disorder in the on-site potentials and we can induce a transition to the low-spin state by changing the plaquette topology to an open chain. This demonstration of Nagaoka ferromagnetism highlights that quantum simulators can be used to study physical phenomena that have not yet been observed in any experimental system. The work also constitutes an important step towards large-scale quantum dot simulators of correlated electron systems.
Databáze: MEDLINE
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