When: Tuesday, May 15, 2018, 2:30 pm
Location: MPQ Garching, New Lecture Hall, Room B 0.32
M.Sc. Joannis Koepsell (PhD, Quantum Many-Body Systems Division ) and Dr. Oleg Pronin (Scientist, LAP) will talk about
"Direct observation of incommensurate magnetism in Hubbard chains" (M.Sc. J. Koepsell) and "Utlrafast thin-disk oscillators at 1 µm and 2 µm wavelengths" (Dr. O. Pronin).
Direct observation of incommensurate magnetism in Hubbard chains (M.Sc. Joannis Koepsell)
The interplay between magnetism and doping is at the origin of exotic strongly correlated electronic phases and can lead to novel forms of magnetic ordering.One example is the emergence of incommensurate spin-density waves with a wave vector that does not match the reciprocal lattice. In one dimension this effect is a hallmark of Luttinger liquids, also describing the low energy physics of the Hubbard model. Here we use a quantum simulator based on ultracold fermions in an optical lattice to directly observe such incommensurate spin correlations in doped and spin-imbalanced Hubbard chains using fully spin and density resolved quantum gas microscopy. Doping is found to induce a linear change of the spin-density wave vector in excellent agreement with Luttinger theory predictions. For non-zero polarization we observe a decrease of the wave vector with magnetization as expected from the Heisenberg model in a magnetic field. We trace the microscopic origin of these incommensurate correlations to holes, doublons and excess spins which act as delocalized domain walls for the antiferromagnetic order. Finally, when inducing interchain coupling we observe fundamentally different spin correlations around holes and doublons indicating the formation of a magnetic polaron.
Utlrafast thin-disk oscillators at 1 µm and 2 µm wavelengths (Dr. Oleg Pronin)
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