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Quantum optics

Quantum magnets doped with holes

München, 08/04/2017

Munich based scientists reveal hidden magnetic order in one-dimensional quantum crystals doped with holes.

Image of a chain of atoms taken with the quantum gas microscope. It demonstrates that atoms with different spin orientations are spatially separated. If the spin points downwards (green), the atom is located in the lower part of the double well structure of the lattice site, whereas it is in the upper part, if the spin points upwards (red). In addition, the holes can be detected directly. Source:

Magnetism is a phenomenon that we experience in everyday-life quite often. The property, which is observed in materials such as such as iron, is caused by the alignment of electron spins. Even more interesting effects are expected in case that the magnetic crystals exhibit holes, i.e., lattice sites that are not occupied with an electron. Because of the interplay between the motion of the defect and the magnetic correlations of the electron spins, the magnetic order seems to be suppressed. In general, solid state physicists are not able to separate the two processes, so they cannot answer the question, whether the magnetic order is indeed reduced, or whether it is just hidden.

Now a team of scientists around Dr. Christian Groß from the Quantum Many-Body Systems Division at the Max Planck Institute of Quantum Optics (MPQ) and Professor Immanuel Bloch, Chair of Quantum Optics at LMU Munich and Director at MPQ, has demonstrated that in one-dimensional quantum magnets the magnetic order is preserved even when they are doped with holes – a direct manifestation of spin-charge (density) separation. The quantum crystals were prepared by chains of ultracold atoms in an optical lattice. The observation was made possible with a unique tool which allows tracking the motion of holes and the spin excitations separately in one measurement process. (MPQ/LMU)
Science 2017

Press release of the Max Planck Institute of Quantum Optics