RIXS spectroscopy observes new type of excitation channel

The Heisenberg spin chain is one of the simplest models in quantum mechanics. It comprises a chain of interacting spinning particles such as electrons whose spins align to each other. An international group of researchers has now used an X-ray scattering technique called RIXS to observe a novel pathway of changing the alignment of spins. "This offers the potential to explore a whole new world of unknown quantum states", says European XFEL scientist Justine Schlappa, the first author of the study. The results were published this week in Nature Communications.

Spin chains explain, for example, how interactions in quantum materials such as those relevant for magnetism work. In magnetic materials, electrons all spin in the same direction, resulting in a net magnetic field. A Heisenberg chain is like a linear network of sections with regularly arranged spins. Each spin is strongly coupled to the two direct neighbours, so that if one spin is flipped, the spin direction of its neighbours will turn as well, resulting in a propagation of the disturbance throughout the chain. Such a spin disturbance can be induced or 'excited' by various external influences, including X-rays.

Resonant inelastic X-ray scattering (RIXS) is a spectroscopy technique that provides information about the distributions of these excitations. In the experiment described in the new publication, the scientists used RIXS to observe a novel pathway to induce spin excitations that is not possible to observe with other methods. RIXS therefore offers the potential to explore a whole new world of unknown quantum states, potentially helping with the development of quantum computers and new solutions for data storage. Studies of such states will be soon possible with the Heisenberg RIXS (hRIXS) spectrometer currently being built for the SCS instrument at European XFEL, and planned for installation in 2019. This will be the only such instrument currently available at free-electron laser sources. Members of the hRIXS User Consortium, whose activities from the European XFEL side are coordinated by Justine Schlappa, are among others the University of Potsdam, DESY, and the University of Milan. The SCS instrument started operation in December 2018.

Source: European XFEL GmbH