MBI Colloquium

Mittwoch, 19. März 2025 // 14.00 -

Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie

Max-Born-Straße 2a, 12489 Berlin
Max Born Hall

Coupling magnons and phonons

Dr. Urs Staub | Paul Scherrer Institute, Villigen, Switzerland

Magnons and phonons are fundamental quasi-particles in solids and of central importance to understand the magnetic, electronic and structural properties of quantum materials. Here, I address cases of coupling them, specifically when both time and space inversion symmetries are broken and how x-rays can contribute to their microscopic understanding. This is achieved using spectroscopic techniques in the energy window, as well as in real time using ultrashort x-ray pulses created by PSI’s X-ray free electron laser SwissFEL.

In the first example, I will show how one can resonantly drive an electromagnon and how to probe the phononic wave function of the electromagnon based on time resolved X-ray diffraction. This can be combined with the response of the spin system using time resolved resonant magnetic x-ray diffraction, which allows us to disentangle lattice and magnetic excitation in these types of composite mode. [1]

The second example addresses the properties of chiral/circular phonons, which intrinsically break time reversal symmetry. I show different approaches how we can/could directly observed them, some successful [2] and others not (yet?), including the first direct real time observation of driven ultrafast circulating atomic motions in a solid.

If there is time left, I will show how we can directly drive orbitals using the magnetic field of a THz pulse. The response after the excitation results in quantum interference of the “two energy levels” seen through a time dependent antiferromagnetic x-ray scattering signal with the frequency of the two-level energy separation. [3]

[1] Hiroki Ueda, Roman Mankowsky, Eugenio Paris, Mathias Sander, Yunpei Deng, Biaolong, Liu, Ludmila Leroy, Abhishek Nag, Elizabeth Skoropata, Chennan Wang Victor Ukleev, Gérard Sylvester Perren, Janine Dössegger, Sabina Gurung, Cristian Svetina, Elsa Abreu, Matteo Savoini, Tsuyoshi Kimura, Luc Patthey, Elia Razzoli, Henrik Till Lemke, Steven Lee Johnson, and Urs Staub, Nature Commun. 14, 7778 (2023).

[2] Hiroki Ueda, Mirian García-Fernández, Stefano Agrestini, Carl P. Romao, Jeroen van den Brink, Nicola A. Spaldin, Ke-Jin Zhou, and Urs Staub, Nature 618, 946 (2023).

[3] R. Mankowsky, M. Müller, M. Sander, S. Zerdane, X. Liu1, D. Babich, H. Ueda, Y. Deng, R. Winkler, B. Strudwick, M. Savoini, F. Giorgianni, S. L. Johnson, E. Pomjakushina, P. Beaud, T. Fennel, H.T. Lemke, and U. Staub, Nature Commun. 15, 7183 (2024)