Dr Wojciech Brzezicki (ON6 MagTop) gave a theoretical contribution to a Nature publication concerning an exotic surface chiral phase of Sr2RuO4. This hypothetical phase containing ground-state spin-orbital currents breaks both time-reversal and all crystalline symmetric, hence the name chiral. The method to observe such symmetry-broken state is circularly-polarized angular- and spin-resolved photoemission experiment (CP-spin-ARPES). The difference of measured intensity between left and right polarization gives what is called circular dichroism (CD). Its intensity can be related to the electron’s average angular momentum and typically takes opposite sign for opposite quasimomenta. The main finding of Dr Brzezicki’s work is that in presence of the ground-state spin-orbital currents CD exhibits this usual behavior whereas spin-resolved CD does not. Therefore CP-spin-ARPES has capacity to detect such an unusual order.
[F. Mazzola, W. Brzezicki, M. T. Mercaldo, A. Guarino, C. Bigi, J. A. Miwa, D. De Fazio, A. Crepaldi, J. Fujii, G. Rossi, P. Orgiani, S. Kumar Chaluvadi, S. P. Chalil, G. Panaccione, A. Jana, V. Polewczyk, I. Vobornik, Ch. Kim, F. Miletto-Granozio, R. Fittipaldi, C. Ortix, M. Cuoco, A. Vecchione, Signatures of a surface spin–orbital chiral metal, Nature (2024)]