Spin-Resolved Momentum Microscopy at NTNU and Polaronic Quasiparticles in mixed-valent TmSe_{1-x}Te_{x}

Chul-Hee Min — NTNU, Trondheim, Norway

In this talk I will present two sets of results from our group. First, I will introduce our laser-based spin-ARPES instrument at NTNU, which combines a 6 eV continuous-wave laser with full polarization control and a momentum microscope equipped with a 2D imaging spin-filter. This setup enables parallel, multi-channel acquisition of spin-resolved photoelectron distributions across the full k-space in a single measurement, drastically reducing acquisition times compared to conventional single-channel spin detectors. Using Bi₂Cu/Cu(111) and Sb(111) as benchmark systems, I will demonstrate full spin-texture mapping across the Brillouin zone with high efficiency, including the simultaneous extraction of all in-plane spin vector components. In the second part, I will report the first spectroscopic evidence of Holstein polarons in mixed-valent TmSe_1−xTe_x, revealed by high-energy-resolution hard X-ray (6 keV) and XUV (110 eV) photoemission. Anomalous spectral lineshapes in the semimetallic phase, unexplained by standard many-body theories, are quantitatively reproduced within the Holstein polaron model. These results highlight the need to incorporate electron–phonon coupling into the periodic Anderson model to fully capture quasiparticle formation in rare-earth systems, and open new avenues for exploring polaronic physics in mixed-valent metals.