From Photoemission Microscopy to an “All-in-One” Photoemission Experiment

Abstract

Photoelectron spectroscopy is our main tool to explore the electronic structure of novel material systems, the properties of which are often determined by an intricate interplay of competing interactions. Elucidating the role of this interactions requires studies over an extensive range of energy, momentum, length, and time scales. We show that immersion lens-based momentum microscopy with spin-resolution is able to combine these seemingly divergent requirements in a unifying experimental approach. We will discuss applications to different areas in information research, for example, resistive switching and spintronics. The analysis of resistive switching phenomena in oxides requires high lateral resolution and chemical selectivity, as the processes involve local redox processes and oxygen vacancy migration. In spintronics topological phenomena are currently a hot topic, which lead to complex band structures and spin textures in reciprocal space. Spin-resolved momentum microscopy is uniquely suited to address these aspects.

Link between Weyl-fermion chirality and spin texture

“…Pho-toelectrons emitted into the complete solid angle above the sample surface were collected using a momentum microscope [46]. Spin-resolved photoelectron maps were measured using a W(100) imaging spin filter combined with momentum microscopy [27,29,47,48]. Spin polarization (P ) is detected along the k y in-plane direction in the light incidence plane, as shown in Fig.…”

“…Spin-resolved experiments for such materials with highest resolution have for a long time been hindered by the inefficiency of available photoemission spectroscopy tools. This situation has only recently been overcome by the advent of advanced electron spin analysers [26][27][28][29]. Overall, the relationship between the spin texture and topological chiral charges in Weyl semimetals has still remained elusive.…”

Hard x-ray photoelectron spectroscopy: a snapshot of the state-of-the-art in 2020

“…The main difference being that here the image plane is being projected onto the detector, while in momentum microscopy the back focal plane is imaged and in many cases, both types of imaging can be realised with the same instrument. [253,254] The first HAXPEEM instrument began operation at beamline P09 at PETRAIII and was relocated to beamline P22 in 2018. [57,255] This microscope is based on a NanoESCA instrument (Scienta Omicron GmbH / FOCUS GmbH) modified to operate at higher electron energies.…”

The 2021 ultrafast spectroscopic probes of condensed matter roadmap

“…Similarly, for TR-PEEM, the need to only image photoelectrons from specific regions in the BZ brings in angle-resolution considerations to PEEM measurements. While some of these instrumentation capabilities are now available [142], further development is continuously occurring to combine and enhance more aspects of photoemission spectroscopy, including the tantalizing possibility of adding spin-resolution to the mix [132].…”