Time-of-flight momentum microscope

• Subject Area: Condensed Matter Physics
• Term: Funded in 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 567410469

Lightwave electronics has the potential to enable future information technology at optical clock rates, which can be hundreds of thousands of times faster than present-day commercial CMOS devices. The key idea is to employ the carrier field of intense light pulses as an alternating bias field to control electrons faster than an oscillation period of light. On such short times scales, electrons can barely scatter even in the dense many-body system of a solid. Thus, lightwave electronics opens a unique door to a completely coherent quantum world. The time-of-flight momentum microscope which we are applying for will be used to visualize the quantum motion of lightwave-accelerated electrons directly in the band structure. To this end, the photoelectron spectrometer will be operated in combination with an existing high-power ultrafast laser system, which simultaneously generates highly intense phase-locked terahertz and mid-infrared pulses, vacuum ultraviolet probe pulses and tunable ultrafast excitation pulses in the visible domain. This way, we will develop a unique setup for subcycle band-structure videography of crystalline solids. In contrast to angle-resolved photoelectron spectroscopy (ARPES) using hemispherical electron analyzers, the time-of-flight momentum microscope will map out the electronic band structure of crystalline solids throughout the entire first Brillouin zone, at once. Based on our recent subcycle ARPES experiments [Nature 562, 396 (2018), Nature 616, 696 (2023)], we will record first-ever femtosecond slow-motion movies of lightwave-driven electrons while they are accelerated through the entire band structure of solids. In a broad variety of modern quantum materials, such as graphene, transition metal dichalcogenides, van der Waals heterostructures, topological insulators, chiral Weyl semimetals and correlated electron systems, key aspects of ultrafast electron dynamics well be revealed directly on the relevant time, momentum and energy scales. Examples range from the observation of dynamical Bloch oscillations and relativistic Zitterbewegung to ultrafast switching dynamics of the valley pseudospin or phase transitions in correlated electron systems, directly in the band structure. The time-of-flight momentum microscope is a strategic centerpiece for the exploration of emergent relativistic effects in condensed matter at the University of Regensburg. The instrument will, thus, benefit the Collaborative Research Center 1277 while also strengthening the Research Training Group 2905.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Flugzeit-Impulsmikroskop
• Instrumentation Group: 1780 Photoelektronenspektrometer (UPS und XPS)
• Applicant Institution: Universität Regensburg
• Leader: Professor Dr. Rupert Huber