Attosecond light science and its application for probing quantum materials

We gratefully acknowledge support from the National Science Foundation through the JILA Physics Frontiers Center PHY-1734006, and a Gordon and Betty Moore Foundation EPiQS Award GBMF4538, for the attosecond ARPES setups and methods. We gratefully acknowledge support from the Department of Energy Office of Basic Energy Sciences XRay Scattering Program Award DE-SC0002002 for the spin dynamics setups and methods. We gratefully acknowledge support from the Department of EnergyOffice of Basic Energy Sciences AMOS Award DE-FG02-99ER14982 (experiment) as well as an MURI Grant from the Air Force Office of Scientific Research under Award Number FA9550-16-1-0121 (theory) for the HHG light source setups and methods. The authors gratefully acknowledge support from the STROBE National Science Foundation Science and Technology Center, Grant No. DMR-1548924, for the imaging setups and methods. C H-G acknowledges support by Ministerio de Ciencia, Innovación y Universidades for projects (FIS2016-75652-P and PID2019-106910GB-I00) and a Ramon y Cajal contract (RYC-2017-22745), co-funded by the European Social Fund; Junta de Castilla y León and European Union, FEDER, (Project SA287P18); and from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant agreement No. 851201). ZT gratefully acknowledges the financial support from the National Natural Science Foundation of China (Grant No.11874121), the Shanghai Municipal Science and Technology Basic Research Project (Grant No. 19JC1410900) and the Alexander-von-Humboldt foundation.
In this paper, we review the development and application of coherent short wavelength light sources implemented using the high harmonic generation (HHG) process. The physics underlying HHG brought quantum physics into the domain of attosecond time-scales for the first time. The observation and manipulation of electron dynamics on such short time-scales—a capability not conceived—of just a few decades ago—is becoming both more-and-more sophisticated and useful as a route to achieve exquisite control over short wavelength light. New experimental techniques are enabling HHG light sources to provide new insights into fundamental quantum interactions in materials, making it possible for the first time to capture the fastest charge, spin, photon and phonon interactions and to achieve diffraction-limited imaging at short wavelengths.