Physics colloquium-“Quantum Optics Meets Strong Field Physics: Novel Regimes of Coherent X-ray Generation with Strong Electron Correlation Dynamics and Attosecond Rabi Oscillations”

Tenio Popmintchev

University of California, San Diego

Abstract: Ultrafast imaging and spectroscopies using coherent EUV – X-ray light based on the nonlinear
process of high harmonic generation are already addressing grand challenges in complex molecular
systems, plasmas, and advanced nanomaterials. The exquisite quantum control of the attosecond dynamics
of the rescattering electrons in this extreme frequency upconversion makes it possible to sculpt the classical
and quantum properties of the light with unprecedented tunability of the spectral, spatial, temporal shape,
and spin and orbital angular momentum state. The superb coherence of this unique light allows for multidimensional imaging at the space-time extreme with 4D resolution of nanometers and femtoseconds,
including access to an effective 5th dimension – the periodic table of elements – due to the X-ray absorption
fingerprinting with elemental and chemical specificity. In this talk, I will present two novel quantum regimes of coherent X-ray generation where the design of the light properties is dominated by the dynamics of the entangled electrons in a simple He atomic system. Interestingly, the physics of these regimes extends beyond the well-established three-step high harmonic model. In the first regime, using strong UV laser fields, the entangled electron dynamics yield a characteristic plateau in the X-ray spectral region, extending well beyond the conventional cutoff. This is due to simultaneous double electron recombination where a single high-energy X-ray photon is emitted only in atomic systems with strongly correlated electrons. This low probability phenomenon paves a way to a sensitive attosecond spectroscopy as a probe of highly correlated interactions. Similar physics of high harmonics from solids might be able to characterize electron correlations in phase transition materials and nanosystems of relevance to quantum computing and superconductivity.
In the second extreme regime, using intense EUV driving fields tuned to a resonance frequency of
He can result in very bright harmonic emission in the X-ray regime. Favorable quantum dynamics of the
electron wavepackets, and phase and group velocity matching of the light fields enhance the X-ray yield.
Furthermore, record-fast attosecond Rabi oscillations are predicted to suppress the depletion of the ground
state, which otherwise terminates the emission of X-ray photons. These new advances in quantum control over the coherent X-ray emission enable new insights into complex entangled electron dynamics and applications in nanoscience and quantum technology.

BIO: Prof. Tenio Popmintchev is an Assistant Professor in the Physics Department and the Center for Advanced Nanoscience at the University of California San Diego. He received his PhD in Atomic, Molecular, and Optical Physics from the JILA Institute and University of Colorado Boulder in 2010, where he conducted pioneering research on ultrashort pulse lasers and bright coherent X-ray generation with designer classical and quantum properties. Prof. Popmintchev is an internationally recognized leader in the field of Attosecond and X-ray Science. He has over 90 publications, including papers in Science, Nature Photonics, Nature Physics, and Physical Review Letters. Some of his honors include the Sloan Research Fellowship, European Research Council Starting Grant, Science News USA 10 Outstanding Young Scientist Award, Presidential Medal for Pioneering Contribution to Science and Technology. Prof. Popmintchev led groundbreaking work on scaling EUV attosecond pulses towards generating attosecond-to-zeptosecond X-ray pulses in the keV regime – the shortest events ever created in a laboratory. His research on developing bright coherent EUV and X-ray light with tunable spectral, spatial, and temporal shape, and tunable angular momentum, has been enabling new capabilities for ultrafast multidimensional imaging and spectroscopies at the space-time resolution extreme. Some of his current research directions expand towards novel quantum regimes of X-ray generation, merging quantum optics and strong field physics.

All lectures in Hill Hall 202 unless otherwise specified