About

Alexandra Landsman is a professor in the Department of Physics at The Ohio State University. Her research focuses on studying the dynamics that occur when ultrashort light pulses, on the time scale of attoseconds (10^(-18) seconds) to femtoseconds (10^(-15) seconds), interact with atoms, molecules, and condensed matter systems. These ultrashort flashes of light enable the capture of the motion of bound electrons inside matter, providing a new perspective on extremely small objects and fast processes. Her ultimate goal is to achieve accurate imaging and control of electron dynamics on the attosecond time-scale. Her work employs a variety of numerical and analytic methods, including solutions of the Schrödinger equation, classical and semiclassical approaches, and techniques from nonlinear dynamical systems. Her research contributes to the understanding of electron motion and dynamics at the quantum level, advancing the field of ultrafast optics and atomic, molecular, and condensed matter physics.

Research topics

• Quantum mechanics
• Atomic physics
• Physics
• Optics

Selected publications

• Effect of spin polarization on tunneling delay in attoclock settings

  New Journal of Physics · 2026-03-01

  articleOpen accessSenior author

  Abstract We investigate how spin polarization of the initial atomic state affects the tunneling delay in the attoclock settings. Using the time dependent Schrödinger equation and the Breit–Pauli Hamiltonian we demonstrate that spin polarization can produce measurable corrections to tunneling delays in attoclock spectroscopy. Our findings indicate that spin–orbit coupling introduces an additional spin-dependent degree of freedom into under-the- barrier motion, suggesting new opportunities for spin-resolved attosecond measurements. We show that the electron’s spin orientation during tunneling produces a contribution to the attoclock offset angle. Our results are interpreted within the framework of the strong field approximation and the imaginary time methods. We show that this approach provides a rare opportunity to get an insight into the details of the sub-barrier electron motion during the tunneling process.

  PublisherOA PDFDOI

• Disentangling High Harmonic Generation from Surface and Bulk States of a Topological Insulator

  arXiv (Cornell University) · 2026-04-07

  articleOpen access

  The discovery of topological phases has introduced a new dimension to materials science. Three-dimensional (3D) topological insulators (TIs) are a remarkable class of matter that is insulating in the bulk while hosting conductive topological surface states (TSSs) with unique charge and spin properties. High-order harmonic generation (HHG) has emerged as a powerful tool to probe condensed matter systems by providing insights into their electronic structure and dynamic behavior. Here, we investigate HHG in the prototype 3D-TI Bi$_2$Se$_3$. We demonstrate that the contributions of bulk and surface states to the harmonic emission can be controlled by tuning the thickness of thin film samples. An ultrathin (6 nm) film substantially enhances HHG from the surface states, while the bulk states dominate HHG in a thicker (50 nm) film. By applying a quasi-static terahertz perturbing field, we disentangle the bulk and surface responses and reveal the significant impact of the surface states' shift vector and Berry curvature on HHG. Our study provides effective methods for isolating the optical responses of TSSs from those of the bulk, which opens the door to resolving an ongoing debate regarding whether it is possible to reliably extract topological signatures in HHG.

  PublisherOA PDF

• Supplementary document for Analytical description of phase in high-order harmonic generation: nonadiabatic effect on single atom response and macroscopic phase matching - 7853375.pdf

  Figshare · 2026-04-06

  articleOpen access

  Supplemental Document

  PublisherDOI

• Analytical description of phase in high-order harmonic generation: nonadiabatic effect on single atom response and macroscopic phase matching

  Optics Express · 2026-03-31

  articleOpen access

  We propose a fully analytical expression for the phase of high-order harmonic generation (HHG) within the framework of the strong-field approximation (SFA), which clearly separates the nonadiabatic contribution from the adiabatic one. At the single-atom response level, we show that the nonadiabatic phase leads to a significant shift in the photon energy corresponding to the peak of the HHG spectrum, a phenomenon that can be attributed to the interference of different quantum trajectories. The analytical expression for the nonadiabatic phase also provides further theoretical support for reconstructing electron dynamics (excursion time) from HHG spectra generated using mixed gases. At the macroscopic level, our approach yields a fully analytical nonadiabatic expression for atomic dipole phase matching, which can accurately predict the HHG phase-matching condition and shows good agreement with both experiments and numerical SFA simulations. In particular, this expression explicitly reveals how the HHG phase depends on laser and atomic parameters. This may enable more convenient control of the HHG phase by adjusting laser parameters in future experiments aimed at attosecond pulse generation and the development of coherent high energy light sources.

  PublisherDOI

• Replication Data for Single Trajectory Delays

  Harvard Dataverse · 2026-01-16

  datasetOpen accessSenior author

  Contains the raw delay values for numerical electron trajectory calculations to describe attosecond streaking for infrared wavelengths of 800 nm and 400 nm.

  PublisherDOI

• Supplementary document for Analytical description of phase in high-order harmonic generation: nonadiabatic effect on single atom response and macroscopic phase matching - 7853375.pdf

  Figshare · 2026-04-06

  articleOpen access

  Supplemental Document

  PublisherDOI

• Disentangling High Harmonic Generation from Surface and Bulk States of a Topological Insulator

  arXiv (Cornell University) · 2026-04-07

  preprintOpen access

  The discovery of topological phases has introduced a new dimension to materials science. Three-dimensional (3D) topological insulators (TIs) are a remarkable class of matter that is insulating in the bulk while hosting conductive topological surface states (TSSs) with unique charge and spin properties. High-order harmonic generation (HHG) has emerged as a powerful tool to probe condensed matter systems by providing insights into their electronic structure and dynamic behavior. Here, we investigate HHG in the prototype 3D-TI Bi$_2$Se$_3$. We demonstrate that the contributions of bulk and surface states to the harmonic emission can be controlled by tuning the thickness of thin film samples. An ultrathin (6 nm) film substantially enhances HHG from the surface states, while the bulk states dominate HHG in a thicker (50 nm) film. By applying a quasi-static terahertz perturbing field, we disentangle the bulk and surface responses and reveal the significant impact of the surface states' shift vector and Berry curvature on HHG. Our study provides effective methods for isolating the optical responses of TSSs from those of the bulk, which opens the door to resolving an ongoing debate regarding whether it is possible to reliably extract topological signatures in HHG.

  PublisherDOI

• Analytical description of phase in high-order harmonic generation: nonadiabatic effect on single atom response and macroscopic phase matching

  Figshare · 2026-04-06

  otherOpen access

  We propose a fully analytical expression for the phase of high-order harmonic generation (HHG) within the framework of the strong-field approximation (SFA), which clearly separates the nonadiabatic contribution from the adiabatic one. At the single-atom response level, we show that the nonadiabatic phase leads to a significant shift in the photon energy corresponding to the peak of the HHG spectrum, a phenomenon that can be attributed to the interference of different quantum trajectories. The analytical expression for the nonadiabatic phase also provides further theoretical support for reconstructing electron dynamics (excursion time) from HHG spectra generated using mixed gases. At the macroscopic level, our approach yields a fully analytical nonadiabatic expression for atomic dipole phase matching, which can accurately predict the HHG phase-matching condition and shows good agreement with both experiments and numerical SFA simulations. In particular, this expression explicitly reveals how the HHG phase depends on laser and atomic parameters. This may enable more convenient control of the HHG phase by adjusting laser parameters in future experiments aimed at attosecond pulse generation and the development of coherent high energy light sources.

  PublisherDOI

• Supplementary document for Analytical description of phase in high-order harmonic generation: nonadiabatic effect on single atom response and macroscopic phase matching - 7853375.pdf

  Figshare · 2026-04-06

  articleOpen access

  Supplemental Document

  PublisherDOI

• Analytical description of phase in high-order harmonic generation: nonadiabatic effect on single atom response and macroscopic phase matching

  Figshare · 2026-04-06

  otherOpen access

  We propose a fully analytical expression for the phase of high-order harmonic generation (HHG) within the framework of the strong-field approximation (SFA), which clearly separates the nonadiabatic contribution from the adiabatic one. At the single-atom response level, we show that the nonadiabatic phase leads to a significant shift in the photon energy corresponding to the peak of the HHG spectrum, a phenomenon that can be attributed to the interference of different quantum trajectories. The analytical expression for the nonadiabatic phase also provides further theoretical support for reconstructing electron dynamics (excursion time) from HHG spectra generated using mixed gases. At the macroscopic level, our approach yields a fully analytical nonadiabatic expression for atomic dipole phase matching, which can accurately predict the HHG phase-matching condition and shows good agreement with both experiments and numerical SFA simulations. In particular, this expression explicitly reveals how the HHG phase depends on laser and atomic parameters. This may enable more convenient control of the HHG phase by adjusting laser parameters in future experiments aimed at attosecond pulse generation and the development of coherent high energy light sources.

  PublisherDOI

Recent grants

• Strong Field Physics with A Twist

  NSF · $200k · 2022–2026

Frequent coauthors

• Lisa Ortmann

  The Ohio State University

  46 shared

• S. Cohen

  Princeton Plasma Physics Laboratory

  46 shared

• A. H. Glasser

  Fusion Academy

  41 shared

• C. Brunkhorst

  36 shared

• D. R. Welch

  36 shared

• Maciej Lewenstein

  Institute of Photonic Sciences

  35 shared

• U. Keller

  ETH Zurich

  31 shared

• Alexis Chacón

  30 shared