Stanford Advisors

Current Research and Scholarly Interests

My current research focuses on light-matter interactions on extremely fast time scales (femto- and attoseconds). This includes ultrafast current injection and the generation of high harmonics in two-dimensional materials like TMDCs and layered heterostructures.

All Publications

  • High-harmonic generation from artificially stacked 2D crystals NANOPHOTONICS Heide, C., Kobayashi, Y., Johnson, A. C., Heinz, T. F., Reis, D. A., Liu, F., Ghimire, S. 2023
  • Floquet engineering of strongly driven excitons in monolayer tungsten disulfide NATURE PHYSICS Kobayashi, Y., Heide, C., Johnson, A. C., Tiwari, V., Liu, F., Reis, D. A., Heinz, T. F., Ghimire, S. 2023
  • Intense infrared lasers for strong-field science ADVANCES IN OPTICS AND PHOTONICS Chang, Z., Fang, L., Fedorov, V., Geiger, C., Ghimire, S., Heide, C., Ishii, N., Itatani, J., Joshi, C., Kobayashi, Y., Kumar, P., Marra, A., Mirov, S., Petrushina, I., Polyanskiy, M., Reis, D. A., Tochitsky, S., Vasilyev, S., Wang, L., Wu, Y., Zhou, F. 2022; 14 (4): 652-782

    View details for DOI 10.1364/AOP.454797

    View details for Web of Science ID 000917420400001

  • In-Situ Nanoscale Focusing of Extreme Ultraviolet Solid-State High Harmonics PHYSICAL REVIEW X Korobenko, A., Rashid, S., Heide, C., Naumov, A., Reis, D. A., Berini, P., Corkum, P. B., Vampa, G. 2022; 12 (4)
  • Probing topological phase transitions using high-harmonic generation NATURE PHOTONICS Heide, C., Kobayashi, Y., Baykusheva, D. R., Jain, D., Sobota, J. A., Hashimoto, M., Kirchmann, P. S., Oh, S., Heinz, T. F., Reis, D. A., Ghimire, S. 2022
  • Probing electron-hole coherence in strongly driven 2D materials using high-harmonic generation OPTICA Heide, C., Kobayashi, Y., Johnson, A. C., Liu, F., Heinz, T. F., Reis, D. A., Ghimire, S. 2022; 9 (5): 512-516
  • Light-field control of real and virtual charge carriers. Nature Boolakee, T., Heide, C., Garzon-Ramirez, A., Weber, H. B., Franco, I., Hommelhoff, P. 2022; 605 (7909): 251-255


    Light-driven electronic excitation is a cornerstone for energy and information transfer. In the interaction of intense and ultrafast light fields with solids, electrons may be excited irreversibly, or transiently during illumination only. As the transient electron population cannot be observed after the light pulse is gone, it is referred to as virtual, whereas the population that remains excited is called real1-4. Virtual charge carriers have recently been associated with high-harmonic generation and transient absorption5-8, but photocurrent generation may stem from real as well as virtual charge carriers9-14. However, a link between the generation of thecarrier types and their importance for observables of technological relevance is missing. Here we show that real and virtual charge carriers can be excited and disentangled in the optical generation of currents in a gold-graphene-gold heterostructure using few-cycle laser pulses. Depending on the waveform used for photoexcitation, real carriers receive net momentum and propagate to the gold electrodes, whereas virtual carriers generate a polarization response read out at the gold-graphene interfaces. On the basis of these insights, we further demonstrate a proof of concept of a logic gate for future lightwave electronics. Our results offer a direct means to monitor and excite real and virtual charge carriers. Individual control over each type of carrier will markedly increase the integrated-circuit design space and bring petahertz signal processing closer to reality15,16.

    View details for DOI 10.1038/s41586-022-04565-9

    View details for PubMedID 35546189

  • Electronic Coherence and Coherent Dephasing in the Optical Control of Electrons in Graphene. Nano letters Heide, C., Eckstein, T., Boolakee, T., Gerner, C., Weber, H. B., Franco, I., Hommelhoff, P. 2021


    Electronic coherence is of utmost importance for the access and control of quantum-mechanical solid-state properties. Using a purely electronic observable, the photocurrent, we measure a lower bound of the electronic coherence time of 22 ± 4 fs in graphene. The photocurrent is ideally suited to measure electronic coherence, as it is a direct result of coherent quantum-path interference, controlled by the delay between two ultrashort two-color laser pulses. The maximum delay for which interference between the population amplitude injected by the first pulse interferes with that generated by the second pulse determines the electronic coherence time. In particular, numerical simulations reveal that the experimental data yields a lower bound on the electronic coherence time, masked by coherent dephasing due to the broadband absorption in graphene. We expect that our results will significantly advance the understanding of coherent quantum control in solid-state systems ranging from excitation with weak fields to strongly driven systems.

    View details for DOI 10.1021/acs.nanolett.1c02538

    View details for PubMedID 34735774

  • Optical current generation in graphene: CEP control vs. omega + 2 omega control NANOPHOTONICS Heide, C., Boolakee, T., Eckstein, T., Hommelhoff, P. 2021; 10 (14): 3701-3707
  • Light field-driven electron dynamics in 2D-materials Boolakee, T., Heide, C., Weber, H. B., Hommelhoff, P., IEEE IEEE. 2021
  • The effect of photo-carrier doping on the generation of high harmonics from MoS2 Heide, C., Kobayashi, Y., Liu, F., Ghimire, S., Heinz, T. F., Reis, D. A., IEEE IEEE. 2021