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Field-driven attosecond charge dynamics in germanium

Nature Photonics volume 17, pages 1059–1065 (2023)Cite this article

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Abstract

The possibility to excite and control charges in matter on ultrafast timescales is a key requisite to overcome the current limits of information transfer and data processing. The major route towards this milestone is based on the employment of short light pulses to manipulate the electro-optical properties of a solid. Nevertheless, the elusive physical mechanisms that unfold on extreme timescales are often complex and entangled, hindering their correct identification and possible exploitation. Here we investigate light-driven excitation in monocrystalline germanium by using attosecond transient reflection spectroscopy. We show that the complex regime established during light–matter interaction cannot be treated with simplified models but requires a detailed analysis in time and reciprocal space to address diverse phenomena such as tunnelling, band dressing, intra-band motion and multiphoton injection. Although single-photon absorption activates and develops earlier during excitation, two-photon processes, tunnelling and other field-driven phenomena reach their maximum effect soon after the peak of the pump pulse. Going against past observations, our results suggest that field-driven phenomena—namely intra-band transitions—can hinder charge injection, confirming that it is impossible to establish the next generation of petahertz information technology without a deep understanding of the diverse physical mechanism behind light–matter interaction.

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Fig. 1: Experimental scheme and static properties of germanium.
Fig. 2: Attosecond transient reflectivity measurement in germanium.
Fig. 3: Time-dependent excited electron population in reciprocal space.
Fig. 4: Intensity dependence of the photoinjection process.

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Data availability

The data generated and analysed in this study are provided in the Supplementary Information and/or Source Data. Extended data were available from the corresponding author on reasonable request. Source Data are provided with this paper.

Code availability

All the custom codes used in this study are available from the corresponding author on reasonable request.

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Acknowledgements

This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 848411 title AuDACE), from MIUR PRIN aSTAR (grant no. 2017RKWTMY) and Laserlab-Europe EU-H2020 GA no. 871124.

Author information

Authors and Affiliations

  1. Department of Physics, Politecnico di Milano, Milan, Italy

    Giacomo Inzani, Nicola Di Palo, Gian Luca Dolso, Bruno Moio, Mauro Nisoli & Matteo Lucchini

  2. CNR—Istituto Nanoscienze, Modena, Italy

    Lyudmyla Adamska, Stefano Pittalis & Carlo Andrea Rozzi

  3. Dipartimento di Fisica ‘E. R. Caianiello’, Università degli Studi di Salerno, Fisciano, Italy

    Amir Eskandari-asl, Luciano Jacopo D’Onofrio & Adolfo Avella

  4. CNR-IMM, Unit of Agrate Brianza, Agrate Brianza, Italy

    Alessio Lamperti & Alessandro Molle

  5. Institute for Photonics and Nanotechnologies, IFN-CNR, Milan, Italy

    Rocío Borrego-Varillas, Mauro Nisoli & Matteo Lucchini

  6. CNR-SPIN, UoS di Salerno, Fisciano, Italy

    Adolfo Avella

  7. Unità CNISM di Salerno, Università degli Studi di Salerno, Fisciano, Italy

    Adolfo Avella

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  1. Giacomo Inzani
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Contributions

G.I, L.A. and A.E. contributed equally to this work. M.L., M.N. and R.B.-V. conceived the experiment. G.I, N.D.P, G.L.D. and B.M. performed the measurements and contributed to the definition of the experimental procedures. G.I. evaluated and analysed the results, calculated the sample absorption and estimated the experimental excited electron density. A.L. and A.M. provided the samples. L.A., S.P. and C.A.R. designed, performed and analysed DFT and TDDFT simulations. L.J.D'O. and A.A. performed initial DFT calculations. A.E.-a. and A.A. developed DPOA, computed the dynamical bands and evaluated the inter/intra-band contributions. L.D. and A.E. computed electron populations in DPOA. All authors participated in the scientific discussion. G.I. and M.L. wrote the first version of the paper to which all authors contributed.

Corresponding authors

Correspondence to Carlo Andrea Rozzi, Adolfo Avella or Matteo Lucchini.

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Nature Photonics thanks Michael Zuerch, Vladislav Yakovlev and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–22, Discussion and Table 1.

Supplementary Video 1

Time-dependent 3D representation in the reciprocal space of the number of excited electrons.

Supplementary Video 2

Time-dependent evolution of the pumped band structure.

Source data

Source Data Fig. 1–4

Source data of Fig. 1–4

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Inzani, G., Adamska, L., Eskandari-asl, A. et al. Field-driven attosecond charge dynamics in germanium. Nat. Photon. 17, 1059–1065 (2023). https://doi.org/10.1038/s41566-023-01274-1

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