Symmetries and Topology in Nonlinear Ultrafast Optical Spectroscopy in Solids and Quantum Materials

Dear Colleagues,

The ‘spin-conductivity feature’ at the topological surface state (TSS) or edge states and the insulating character inside the 2D and 3D topological insulators (TIs) of Bi2Se3 (3D-TI) promise a robust platform for optimizing classical devices toward a new era of quantum information, valley spintronics information and, thus, quantum electronic devices, i.e., quantum computers. However, the characterization of electron structures and ultrafast control of electrons at the natural time scale (10^-18 s = 1 as) remains a challenge in those quantum materials (QMs).

In the light of these phenomena and their relevance, we wish to encourage our colleagues from the ultrafast sciences and condensed matter physics (CMP) communities to join efforts with the vision of establishing a Special Issue (SI) on the emerging field of “Symmetries and Topological Nonlinear Optical Ultrafast-Spectroscopy of Quantum Materials and Solids (SNOU-QMS)”. The cornerstone questions and curiosities for several experts around the world are: (1) How can we extend ultrafast physics tools, such as the high-order harmonic generation (HHG) process, to explore new avenues in CMP? (2) How can we detect and manipulate topological insulators (TIs), topological orders, Weyl semimetals (WDSMs), quantum spin liquid phases (QSLs)—basically speaking, quantum materials—with lasers?

In essence, how and why can ultrafast science, via HHG, now have a strong positive impact on CMP?

In simple words, the high-harmonic generation (HHG) is a natural process described by (1) right after a solid or nontrivial topological insulator subjected to a strong middle infrared laser, (2) the basic polarizations of and currents of the medium emit a totally new highly energetic photon spectrum with respect to the fundamental energy of the laser-photon. Topological materials have shown impressive sensitivity to the HHG process and the symmetries of Hamiltonian materials, though the above question still remains unclear, with the aim of featuring TIs or QMs.

As these fundamental questions are emerging nowadays, numerous papers have been published in Nature, Nature Photonics, Physical Review Lett., ACS Nano Lett., among others, with the interpretation that the HHG can fundamentally be an experimental observable for the topological characterization of TIs. However, there are many practical controversies, both experimentally and theoretically, which still question the HHG aspects in fully characterizing QMs: In particular, how to detect topological phase transitions in TIs and Chern insulators with their protected topological invariants of the Z2 and Chern number, respectively?

For instance:

[1] D. Bauer and K. Hansen. High-harmonic generation in solids with and without topological edge states. Phys. Rev. Lett. 120 no. 6, p. 177 401 (2018).

[2] R. E. F. Silva et al. Topological strong-field physics on sub-laser-cycle timescale. Nature Photonics URL https://doi.org/10.1038/s41566-019-0516-1.

[3] J. W. McIver et al. Light-induced anomalous hall effect in graphene. Nature Phys. 41 no. 16, pp. 38–41 (2020).

[4] A. Chacon et al. Circular dichroism in a higher-order harmonic generation: Heralding topological phases and transitions in Chern insulators. Phys. Rev. B 102, p. 134 115 (2020). URL https://link.aps.org/doi/10.1103/PhysRevB.102.134115.

[5] C. P. Schmid, L. Weigl, P. Grössing, V. Junk, C. Gorini, S. Schlauderer, S. Ito, M. Meierhofer, N. Hofmann, D. Afanasiev, J. Crewse, K. A. Kokh, O. E. Tereshchenko, J. Güdde, F. Evers, J. Wilhelm, K. Richter, U. Höfer & R. Huber. Tunable non-integer high-harmonic generation in a topological insulator. Nature 598, 395 (2021).

[6] Yong Sing You, Mengxi Wu, Yanchun Yin, Andrew Chew, Xiaoming Ren, Shima Gholam-Mirzaei, Dana A.Browne, Michael Chini, Zenghu Chang, Kenneth J. Schafer, Mette B. Gaarde, and Shambhu Ghimire. Laser waveform control of extreme ultraviolet high harmonics from solids. Optics Lett. 42, 1816 (2017).

[7] Yong Sing You, Yanchun Yin, Yi Wu, Andrew Chew, Xiaoming Ren, Fengjiang Zhuang, Shima Gholam-Mirzaei, Michael Chini, Zenghu Chang & Shambhu Ghimire. High-harmonic generation in amorphous solids. Nature Comm. 8:724 (2017) DOI: 10.1038/s41467-017-00989-4.

[8] Baykusheva, Denitsa, Chacon, Alexis and Kim, Dasol and Kim, Dong Eon and Reis, David A. and Ghimire, Shambhu. Strong-field physics in three-dimensional topological insulators. Phys. Rev. A 103, 023101 (2021). https://link.aps.org/doi/10.1103/PhysRevA.103.023101

[9] Baykusheva, Denitsa and Chacon, Alexis and Lu, Jian and Bailey, Trevor P. and Sobota, Jonathan A. and Soifer, Hadas and Kirchmann, Patrick S. and Rotundu, Costel and Uher, Ctirad and Heinz, Tony F. and Reis, David A. and Ghimire, Shambhu. All-Optical Probe of Three-Dimensional Topological Insulators Based on High-Harmonic Generation by Circularly Polarized Laser Fields. ACS Nano Lett. Oct 22nd (2021) https://doi.org/10.1021/acs.nanolett.1c02145

Finally, I invite you to submit and join efforts toward an approximated answer to the above challenging questions.

Prof. Dr. Alexis Chacón
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Symmetry is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• Topology
• Geometrical phase or topological invariant
• Quantum materials
• Controversies in nonlinear optical spectroscopy