Photoinduced Dirac semimetal in ZrTe5

Abstract

Novel phases of matter with unique properties that emerge from quantum and topological protection present an important thrust of modern research. Of particular interest is to engineer these phases on demand using ultrafast external stimuli, such as photoexcitation, which offers prospects of their integration into future devices compatible with optical communication and information technology. Here, we use MeV Ultrafast Electron Diffraction (UED) to show how a transient three-dimensional (3D) Dirac semimetal state can be induced by a femtosecond laser pulse in a topological insulator ZrTe${}_5$. We observe marked changes in Bragg diffraction, which are characteristic of bond distortions in the photoinduced state. Using the atomic positions refined from the UED, we perform density functional theory (DFT) analysis of the electronic band structure. Our results reveal that the equilibrium state of ZrTe${}_5$ is a topological insulator with a small band gap of $\sim$25 meV, consistent with angle-resolved photoemission (ARPES) experiments. However, the gap is closed in the presence of strong spin-orbit coupling (SOC) in the photoinduced transient state, where massless Dirac fermions emerge in the chiral band structure. The time scale of the relaxation dynamics to the transient Dirac semimetal state is remarkably long, $\tau \sim$160 ps, which is two orders of magnitude longer than the conventional phonon-driven structural relaxation. The long relaxation is consistent with the vanishing density of states in Dirac spectrum and slow spin-repolarization of the SOC-controlled band structure accompanying the emergence of Dirac fermions.

arXiv comment19 pages, 4 figures plus 7 Supplementary pages, 5 Supplementary figures

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Cited by in corpus (11)

• One-Dimensional van der Waals Quantum Materials -- State of the Art and Perspectives
• Topological phase transition and phonon-space Dirac topology surfaces in ZrTe${}_5$
• Band Structure Driven Thermoelectric Response of Topological Semiconductor ZrTe${}_5$
• Robust and tunable Weyl phases by coherent infrared phonons in ZrTe${}_5$
• Revealing temperature evolution of the Dirac band in ZrTe${}_5$ via magneto-infrared spectroscopy
• Revealing the band structure of ZrTe${}_5$ using Multicarrier Transport
• Signature of pressure-induced topological phase transition in ZrTe${}_5$
• Optical manipulation of the topological phase in ZrTe5 revealed by time- and angle-resolved photoemission
• First-principles studies of fermiology in topological phases of bulk ZrTe${}_5$
• Magnetic Brightening and Nanoscale Imaging of Spin-Polarized Helical Edge Modes
• Research on topological materials using ultrafast spectroscopy