Signature of an ultrafast photoinduced Lifshitz transition in the nodal-line semimetal ZrSiTe

Abstract

Here we report an ultrafast optical spectroscopic study of the nodal-line semimetal ZrSiTe. Our measurements reveal that, converse to other compounds of the family, the sudden injection of electronic excitations results in a strongly coherent response of an A 1g phonon mode that dynamically modifies the distance between Zr and Te atoms and Si layers. "Frozen phonon" density functional theory calculations, in which band structures are calculated as a function of nuclear position along the phonon mode coordinate, show that large displacements along this mode alter the material's electronic structure significantly, forcing bands to approach and even cross the Fermi energy. The incoherent part of the time-domain response reveals that a delayed electronic response at low fluence discontinuously evolves into an instantaneous one for excitation densities larger than 3.43 × 10 17 cm −3 . This sudden change of the dissipative channels for electronic excitations is indicative of an ultrafast Lifshitz transition, which we tentatively associate with a change in topology of the Fermi surface driven by a symmetry-preserving A 1g phonon mode.

Square-Net Topological Semimetals: How Spectroscopy Furthers Understanding and Control

“…We showed that a similar coherent A 1g phonon mode might be capable of dynamically modulating the band structure of ZrSiTe . Exciting at 0.95 and 1.24 eV, in the NIR, we observed large coherent phononswith amplitudes of tens of percent of the total signal in the first couple periodsat both pump energies and at all fluences studied (Figure a).…”

NMR determination of Van Hove singularity and Lifshitz transitions in the nodal-line semimetal ZrSiTe

“…In Zr-SiSe, transport results were recently proposed to give evidence for even larger T -induced changes of μ [15]. For the present case, we assume relative shifts of band energies contribute to this process causing the node to shift relative to μ, perhaps induced by the promotion of carriers from donor states, in a manner akin to the changes that have been proposed [17] to accompany the optical promotion of carriers in ZrSiTe.…”

“…Its large region of topologically protected drumhead surface states [13] as well as very large spin Berry curvature and associated spin Hall and Nernst response [14] suggest spintronic and related applications. Suggested changes of Fermi surface topology in this family include a temperature-induced Lifshitz transition in ZrSiSe [15], and a pressure-induced Lifshitz transition in ZrSiTe [16] as well as indications of a photoinduced phonon driven transformation [17].…”

“…The sharp VHS adjacent to the protected nodal line implies that additional electronic features relying upon the enhanced g(E ) could be engineered into this system [26][27][28][29][30], by tuning E F to the VHS. Tuning could be accomplished by chemical pressure [43], physical pressure or strain [16,44], and light activation [17] with the required energy difference being quite small. This could be another avenue for switching the topological behavior for quantum computing applications.…”

Exceptional hexagonal warping effect in multi-Weyl semimetals

“…At the same time, quantum systems with light tuned properties are a fascinating topic of current interest [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48]. The light induced modifications of topological properties have led to the uncovering of various phenomena, which can cause important changes in the Fermi surface topology [29,49,50]. Recently, it has been shown that application of light can change the positions of the EPs in NH systems [29,50].…”