Coherent optical phonon oscillation and possible electronic softening in WTe2 crystals

He, Bin; Zhang, Chunfeng; Zhu, Weida; Li, Yufeng; Liu, Shenghua; Zhu, Xiyu; Wu, Xiaohu; Wang, Xiaoyong; Wen, Hao

doi:10.1038/srep30487

Cited by 38 publications

(38 citation statements)

References 64 publications

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“…38 WTe 2 , a type-II Weyl semimetal, is similar: in samples with a momentum gap at E F , ∆R(t) decays in two parts, with τ B = 5 to 15 ps. 56,57 In contrast, the linear, Dirac-like dispersion in our materials speeds recombination because it enables low-momentum transitions between electron and hole states. The linear dispersion also ensures that Auger processes (both interband and intraband) automatically satisfy both energy and momentum conservation, provided they occur along a straight line in momentumspace.…”

Section: Discussionmentioning

confidence: 97%

Similar ultrafast dynamics of several dissimilar Dirac and Weyl semimetals

Weber

Berggren

Masten

et al. 2017

Journal of Applied Physics

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Recent years have seen the rapid discovery of solids whose low-energy electrons have a massless, linear dispersion, such as Weyl, line-node, and Dirac semimetals. The remarkable optical properties predicted in these materials show their versatile potential for optoelectronic uses. However, little is known of their response in the picoseconds after absorbing a photon. Here we measure the ultrafast dynamics of four materials that share non-trivial band structure topology but that differ chemically, structurally, and in their low-energy band structures: ZrSiS, which hosts a Dirac line node and Dirac points; TaAs and NbP, which are Weyl semimetals; and Sr 1−y Mn 1−z Sb 2 , in which Dirac fermions coexist with broken time-reversal symmetry. After photoexcitation by a short pulse, all four relax in two stages, first sub-picosecond, and then few-picosecond. Their rapid relaxation suggests that these and related materials may be suited for optical switches and fast infrared detectors. The complex change of refractive index shows that photoexcited carrier populations persist for a few picoseconds.

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Section: Discussionmentioning

confidence: 97%

Similar ultrafast dynamics of several dissimilar Dirac and Weyl semimetals

Weber

Berggren

Masten

et al. 2017

Journal of Applied Physics

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“…Photoinduced structural phase transitions have been found in some other compounds [24,36,37], but the mechanisms of the transition remain debated. Another possibility is the thermal effect in the lattice temperature induced by the intense pump [38,39]. In the latter case, the expected temperature rise ΔT at temperature (T 0 ) can be estimated by the equation Sδρ=M…”

Section: Ultrafast Coherent Phonon Spectroscopymentioning

confidence: 99%

Light-Induced Subpicosecond Lattice Symmetry Switch in MoTe2

Zhang¹,

Wang²,

Li³

et al. 2019

Phys. Rev. X

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The recent development of ultrashort laser pulses allows for optical control of structural and electronic properties of complex quantum materials. The layered transition-metal dichalcogenide MoTe 2 , which can crystallize into several different structures with distinct topological and electronic properties, provides possibilities to control or switch between different phases. In this study, we report a photoinduced subpicosecond structural transition between the type-II Weyl semimetal phase and normal-semimetal phase in bulk crystalline MoTe 2 by using ultrafast pump-probe and time-resolved second-harmonic-generation spectroscopy. The phase transition is most clearly characterized by the dramatic change of the shear oscillation mode and the intensity loss of second-harmonic generation. This work opens up new possibilities for ultrafast manipulation of the topological properties of solids, enabling potentially practical applications for a topological switch device with ultrafast excitations.

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“…Strong mode-specific excitation of specific atomic vibrations (phonon modes) in solids [1] has been shown [2][3][4][5][6] to drive drastic changes in collective electronic properties. Of the many effects observed, perhaps the most dramatic is the superconducting-like behavior observed at temperatures far above the equilibrium transition temperature in strongly irradiated YBa 2 Cu 3 O 6+x [7] and K 3 C 60 [2].…”

mentioning

confidence: 99%

Transient superconductivity from electronic squeezing of optically pumped phonons

et al. 2017

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Advances in light sources and time resolved spectroscopy have made it possible to excite specific atomic vibrations in solids and to observe the resulting changes in electronic properties but the mechanism by which phonon excitation causes qualitative changes in electronic properties, has remained unclear. Here we show that the dominant symmetry-allowed coupling between electron density and dipole active modes implies an electron density-dependent squeezing of the phonon state which provides an attractive contribution to the electron-electron interaction, independent of the sign of the bare electron-phonon coupling and with a magnitude proportional to the degree of laser-induced phonon excitation. Reasonable excitation amplitudes lead to non-negligible attractive interactions that may cause significant transient changes in electronic properties including superconductivity. The mechanism is generically applicable to a wide range of systems, offering a promising route to manipulating and controlling electronic phase behavior in novel materials. * These two authors contributed equally 1 arXiv:1609.03802v2 [cond-mat.supr-con] May 2017Strong mode-specific excitation of specific atomic vibrations (phonon modes) in solids [1] has been shown [2-6] to drive drastic changes in collective electronic properties. Of the many effects observed, perhaps the most dramatic is the superconducting-like behavior observed at temperatures far above the equilibrium transition temperature in strongly irradiated YBa 2 Cu 3 O 6+x [7] and K 3 C 60 [2]. Because optically addressable phonon modes are dipole active (odd parity) zone center vibrations which typically do not couple linearly to local electronic quantities such as the density or orbital occupancy, the mechanism by which phonon excitation changes electronic properties has not been clear, although many interesting proposals have been made [9][10][11][12][13][14]. Here we present a new and general mechanism that naturally explains how optical phonon excitation can lead to changes in electronic properties. The key idea is that the dominant symmetry-allowed coupling between electron density and dipole active modes is quadratic, implying an electron density-dependent squeezing of the phonon state. We show that this electron density dependence of the phonon squeezing provides a sizable attractive contribution to the electron-electron interaction. The attractive contribution is independent of the sign of the bare electron-phonon coupling, has a magnitude proportional to the degree of laser-induced phonon excitation, and is large enough that reasonable values of the excitation amplitude lead to non-negligible attractive interactions.The mechanism is generically applicable to a wide range of systems, offering a promising route to manipulating and controlling electronic phase behavior.To demonstrate the mechanism we consider a minimal tight-binding model of electrons that can hop between sites of a lattice, are subject to electronic interactions, and are coupled quadratically to ...

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Coherent optical phonon oscillation and possible electronic softening in WTe2 crystals

Cited by 38 publications

References 64 publications

Similar ultrafast dynamics of several dissimilar Dirac and Weyl semimetals

Similar ultrafast dynamics of several dissimilar Dirac and Weyl semimetals

Light-Induced Subpicosecond Lattice Symmetry Switch in MoTe2

Transient superconductivity from electronic squeezing of optically pumped phonons

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