Terahertz-driven phonon upconversion in SrTiO3

Kozina, Michael; Fechner, Michael; Maršík, Přemysl; Driel, Tim van; Glownia, James M.; Bernhard, C.; Radović, M.; Zhu, Diling; Bonetti, Stefano; Staub, U.; Hoffmann, Matthias C.

doi:10.1038/s41567-018-0408-1

Cited by 165 publications

(134 citation statements)

References 72 publications

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“…While it has been shown that parametric resonances of phonons may influence the superconducting critical temperature [73], the mechanism here is fundamentally different from the parametric amplification of light by an optically excited Higgs mode in superconductors discovered recently [21]. We further note that coherent energy transfer to a nearly silent phonon mode has been observed in a high-harmonic phonon upconversion process [43].…”

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confidence: 54%

Parametric Excitation of an Optically Silent Goldstone-Like Phonon Mode

2020

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It has recently been indicated that the hexagonal manganites exhibit Higgs-and Goldstone-like phonon modes that modulate the amplitude and phase of their primary order parameter. Here, we describe a mechanism by which a silent Goldstone-like phonon mode can be coherently excited, which is based on nonlinear coupling to an infrared-active Higgs-like phonon mode. Using a combination of first-principles calculations and phenomenological modeling, we describe the coupled Higgs-Goldstone dynamics in response to the excitation with a terahertz pulse. Besides theoretically demonstrating coherent control of crystallographic Higgs and Goldstone excitations, we show that the previously inaccessible silent phonon modes can be excited coherently with this mechanism.Order parameters are physical observables that are used to quantify the different states of matter. Their amplitudes and phases can be excited by external stimuli, such as a laser pulse, leading to exotic states of matter that cannot be accessed in equilibrium [1]. Two particular excitations are Higgs and Goldstone modes, which correspond to the modulation of the amplitude and phase of an order parameter that breaks a continuous symmetry. Originally discussed in the context of particle physics [2] and superconductivity [3], Higgs and Goldstone excitations were found in cold atom systems, such as superfluids [4][5][6][7][8] or supersolids [9]. Higgs and Goldstone modes are well-studied in superconductors today [10][11][12][13][14][15][16][17][18][19][20][21], and similar manifestations have recently been reported in charge density wave (CDW) systems [22][23][24], antiferromagnets [25][26][27], and excitonic insulators [28]. It has been debated whether the optical and acoustic vibrational modes of solids can be considered Higgs and Goldstone excitations of the crystal lattice [29]. Several complex transition metal oxide compounds have shown signatures of optical Goldstone-like phonon modes that live in their symmetry-broken potential energy landscape [30][31][32][33][34].Coherent control over Raman-active phonons via impulsive stimulated Raman scattering using visible light pulses is well-established [35,36]. Recently, the excitation of infrared (IR)-active phonons with large amplitudes via IR absorption has become feasible through the development of high intensity terahertz and mid-IR sources. This progress has enabled selective control over the dynamics of the crystal lattice through nonlinear phonon interactions using ionic Raman scattering [37-39] and two-particle absorption mechanisms [40][41][42][43][44][45]. In contrast, phonon modes that do not respond to IR absorption or Raman scattering techniques, so called silent modes, can only be detected through hyper-Raman scattering. As hyper-Raman scattering is a third-order interaction of the electric field component of light with a * djuraschek@seas.harvard.edu † prineha@seas.harvard.edu phonon mode, it is inefficient and no coherent excitation has been achieved yet. Higgs and Goldstone modes, similar to silent p...

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confidence: 54%

Parametric Excitation of an Optically Silent Goldstone-Like Phonon Mode

2020

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“…This effect of coherent phonons is in stark contrast to that of incoherent phonons from thermal excitations, which diminishes topological enhancement of surface transport via random lattice scattering, heating, surface-bulk charge transfer and coupling. Ultrafast phononics has been explored as a new avenue to manipulate properties of superconductors, 8 oxides, 9,10 semimetal 11 and photovoltaic semiconductors. 12 Although experimental realizations of coherent phonon generation have been explored in TIs, 7,13,14 the influence of such vibrational coherence on the surface helical transport has not been observed until now.…”

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confidence: 99%

Light control of surface–bulk coupling by terahertz vibrational coherence in a topological insulator

et al. 2020

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The demand for disorder-tolerant quantum logic and spin electronics can be met by generating and controlling dissipationless spin currents protected by topology. Dirac fermions with helical spin-locking surface transport offer a way of achieving such a goal. Yet, surface-bulk coupling can lead to strong Dirac electron scattering with bulk carriers and phonons as well as impurities, assisted by such dissipative channel, which results in "topological breakdown". Here, we demonstrate that coherent lattice vibrations periodically driven by a single-cycle terahertz (THz) pulse can significantly suppress such dissipative channel in topological insulators. This is achieved by reducing the phase space in the bulk available for Dirac fermion scattering into during coherent lattice oscillations in Bi 2 Se 3 . This light-induced suppression manifests as a remarkable transition exclusively in surface transport, absent for bulk, above the THz electric fields for driving coherent phonons, which prolongs the surface transport lifetime. These results, together with simulations, identify the critical role of spin-orbit coupling for the "phase space contraction" mechanism that suppresses the surface-bulk coupling. Imposing vibrational quantum coherence into topological states of matter may become a universal light control principle for reinforcing the symmetry-protected helical transport.npj Quantum Materials (2020) 5:13 ; https://doi.

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“…The terahertz (THz) frequency range lies in the microwave and infrared wavelength ranges of the electromagnetic spectrum, showing potential applications in the practical fields of spectral analysis, imaging, homeland security detection, and high-speed wireless communication (in the range of several hundred Gbit s −1 ) [1][2][3][4][5][6][7][8]. But to further substantial development of THz science and technology, there is a high demand for well-performing functional waveguide devices and components.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Phonon Scattering on the Tunable Mechanisms of Terahertz Graphene Metamaterials

Lin

Liu

et al. 2019

Nanomaterials

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The influences of different kinds of phonon scatterings (i.e., acoustic (AC) phonon, impurity, and longitudinal optical (LO) phonon scatterings) on the tunable propagation properties of graphene metamaterials structures have been investigated, also including the effects of graphene pattern structures, Fermi levels, and operation frequencies. The results manifested that, at room temperature, AC phonon scattering dominated, while with the increase in temperature, the LO phonon scattering increased significantly and played a dominate role if temperature goes beyond 600 K. Due to the phonon scatterings, the resonant properties of the graphene metamaterial structure indicated an optimum value (about 0.5–0.8 eV) with the increase in Fermi level, which were different from the existing results. The results are very helpful to understand the tunable mechanisms of graphene functional devices, sensors, modulators, and antennas.

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Terahertz-driven phonon upconversion in SrTiO3

Cited by 165 publications

References 72 publications

Parametric Excitation of an Optically Silent Goldstone-Like Phonon Mode

Parametric Excitation of an Optically Silent Goldstone-Like Phonon Mode

Light control of surface–bulk coupling by terahertz vibrational coherence in a topological insulator

Investigation of Phonon Scattering on the Tunable Mechanisms of Terahertz Graphene Metamaterials

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