Laser-induced phonon-phonon interactions in bismuth

Zijlstra, Eeuwe S.; Tatarinova, Larisa L.; Garcia, Martín E.

doi:10.1103/physrevb.74.220301

Cited by 94 publications

(86 citation statements)

References 21 publications

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“…This motion can be tracked in the time domain by measuring the effects of the coherent phonons on the transient reflectivity of a material and has been used extensively as a probe to study the lattice in near-equilibrium conditions in the vicinity of phase transitions 11 , as well as to look at phonon softening [12][13][14] and hardening 15 when the system is strongly driven. Phonon softening or hardening results from a change in the curvature 16,17 of the lattice potential, but not from a change in the symmetry of the potential. When the symmetry changes, the number of modes typically changes, which may occur when a soft phonon mode tends to zero frequency for a second-order phase transition 14 or may be step-like for a first-order phase transition.…”

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confidence: 99%

Ultrafast changes in lattice symmetry probed by coherent phonons

et al. 2012

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The electronic and structural properties of a material are strongly determined by its symmetry. Changing the symmetry via a photoinduced phase transition offers new ways to manipulate material properties on ultrafast timescales. However, to identify when and how fast these phase transitions occur, methods that can probe the symmetry change in the time domain are required. Here we show that a time-dependent change in the coherent phonon spectrum can probe a change in symmetry of the lattice potential, thus providing an all-optical probe of structural transitions. We examine the photoinduced structural phase transition in Vo 2 and show that, above the phase transition threshold, photoexcitation completely changes the lattice potential on an ultrafast timescale. The loss of the equilibrium-phase phonon modes occurs promptly, indicating a non-thermal pathway for the photoinduced phase transition, where a strong perturbation to the lattice potential changes its symmetry before ionic rearrangement has occurred.

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confidence: 99%

Ultrafast changes in lattice symmetry probed by coherent phonons

et al. 2012

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“…2). In contrast, Zijlstra et al 34 performed frozen phonon calculations on the zone-center mode, also assuming rapid scattering and equilibration throughout all conduction and valence bands, but using a single chemical potential, in which the carrier density is determined solely by the temperature of the electron-hole plasma. Johnson et al 29 performed depth resolved femtosecond x-ray diffraction to measure the phonon dynamics and concluded that the two-chemical potential model may be appropriate only on a time-scale less than a single phonon period, transitioning a single chemical potential model.…”

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confidence: 99%

“…36 may call into question the detailed quantitative conclusions of analyses (including those of Refs. 26,27,30,31,34,35) that have assumed insignificant heat transfer from the electron-hole plasma to the lattice vibration modes in the first few picoseconds following photo-excitation.…”

Section: Introductionmentioning

confidence: 99%

Free-carrier relaxation and lattice heating in photoexcited bismuth

et al. 2013

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We report ultrafast surface pump and interface probe experiments on photoexcited carrier transport across single crystal bismuth films on sapphire. The film thickness is sufficient to separate carrier dynamics from lattice heating and strain, allowing us to investigate the time-scales of momentum relaxation, heat transfer to the lattice and electron-hole recombination. The measured electron-hole (e − h) recombination time is 12-26 ps and ambipolar diffusivity is 18-40 cm 2 /s for carrier excitation up to ∼ 10 19 cm −3 . By comparing the heating of the front and back sides of the film, we put lower limits on the rate of heat transfer to the lattice, and by observing the decay of the plasma at the back of the film, we estimate the timescale of electron-hole recombination. We interpret each of these timescales within a common framework of electron-phonon scattering and find qualitative agreement between the various relaxation times observed. We find that the carrier density is not determined by the e − h plasma temperature after a few picoseconds. The diffusion and recombination become nonlinear with initial excitation > ∼ 10 20 cm −3 .

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“…Zijlstra et al [13] suggested that coherent E g phonon motion is a result of anharmonic coupling to the DECP-driven A 1g mode, although the E g amplitude estimated by this mechanism is much smaller than that observed. Recent experimental work [7], which measured the decay rate of the force driving the E g mode in bismuth, found that the E g force lifetime varies from 13 fs at low temperature to 2 fs at room temperature and suggested that this low-symmetry force may arise from an initial unbalanced occupation of symmetry-equivalent regions in the Brillouin zone, which rapidly decays via electron-phonon scattering to a fully symmetric occupation.…”

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confidence: 67%