Coherent acoustic phonons in hexagonal manganite LuMnO3

Abstract

We have observed coherent acoustic phonons in the hexagonal manganite LuMnO3 using two-color femtosecond optical pump-probe spectroscopy. The dependence of the oscillatory component of the photoinduced reflectivity on the probe wavelength and incident angle is consistent with a propagating strain pulse. Moreover, the frequency, dephasing, and phase of the oscillation are found to be temperature dependent. In particular, a large phase shift occurs in the vicinity of the Néel temperature (TN), which we relate to the temperature-dependent on-site Mn d–d transition that is coupled to antiferromagnetic ordering, as recently observed in optical conductivity measurements.

Photoexcitation of gigahertz longitudinal and shear acoustic waves in BiFeO3 multiferroic single crystal

“…12,13 More interestingly, it was shown that actually the emitted terahertz radiation reflects the ultrafast modulation of the spontaneous polarization of BFO which offers approaches to readout in nonvolatile random access memories and ferroelectric domain imaging systems. In addition, such pump-probe technique allows access to the photo-induced coherent acoustic phonons dynamics 18 which provides access to the determination of the elastic properties and also provides insight on the coupling of phonons and light. In this letter, we show that coherent acoustic waves are efficiently photogenerated and photodetected in BFO by using femtosecond laser pulses.…”

“…More specificaly, ultra-fast optical pump-probe spectroscopy can bring insights into the fundamental microscopic dynamics, important in many applications, that are at the origin of functional properties of various materials such as metals, 14 semiconductors, 15 collossal magnetoresistive manganites, 16 superconductors, 17 or multiferroics. 12,13,18 Such technique was used to investigate the model multiferroic BFO. As a result using femtosecond laser pulses, it was shown that coherent terahertz electromagnetic waves emission is possible.…”

Propagating coherent acoustic phonon wave packets inInxMn1−xAs∕GaSb

“…While femtosecond spectroscopy has previously been used for generating and detecting coherent phonons in many materials (e.g, optical phonons in bulk semiconductors, metals (Bi, Sb) and superconductors; acoustic phonons in InGaN/GaN-based semiconductor heterostructures [7,8,9,10,11,12,13]), only recently has there been interest in the application of this technique to probing coherent excitations (e.g., phonons and magnons) in strongly-correlated electronic systems [14,15]. These innovative studies further demonstrate the potential of transient reflectivity spectroscopy to unravel the subtle interplay between lattice and spin excitations.…”

“…While originally the oscillations were believed to originate from the ferromagnetism (since they were not observed in similiar systems without Mn doping), a systematic study shows that they instead result from * Permanent address: Graduate School of Science and Technology, Chiba University, Chiba, Japan † Author to whom correspondence should be addressed; Electronic address: kono@rice.edu ‡ Present address: Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, JAPAN the generation of coherent phonons in the InMnAs layer which then propagate into the GaSb. The period and the characteristic decay time of the transient reflectivity oscillations are consistent with a propagating coherent acoustic phonon wavepacket model [7].While femtosecond spectroscopy has previously been used for generating and detecting coherent phonons in many materials (e.g, optical phonons in bulk semiconductors, metals (Bi, Sb) and superconductors; acoustic phonons in InGaN/GaN-based semiconductor heterostructures [7,8,9,10,11,12,13]), only recently has there been interest in the application of this technique to probing coherent excitations (e.g., phonons and magnons) in strongly-correlated electronic systems [14,15]. These innovative studies further demonstrate the potential of transient reflectivity spectroscopy to unravel the subtle interplay between lattice and spin excitations.…”

The influence of charge and magnetic order on polaron and acoustic phonon dynamics in LuFe2O4

“…The observed oscillations are typically attributed to coherent acoustic phonons, which can be manifested as propagating strain waves, generated through the dynamic stress induced by absorption of the femtosecond laser pulses within the penetration depth. 26 These strain waves have often been observed in ultrafast optical experiments on correlated electron materials [27][28][29] and semiconductors, 30,31 with an oscillation period that depends on the probe wavelength, given by…”