Coherent generation of symmetry-forbidden phonons by light-induced electron-phonon interactions in magnetite

Borroni, Simone; Baldini, Edoardo; Katukuri, Vamshi M.; Mann, Andreas; Parliński, K.; Legut, Dominik; Arrell, Christopher; Mourik, Frank van; Teyssier, J.; Kozłowski, A.; Piekarz, Przemysław; Yazyev, Oleg V.; Oleś, Andrzej M.; Lorenzana, J.; Carbone, Fabrizio

doi:10.48550/arxiv.1507.07193

Cited by 3 publications

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“…Optical measurements provide an efficient tool to unravel the changes of electronic and structural properties at the phase transition. [18][19][20][21] In magnetite, the equilibrium optical conductivity [22][23][24] shows a broad Drude peak in the metallic phase as well as its suppression at the metal-insulator transition. The optical properties at higher energies are dominated by two features peaking at about 0.6 eV and 2 eV.…”

Section: Introductionmentioning

confidence: 99%

Phase separation in the nonequilibrium Verwey transition in magnetite

et al. 2016

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We present equilibrium and out-of-equilibrium studies of the Verwey transition in magnetite. In the equilibrium optical conductivity, we find a step-like change at the phase transition for photon energies below about 2 eV. The possibility of triggering a non-equilibrium transient metallic state in insulating magnetite by photo excitation was recently demonstrated by an x-ray study. Here we report a full characterization of the optical properties in the visible frequency range across the nonequilibrium phase transition. Our analysis of the spectral features is based on a detailed description of the equilibrium properties. The out-of-equilibrium optical data bear the initial electronic response associated to localized photo-excitation, the occurrence of phase separation, and the transition to a transient metallic phase for excitation density larger than a critical value. This allows us to identify the electronic nature of the transient state, to unveil the phase transition dynamics, and to study the consequences of phase separation on the reflectivity, suggesting a spectroscopic feature that may be generally linked to out-of-equilibrium phase separation.

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Section: Introductionmentioning

confidence: 99%

Phase separation in the nonequilibrium Verwey transition in magnetite

et al. 2016

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“…The exploration of the speed limits of phase transitions between macroscopically ordered phases of condensed matter systems has evolved into a central branch of physics, including the study of magnetic phase transitions [1][2][3], metal-insulator transitions [4][5][6][7] and lightinduced superconductivity [8,9]. Moreover, recently, this investigation has even been extended to multiferroic systems, which already in the ground state can exhibit both electric and magnetic order and the coupling between them can give rise to highly non-trivial dynamics, such as large amplitude spin-cycloid rotation [10], colossal dynamical magnetoelectric effect [11], and optically driven ultrafast transition from collinear antiferromagnetic (AFM) to spiral states in the multiferroic CuO [12].…”

Section: Introductionmentioning

confidence: 99%

Ultrafast cooling and heating scenarios for the laser-induced phase transition in CuO

2016

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The multiferroic compound CuO exhibits low-temperature magnetic properties similar to antiferromagnetic iron oxides, while the electronic properties have much more in common with the high-T c cuprate superconductors. This suggests novel possibilities for the ultrafast optical excitation of magnetism. On the basis of atomistic spin dynamics simulations, we study the effect of phonon-assisted multimagnon absorption and photodoping on the spin dynamics in the vicinity of the first-order phase transition from collinear to spin-spiral magnetic order. Similar as in recent experiments, we find that for both excitations the phase transition can proceed on the picosecond timescale. Interestingly, however, these excitation mechanisms display very distinct dynamics. Following photodoping, the spin system first cools down on subpicosecond time scales, which we explain as an ultrafast magnetocaloric effect. Opposed to this, following phonon-assisted multimagnon excitation, the spin systems rapidly heats up and subsequently evolves to the noncollinear phase even under the influence of isotropic exchange interactions alone.

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“…The combination of the ISRS framework and the use of a broad window of detection in the optical range allows one to address a pivotal aspect of the paradigm behind strongly correlated quantum systems, i.e. the coupling between Raman-active low-energy (tens of meV) bosonic modes and high-energy (∼ eV) charge excitations on the Mott scale [11][12][13][14][15][16][17] .…”

Section: Introductionmentioning

confidence: 99%

A versatile setup for ultrafast broadband optical spectroscopy of coherent collective modes in strongly correlated quantum systems

Baldini

Mann

Borroni

et al. 2016

Structural Dynamics

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A femtosecond pump-probe setup is described that is optimised for broadband transient reflectivity experiments on solid samples over a wide temperature range. By combining high temporal resolution and a broad detection window, this apparatus can investigate the interplay between coherent collective modes and high-energy electronic excitations, which is a distinctive characteristic of correlated electron systems. Using a single-shot readout array detector at frame rates of 10 kHz allows resolving coherent oscillations with amplitudes <10−4. We demonstrate its operation on the charge-transfer insulator La2CuO4, revealing coherent phonons with frequencies up to 13 THz and providing access into their Raman matrix elements.

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Coherent generation of symmetry-forbidden phonons by light-induced electron-phonon interactions in magnetite

Cited by 3 publications

References 0 publications

Phase separation in the nonequilibrium Verwey transition in magnetite

Phase separation in the nonequilibrium Verwey transition in magnetite

Ultrafast cooling and heating scenarios for the laser-induced phase transition in CuO

A versatile setup for ultrafast broadband optical spectroscopy of coherent collective modes in strongly correlated quantum systems

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