Characteristics and development of the coherent synchrotron radiation sources for THz spectroscopy

Barros, Joanna; Évain, C.; Roussel, Eléonore; Manceron, L.; Brubach, J.-B.; Tordeux, Marie-Agnès; Couprie, M.E.; Bielawski, S.; Szwaj, C.; Labat, M.; Roy, Pascale Le

doi:10.1016/j.jms.2015.03.012

Cited by 10 publications

(12 citation statements)

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“…This double vibronic process provides a natural path for spin-lattice quadrupolar coupling that amplifies The measurements were performed using a Tb 2 Ti 2 O 7 single crystal grown by the floating zone technique previously described in [18,20]. We have measured the polarization dependent THz spectrum in the 0.2-1.0 THz (0.82-4.14 meV) energy range using both standard (SSR) [31] and coherent synchrotron radiation (CSR) [32,33] techniques. Focus is given to the "high temperature" regime, from 300 K to 6 K. Four plaquettes, 2 mm in diameter, were chosen to test the magnetoelectric activity of the excited modes according to the main cubic symmetry axes.…”

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“…We have measured the polarization dependent THz spectrum in the 0.2-1.0 THz (0.82-4.14 meV) energy range using both standard (SSR) [31] and coherent synchrotron radiation (CSR) [32,33] techniques. Focus is given to the "high temperature" regime, from 300 K to 6 K. Four plaquettes, 2 mm in diameter, were chosen to test the magnetoelectric activity of the excited modes according to the main cubic symmetry axes.…”

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confidence: 99%

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Double vibronic process in the quantum spin ice candidate Tb2Ti2O7 revealed by terahertz spectroscopy

et al. 2017

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The origin of quantum fluctuations responsible for the spin liquid state in Tb2Ti2O7 has remained a long standing problem. By synchrotron-based terahertz measurements, we show evidence of strong coupling between the magnetic and lattice degrees of freedom that provides a path to the quantum melting process. As revealed by hybrid crystal electric field-phonon excitations that appear at 0.67 THz below 200 K, and around 0.42 THz below 50 K, the double vibronic process is unique for Tb 3+ in the titanate family due to adequate energy matching and strong quadrupolar moments. The results suggest that lattice motion can indeed be the driving force behind spin flips within the hybridized ground and first excited states, promoting quantum terms in the effective Hamiltonian that describes Tb2Ti2O7.Keywords: THz spectroscopy, pyrochlore, frustration, spin-lattice coupling Over the last decade, spin-ice physics has aroused significant attention [1, 2]. It emerges in pyrochlore magnets, such as Ho 2 Ti 2 O 7 or Dy 2 Ti 2 O 7 , as a result of effective ferromagnetic interactions coupling the Ising-like rare-earth magnetic moments constrained along the local 111 directions by the crystal field [3][4][5] (Fig. 1 (a,b)). This combination impedes long-range order, favoring a disordered and macroscopically degenerate magnetic state governed by an organizing principle, the socalled "ice rule," where two spins point into and two out of each elementary tetrahedron in the structure [3].The possibility that quantum fluctuations can melt the spin ice state is a topical issue. It is expected to lead to a wealth of exotic phenomena such as a quantum superposition of "two-in two-out" configurations and emergent electrodynamics with new deconfined particles [6][7][8][9][10][11].In this context, the puzzling behavior of the spin liquid Tb 2 Ti 2 O 7 has attracted much attention. Despite effective antiferromagnetic interactions, Tb 2 Ti 2 O 7 features no long-range order [12,13], however short-range correlations are present over a broad temperature range [14][15][16]. Remarkably, the ground state supports elastic power law spin correlations [17,18], bearing some resemblance to the pinch point pattern observed in spin ices [19]. Below 300 mK, a dispersing low-energy collective mode is found to emerge from these pinch points, reaching its maximum energy at ∼0.25 meV [20]. This signal likely corresponds to fluctuations between the two |± electronic states of the crystal electric field (CEF) ground state doublet. It was interpreted as a signature of interactions between quadrupoles, highlighting the importance of those degrees of freedom [18,[20][21][22]. This is because the non-Kramers nature of Tb 3+ ions prevents magnetic exchange alone from inducing such fluctuations within the Ising-like ground state [22][23][24].A property that distinguishes Tb 2 Ti 2 O 7 from the other rare-earth titanates is the CEF energy spectrum of Tb 3+ . It features a first excited doublet at a low energy of ∆ ≈ 1.5 meV above the ground state [25][26][27][28][29], ...

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Double vibronic process in the quantum spin ice candidate Tb2Ti2O7 revealed by terahertz spectroscopy

et al. 2017

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“…To test the magnetic activity of observed excitations, experiments were performed at 5 K from 0 to 5 T. However, we observed no magnetic field effects and therefore only 0 T measurements are presented here. Transmission spectra of the x = 0, 3, 7, and 11 samples in the 0.2-1.2 THz (6.7-40 cm −1 ) spectral range were performed at the SOLEIL synchrotron AILES beamline operating with coherent synchrotron radiation (CSR) in a low-α configuration providing a high-power polarized radiation source in the sub-THz energy range [41,42]. The samples were mounted to an Attocube rotation stage thermally coupled to the cold head of a Cryomech PT 405 pulse tube cryostat, achieving sample temperatures from 16-300 K. Spectra were collected using a Bruker IFS125 FTIR Michelson interferometer with a 125-μm mylar beam splitter and 1.6-K Si Bolometer detector at 0.5-cm −1 resolution.…”

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Effects of Ca substitution on quasiacoustic sliding modes in Sr14−xCaxCu24O41

et al. 2019

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The low-energy lattice dynamics of the quasiperiodic spin-ladder cuprate Sr14-xCaxCu24O41 are investigated using terahertz frequency synchrotron radiation. A high density of low-lying optical excitations is present in the 1-3 THz energy range, while at least two highly absorbing excitations stemming from long-wavelength acoustic oscillations of the incommensurate chain and ladder sublattices, are observed at subterahertz frequencies. The effects of Ca substitution on the subterahertz quasiacoustic sliding mode gaps is investigated using coherent synchrotron radiation. Analysis of the results suggest increasing substitution of Sr for Ca is accompanied by a transfer of spectral weight between sliding modes associated with different chain-ladder dynamics. The observation is consistent with a transfer of hole charges from the chains to the ladders and modification of the sublattice dimensions following Ca substitution. The results are discussed in context to the significance of low-lying vibrational dynamics and electron-phonon coupling in the superconducting state of certain quasiperiodic systems.

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“…This density is so high that the light emitted by the electrons affects the dynamics of neighboring electrons in a dramatic way. In particular, this nonlinear collective effect leads to spontaneous formation of small-scale structures (in the sub- * Corresponding author : serge.bielawski@univ-lille.fr millimeter to centimeter range) in the longitudinal profile of electron bunches [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. This is known as the microbunching instability [3,4,18,19] (see Figure 1) .…”

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From self-organization in relativistic electron bunches to coherent synchrotron light: observation using a photonic time-stretch digitizer

Bielawski¹,

Blomley²,

Brosi³

et al. 2019

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In recent and future synchrotron radiation facilities, relativistic electron bunches with increasingly high charge density are needed for producing brilliant light at various wavelengths, from X-rays to terahertz. In such conditions, interaction of electron bunches with their own emitted electromagnetic fields leads to instabilities and spontaneous formation of complex spatial structures. Understanding these instabilities is therefore key in most electron accelerators. However, investigations suffer from the lack of non-destructive recording tools for electron bunch shapes. In storage rings, most studies thus focus on the resulting emitted radiation. Here, we present measurements of the electric field in the immediate vicinity of the electron bunch in a storage ring, over many turns. For recording the ultrafast electric field, we designed a photonic time-stretch analog-to-digital converter with terasamples/second acquisition rate. We could thus observe the predicted link between spontaneous pattern formation and giant bursts of coherent synchrotron radiation in a storage ring.

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Characteristics and development of the coherent synchrotron radiation sources for THz spectroscopy

Cited by 10 publications

References 19 publications

Double vibronic process in the quantum spin ice candidate Tb2Ti2O7 revealed by terahertz spectroscopy

Double vibronic process in the quantum spin ice candidate Tb2Ti2O7 revealed by terahertz spectroscopy

Effects of Ca substitution on quasiacoustic sliding modes in Sr14−xCaxCu24O41

From self-organization in relativistic electron bunches to coherent synchrotron light: observation using a photonic time-stretch digitizer

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