IR beamline at the Swiss Light Source

Lerch, Philippe; Quaroni, Luca; Wambach, J.; Schneider, J.R.; Armstrong, Donald B.; Rossetti, Daniel; Mueller, F.; Peier, Peter; Schlott, V.; Carroll, Lee; Friedli, Peter; Sigg, H.; Stutz, S.; Tran, Michaël

doi:10.1088/1742-6596/359/1/012003

Cited by 10 publications

(7 citation statements)

References 9 publications

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“…For the reflectivity measurement, a Bruker Hyperion 3000 microscope was used with a single 15× reflective objective. Infrared radiation was provided by the Swiss synchrotron light source (SLS) and coupled 30 to the Fourier transform spectrometer. The high-brightness provided by the synchrotron source allows a spatial resolution of 30 × 30 µm 2 or better while maintaining high throughput.…”

Section: Experiments and Calculationmentioning

confidence: 99%

Optical properties of Bi2Te2Se at ambient and high pressures

et al. 2012

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The temperature dependence of the complex optical properties of the three-dimensional topological insulator Bi2Te2Se is reported for light polarized in the a-b planes at ambient pressure, as well as the effects of pressure at room temperature. This material displays a semiconducting character with a bulk optical gap of Eg 300 meV at 295 K. In addition to the two expected infrared-active vibrations observed in the planes, there is additional fine structure that is attributed to either the removal of degeneracy or the activation of Raman modes due to disorder. A strong impurity band located at 200 cm −1 is also observed. At and just above the optical gap, several interband absorptions are found to show a strong temperature and pressure dependence. As the temperature is lowered these features increase in strength and harden. The application of pressure leads to a very abrupt closing of the gap above 8 GPa, and strongly modifies the interband absorptions in the mid-infrared spectral range. While ab initio calculations fail to predict the collapse of the gap, they do successfully describe the size of the band gap at ambient pressure, and the magnitude and shape of the optical conductivity.

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Section: Experiments and Calculationmentioning

confidence: 99%

Optical properties of Bi2Te2Se at ambient and high pressures

et al. 2012

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“…Transmission was measured through a flake of BiTeI using an infrared microscope. Optical data at high pressure were acquired up to 15 GPa with a diamond anvil cell (DAC) at the X01DC IR synchrotron beam line of the Swiss Light Source [10,11]. Reflectivity was determined in the frequency range from 60 meV to 1 eV for a dense set of pressures.…”

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confidence: 99%

Infrared- and Raman-Spectroscopy Measurements of a Transition in the Crystal Structure and a Closing of the Energy Gap of BiTeI under Pressure

et al. 2014

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BiTeI is a giant Rashba spin splitting system, in which a noncentrosymmetric topological phase has recently been suggested to appear under high pressure. We investigated the optical properties of this compound, reflectivity and transmission, under pressures up to 15 GPa. The gap feature in the optical conductivity vanishes above p ∼ 9 GPa and does not reappear up to at least 15 GPa. The plasma edge, associated with intrinsically doped charge carriers, is smeared out through a phase transition at 9 GPa. Using high-pressure Raman spectroscopy, we follow the vibrational modes of BiTeI, providing additional clear evidence that the transition at 9 GPa involves a change of crystal structure. This change of crystal structure possibly inhibits the high-pressure topological phase from occurring. DOI: 10.1103/PhysRevLett.112.047402 PACS numbers: 78.20.hb, 62.50.-p, 78.30.Am, 78.40.Fy Interest in the noncentrosymmetric semiconductor BiTeI surged when it was found that this compound hosts the largest known Rashba spin splitting in bulk form [1][2][3]. While this material is structurally related to the recently discovered bismuth chalcogenide topological insulators [4,5], it is an insulator of the common variety at ambient pressure. Recent first-principles band structure calculations suggested that BiTeI undergoes a transition to the topological insulating phase under pressure [6], through which BiTeI would become the first example of noncentrosymmetric topological insulator. Moreover, such a bandstructure topology change realizes a remarkable example of topological phase transition. While several examples of topological phase transitions occurring upon varying chemical composition have been reported in the literature [7][8][9], the pressure-induced transition in BiTeI would present the advantage of being controllable and reversible.Optical conductivity is well suited to probe the band structure of BiTeI under pressure. In this Letter, we determine the high-pressure optical properties by measuring transmission and reflectivity of BiTeI up to 15 GPa. We follow the optical gap under pressure and find that it decreases monotonically until 9 GPa. At this pressure the plasma edge associated with the doped carriers is strongly broadened due to a sudden increase of σ 1 ðωÞ at the plasma frequency. Above this pressure the gap feature in the optical conductivity has disappeared, and it does not reappear to the highest pressure reached. The high-pressure phase appears to be metallic. Using Raman spectroscopy, we observe a sudden change in the number and frequency of the vibrational modes at 9 GPa, which shows that a structural transition occurs at this pressure.Single crystals of BiTeI were grown by the floating zone method, starting from the stoichiometric ratio of metallic bismuth, tellurium and bismuth iodide. The unit cell of BiTeI is composed of triple layers, Te-Bi-I, stacked along the polar c-axis [1]. The triple layers are bound by a weak van der Waals interaction. The structure is described by the noncentrosymmetric space...

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“…High pressure infrared reflectivity spectra were acquired at the infrared beamline of the Swiss Light Source [26] using a diamond anvil cell-based customized setup [27] fitting a Hyperion microscope. Freshly cut ∼ 0.03 × 0.04 × 0.01 mm samples with the surface oriented parallel to the c and b axes were loaded in the sample chamber consisting of CuBe gaskets with ruby chips.…”

Section: Resultsmentioning

confidence: 99%

Pressure-induced structural transitions triggering dimensional crossover in the lithium purple bronze Li0.9Mo6O17

et al. 2021

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At ambient pressure, lithium molybdenum purple bronze (Li 0.9 Mo 6 O 17 ) is a quasi-one-dimensional solid in which the anisotropic crystal structure and the linear dispersion of the underlying bands produced by electronic correlations possibly bring about a rare experimental realization of Tomomaga-Luttinger liquid physics. It is also the sole member of the broader purple molybdenum bronzes family where a Peierls instability has not been identified at low temperatures. The present paper reports a pressure-induced series of phase transitions between 0 and 12 GPa. These transitions are strongly reflected in infrared spectroscopy, Raman spectroscopy, and x-ray diffraction. The most dramatic effect seen in optical conductivity is the metalization of the c axis, concomitant to the decrease in conductivity along the b axis. This indicates that high pressure drives the material away from its quasi-one-dimensional behavior at ambient pressure. Although the first pressure-induced structure of the series is resolved, the identification of the underlying mechanisms driving the dimensional change in the physics remains a challenge.

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IR beamline at the Swiss Light Source

Cited by 10 publications

References 9 publications

Optical properties of Bi2Te2Se at ambient and high pressures

Optical properties of Bi2Te2Se at ambient and high pressures

Infrared- and Raman-Spectroscopy Measurements of a Transition in the Crystal Structure and a Closing of the Energy Gap of BiTeI under Pressure

Pressure-induced structural transitions triggering dimensional crossover in the lithium purple bronze Li0.9Mo6O17

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