Invited Article: High-pressure techniques for condensed matter physics at low temperature

Feng, Yejun; Jaramillo, R.; Wang, Jiyang; Ren, Yang; Rosenbaum, T. F.

doi:doi:10.1063/1.3400212

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Absolute optical extinction measurements of single nano-objects by spatial modulation spectroscopy using a white lamp

This article describes a high sensitivity spectrophotometer designed to detect the overall extinction of light by a single nanoparticle (NP) in the 10−4–10−5 relative range, using a transmission measurement configuration. We focus here on the simple and low cost scheme where a white lamp is used as a light source, permitting easy and broadband extinction measurements (300–900 nm). Using a microscope, in a confocal geometry, an increased sensitivity is reached thanks to a modulation of the NP po...

Condensed matter experiments at high pressure accentuate the need for accurate pressure scales over a broad range of temperatures, as well as placing a premium on a homogeneous pressure environment. However, challenges remain in diamond anvil cell technology, including both the quality of various pressure transmitting media and the accuracy of secondary pressure scales at low temperature. We directly calibrate the ruby fluorescence R1 line shift with pressure at T = 4.5 K using high-resolution x-ray powder diffraction measurements of the silver lattice constant and its known equation of state up to P = 16 GPa. Our results reveal a ruby pressure scale at low temperatures that differs by 6% from the best available ruby scale at room T. We also use ruby fluorescence to characterize the pressure inhomogeneity and anisotropy in two representative and commonly used pressure media, helium and methanol:ethanol 4:1, under the same preparation conditions for pressures up to 20 GPa at T = 5 K. Contrary to the accepted wisdom, both media show equal levels of pressure inhomogeneity measured over the same area, with a consistent ΔP/P per unit area of ±1.8 %/(10⁴ μm²) from 0 to 20 GPa. The helium medium shows an essentially constant deviatoric stress of 0.021±0.011 GPa up to 16 GPa, while the methanol:ethanol mixture shows a similar level of anisotropy up to 10 GPa, above which the anisotropy increases. The quality of both pressure media is further examined under the more stringent requirements of single crystal x-ray diffraction at cryogenic temperature. For such experiments we conclude that the ratio of sample-to-pressure chamber volume is a critical parameter in maintaining sample quality at high pressure, and may affect the choice of pressure medium.

Article Outline

INTRODUCTION
CHARACTERIZATION OF PRESSURE MEDIA AT T = 5 K
EXPERIMENTAL CHOICE OF PRESSURE MEDIA
RUBY PRESSURE SCALE CALIBRATION AT T = 4.5 K
CONCLUSIONS

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KEYWORDS and PACS

Keywords

fluorescence, helium, high-pressure effects, organic compounds, ruby, spectral line shift, X-ray diffraction

PACS

62.50.-p

High-pressure effects in solids and liquids
81.40.Vw

Pressure treatment
78.60.-b

Other luminescence and radiative recombination

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http://link.aip.org/link/doi/10.1063/1.3400212

PUBLICATION DATA

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0034-6748 (print)

1089-7623 (online)

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$abstract.society.value is a Member of CrossRef

American Institute of Physics

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