Abstract
We report on an optical technique for measuring thermal expansion and magnetostriction at cryogenic temperatures and under applied hydrostatic pressures of 2.0 GPa. Optical fiber Bragg gratings inside a clamp-type pressure chamber are used to measure the strain in a millimeter-sized sample of CeRhIn. We describe the simultaneous measurement of two Bragg gratings in a single optical fiber using an optical sensing instrument capable of resolving changes in length on the order of . Our results demonstrate the possibility of performing high-resolution thermal expansion measurements under hydrostatic pressure, a capability previously hindered by the small working volumes typical of pressure cells.
Highlights
The thermal expansion of a material provides important information to a broad range of fields.Different materials exhibit different changes in length in response to variations in temperature, making the study of thermal expansion crucial to the design of engines, bridges and space shuttles.The anomalous thermal expansion of water, for instance, has a strong impact on biological systems and needs to be accounted for in realistic simulations
The first fiber Bragg grating (FBG) at ∼1535 nm contains only a small amount of adhesive, and the second FBG at ∼1545 nm contains the a-axis needle of CeRhIn5. Both peaks shift to a lower wavelength, as expected from the compression of both the FBG and the sample under hydrostatic pressure
We describe an optical technique for measuring thermal expansion and magnetostriction at cryogenic temperatures (T < 15 K) and under applied pressures of 2.0 GPa
Summary
The thermal expansion of a material provides important information to a broad range of fields.Different materials exhibit different changes in length in response to variations in temperature, making the study of thermal expansion crucial to the design of engines, bridges and space shuttles.The anomalous thermal expansion of water, for instance, has a strong impact on biological systems and needs to be accounted for in realistic simulations. Quantum fluctuations generated at a quantum critical point (QCP) dominate the physical properties of a material over large temperature ranges above T = 0. This leads to anomalous thermodynamic behavior found experimentally in an increasing number of systems, heavy-fermion compounds being a prominent example. The electronic Grüneisen parameter, Γcr , is an important thermodynamic quantity to identify and classify quantum phase transitions because it diverges near a pressure-driven QCP with characteristic exponents for a given theory [4]
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