Experimental Techniques

Extremely low temperatures are reached using dilution refrigerators which work akin to a conventional, continuously-cooling refrigerator except based on the circulation of isotopes of helium rather than Freon and quantum rather than classical thermodynamics. Our laboratory currently boasts three dilution refrigerators, one cryogen-free ("dry") and two which use liquid helium ("wet"), all of which are fitted with multi-axis superconducting magnets. We additionally have access to a pair of cryogen-free "PPMS" cryostats, one with a 9 T and one with a 14 T magnet. These systems control temperature between 1.7 and 400 K and can reach 50 mK with a dilution refrigerator insert; they can perform a variety of thermodynamic measurements (heat capacity, susceptibility, etc.) along with standard resistance and Hall measurements. We also have a helium-4 cryostat capable of controlling temperature between 1.7 and 400 K designed for optical measurements with diamond anvil cells.

We perform electrical, magnetic, thermal, and optical measurements in these systems.
More reading: Sub-Kelvin ac magnetic susceptometry

Quasi-hydrostatic pressures up to 45 GPa can be reached in the laboratory using diamond anvil cells and tuned in situ via a helium membrane system. Larger samples can be measured to 2.5 GPa using BeCu clamp piston pressure cells. Further precise tuning of symmetry fields can be obtained via homebuilt uniaxial clamp cells.

We perform a wide range of measurements inside the pressure cells, including electrical transport and Hall Effect, magnetic susceptibility, structural and magnetic x-ray diffraction, pump-probe optical spectroscopy, Raman scattering, and synchrotron Mossbauer measurements,

More reading:
Sub-Kelvin magnetic and electrical measurements in a diamond anvil cell with in situ tunability
A compact bellows-driven diamond anvil cell for high-pressure, low-temperature magnetic measurements
Four-probe electrical measurements with a liquid pressure medium in a diamond anvil cell

We are frequent users of the Advanced Photon source at the Argonne National Laboratory, with experiments performed at Sectors 2, 4, 6, 8, 11, 13, 16, and 33. We mainly focus on quantum critical behaviors of both correlated charge and magnetic systems, using diamond anvil cells and mainly x-ray diffraction techniques, including advancing the state of the art in magnetic x-ray diffraction at high pressures.

More reading: X-ray magnetic diffraction under high pressure