Pressure generation of toroidal anvil cell for physical property investigation under ultra-high pressure 2019/5/29 Shimizu Lab Kara Yusuke

Introduction ・High Pressure ・Applied pressure ⇒ Change atomic distance 1 GPa : about 10,000 atm center of the Earth : about 360 GPa ・Applied pressure ⇒ Change atomic distance results: change electron state structure type metalization superconductivity...etc. ・Predicted the pressure of hydrogen’s metallization and become superconductivity is about 500 GPa . N. W. Ashcroft, Phs. Rev. Lett. 21, 1748 (1968)

Diamond anvil cell (DAC) Sample can generate high pressure (~300 GPa) can measure electrical resistance X-ray diffraction

Culet: a flat surface on the tip of a diamond anvil Introduction How to increase pressure Make smaller culet size. 100 kg / 1 mm² = 10×1010 Pa = 10 GPa 100 kg / 0.1 mm2 = 10×1011 Pa = 100 GPa 100 kg / 0.01 mm2 = 10×1012 Pa = 1000 GPa Culet: a flat surface on the tip of a diamond anvil Lateral support prevent from being broken diamond anvil.

Paper introduction Toroidal diamond anvil cell for detailed measurements under extreme static pressure Agnes Dewaele, Paul Loubeyre, Florent Occelli, Olivier Marie and Mohamed Mezouar A. Dewaele et al.: Nature Commun., 9, 2913 (2018)

Purpose Searched for a design of the diamond anvil that would enable to optimize the anvil strain so as to reach pressures up to the TPa range. Calibrate equation of state above 400 GPa.

Anvil design and sample Run d 1 (μm) d 2 (μm) Sample 1 16 60 Au 2 Au+KCl 3 Al+Au 4 Al 5 25 75 Ar 30 𝛍𝐦 30 𝛍𝐦

Pressure measurement In five runs, always succeeded in generating pressures over 300 GPa, especially run1 reached up to 603 GPa. Run d 1 (μm) d 2 (μm) Sample P max (GPa) 1 16 60 Au 603 2 Au+KCl 443 3 Al+Au 317 4 Al 368 5 25 75 Ar 429

Anvil deformation The anvil was designed with a dome shape, trying to compensate the deformation of the diamond tip, called cupping, under very high pressure.

Pressure dependence of volume of gold Run1,2,3 Volume of gold measured up to 603 GPa is based on the (111) diffraction line position.

Methods X-ray diffraction measurement X ray wavelength 0.3738 Å Pressure determination All runs pressure at the center of the toroidal-DAC measured using the XRD signal of rhenium gasket. Re EoS :Anzellini form S. Anzellini et al .: J. Appl. Phys., 115, 043511 (2014) X ray DAC

Equation of state of Al and Ar Volume of Al and Ar compared with the EoS obtained by a fit of lower pressure data points.

Summary All runs succeeded in generating pressures over 300 GPa, especially run1 reached up to 603 GPa. The data quality will enable researchers to solve some of the current pressure calibration issue above 400 GPa.

The toroidal anvil are made by FIB. My work (Anvil design and processing) 20 μm 50 μm 70 μm 30 μm 3 μm before processing after processing The toroidal anvil are made by FIB. FIB: 集束イオンビーム

My work (Experimental method) Sample : Ca Gasket : Re Insulating layer : c-BN, CaSO4 Electrode : Pt

My work (resistance measurement) Success measurement electrical resistance by using toroidal diamond anvil.