Twin sample chamber for simultaneous comparative transport measurements in a diamond anvil cell.

In static high pressure experiments, performed within a diamond anvil cell (DAC), several different methods of thermometry may be employed to determine the temperature of the sample. Due to different DAC designs or particular experimental designs or goals, uncertainties in the determination of the temperature of a given sample exist. To overcome the inaccuracy in comparing the temperature dependence of transport properties of different materials at high pressure, we have used a novel design of resistivity measurement in a twin sample chamber built on an insulated gasket in a DAC. In this design, the transport properties of two samples will be measured simultaneously and therefore the two samples will always be in the same relative temperatures. The uncertainties in the temperatures of the two samples will be exactly the same and therefore their relative phase diagram will be compared precisely. The pressures of the chambers can be slightly different and is easily determined by the ruby pieces placed in each chamber. To demonstrate the feasibility of this method we have compared the superconducting properties of two YBa2Cu3O(7-x) (0 ≤ x ≤ 0.65) samples with slightly different superconducting transition temperatures at ambient pressure as a function of pressures up to 11 GPa. The upper limit of the pressure achieved using this design would be lower than single chamber gaskets. The highest achievable pressure, as in a conventional single hole setup, depends upon the thickness of the gasket, the culet size, the size, and symmetry of the sample chamber. For the twin chamber, it also depends upon the separation of the holes from each other as well as from the edge of the culet.