New Quantum Ground States Under Pressure: An Investigation of Experimental Extreme Conditions Superconductivity in Barium Tellurium Antimony Sulphate

Barium Tellurium Antimony Sulphate (BSTS) is a newly discovered two-dimensional material that exhibits charge density wave at ambient conditions. Charge density wave (CDW) materials are strongly correlated electron systems that have charge modulations in their structures. CDW and superconductivity (SC) have demonstrated a correlation in many materials and together with previous theories suggest that they could be competitive quantum states. Therefore, charge-density materials are theoretically proposed to be great candidates for pressure-induced superconductivity. High-pressure studies are fundamental in testing these theories and finding new superconductors. Using a diamond anvil cell with a Van der Pauw four probe method utilizing a closed-cycle 2K cryostat, we measured the pressure and temperature dependence of the electrical resistivity of BSTS between 298-3K and 0-20 GPa.

In this work, we find that BSTS exhibits the behavior of a semiconductor below 10GPa. But as pressure increases above the 10GPa threshold, the electrical resistivity of the BSTS closely corresponds instead to the behavior of a bad metal, with electrical resistance having a linear relation to temperature. As BSTS transitions into a bad metal, we also start to observe a rapid drop in resistance at low temperatures which indicates a transition into superconductivity. The corresponding critical temperature of the drop in resistance also continues to increase, allowing resistance to continuously approach zero ohms. Furthermore, corresponding to previous work within the Deemyad lab, this transition from a semiconductor into a metal and superconducting state coincides with suppression of the charge density wave, supporting that there is a competition between the two quantum states within BSTS.