Speaker
Description
The two-leg spin ladder $\mathrm{Sr_{14-x}Ca_{x}Cu_{24}O_{41}}$ (SCCO) has been the subject of intense investigation owing to its role as an analogous system to high-temperature cuprate superconductors. Their unique, quasi-1D structure provides a low-dimensional analog to the quintessential $\mathrm{CuO_2}$ planes of cuprates, thus simplifying study of the role of dimensionality and charge-order on superconductivity. The isovalent substitution of Ca increases inter-layer overlap, thus the relative dimensionality, leading to the suppression of a non-Peierls charge density wave (CDW) when the Ca-doping has x > 9. Superconductivity, unexpectedly, emerges at x > 11 exclusively with the application of pressure of at least 3 GPa. To further study this pair of ordered states, we first use THz time-domain spectroscopy to firmly establish the equilibrium response of this complex, highly anisotropic material. Additionally, using a strong-field THz-pump, we observe a THz-driven conductivity modulation in SCCO x = 12. This observation may be the result of charge-transfer facilitated by a transient increase in inter-layer coupling, which could likewise be a key factor in the onset of pressure-dependent superconductivity.