Diode Effect May Assist Finding Proper Superconductivity Mechanism in Copper Oxides

Abstract

We present measurements demonstrating that copper-oxide high-temperature superconductors can exhibit broken time-reversal symmetry in the absence of external magnetic fields. Using $T{l}_{2}B{a}_{2}CaC{u}_2{O}_8$ microbridges, we observe a pronounced superconducting diode effect at 100 K under strictly zero-field conditions. This nonreciprocal response remains unchanged in magnetic fields up to $\pm 100Oe$. Our results are consistent with recent reports of zero-field diode behavior in $B{i}_{2}S{r}_{2}CaC{u}_2{O}_{8+\hat{I}´}$ and together indicate that time-reversal symmetry breaking may be an intrinsic property of the cuprate superconducting state. These findings significantly constrain theoretical models of high-temperature superconductivity that rely on time-reversal-symmetric mechanisms.