Zero-bias conductance peaks induced by Yu-Shiba-Rusinov spin screening in double quantum dots*

The subgap states of hybrid superconducting semiconductor nanowire devices possess rich physical phenomena, including Andreev bound states and Majorana bound states. Most transport experiments distinguish them by measuring the zero-bias conductance peaks (ZBCPs), which is still ambiguous. In this work, we demonstrate that robust ZBCPs can be induced by Yu-Shiba-Rusinov (YSR) spin screening in such hybrid device with a double-quantum-dot structure, one coupled to a normal metal and another to a superconductor. Through tunneling spectroscopy, we identified several regimes of different coupling strength in gate space, as well as the singlet and doublet states with or without YSR spin screening. Interestingly, when an axial magnetic field was applied, we observed robust ZBCPs for the spin screened states, but not for the unscreened states. This provides an important mechanism for the formation of ZBCPs and a relevant comparison to benchmark Majorana bound states.