Temperature Induced Shifts of Yu-Shiba-Rusinov Resonances in Nanowire-Based Hybrid Quantum Dots

The strong coupling of a superconductor to a spinful quantum dot results in Yu–Shiba–Rusinov discrete subgap excitations. In isolation and at zero temperature, the excitations are sharp resonances. In transport experiments, however, they show as broad differential conductance peaks. Here we obtain the lineshape of the peaks and their temperature dependence in superconductor–quantum dot–metal nanowire-based devices. Unexpectedly, we find that the peaks shift in energy with temperature, with the shift magnitude and sign depending on ground state parity and bias voltage. Additionally, we empirically find a power-law trend of the peak area versus temperature. These observations are not explained by current models. Yu–Shiba–Rusinov subgap excitations are associated with a range of interesting physics such as Majorana fermions, and so it is important to understand their intrinsic features. Here, the authors investigate the temperature dependence of the Yu–Shiba–Rusinov states in a hybrid nanowire–quantum dot system, demonstrating that the shift in energy does not follow the behaviour predicted by current models.