Sensitivity of SQUID-on-tip (SOT) to a magnetic nano-particle

Within the state-of-the-art 3D Ginzburg–Landau (GL) formalism, we investigate the static features of the most sensitive SQUID-on-tip (SOT) device placed on the top of a nano-particle. The SOT sensor’s free energy, Cooper pair density, and screening current density in the loop are investigated for the nano-particle’s various placements and sizes. The dynamic aspects of the device, such as its voltage–current characteristics, are evaluated in the presence of transport current using the two-dimensional (2D) time-dependent GL formalism. The sensitivity of the SOT is examined using quantum oscillations of the device’s depairing current as a function of the nano-particle’s size and location. The location of the nano-particle at the device’s center and closer to the device’s loop is required for optimal SOT sensitivity.