Response of a superconductor NbSe₂ flake to magnetic field detected with small tunnel junctions

We have experimentally studied response of a superconductor NbSe₂ flake to perpendicular magnetic fields using small tunnel junctions. The NbSe₂ film (lateral size ~ several μm, thickness ~ 50 nm) was obtained using the mechanical exfoliation of a bulk crystal and was transfered on top of predefined Au electrodes, forming an Au/NbSe₂/Au double SIN tunnel junction system. At 4.2 K, between the lower and upper critical fields (H_C1 and H_C2), the voltage of the Au/NbSe₂/Au structure under constant current of 1 μA exhibited random-telegraph-noise-like fluctuations as a function of the magnetic field which was applied perpendicular to the NbSe₂ flake. The origin of the voltage fluctuations is discussed.