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 (HC1 and HC2), 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.