fig2

Figure 2. (A-C) Current-voltage characteristics were measured at 2 K, considering opposite bias polarities (current directions) in a 4-terminal configuration, under zero magnetic field B_z = 0 T, which is always applied parallel to the z direction. The bias sweep direction consistently proceeds from 0 to a finite bias. But for B_z = -0.7 mT. (A) and (B) Measurement for 0 and 300 ions/nm sample; (C) 600 ions/nm sample. There is a difference between two critical currents. With the orientation of the magnetic field reversed, the roles of the two bias polarities are also exchanged; (D-F) The temperature-dependent resistance under different linear fluences ranging from 0 to 600 ions/nm.