Figure 24.

Nonreciprocity and superconducting diode effect. (a) Schematic diagram showing the superconducting diode effect. Cooper pairing is only stable when current flows from left to right. As a result, the transport response across the sample is dissipationless when current flows from left to right, whereas a resistive behavior is observed when current direction is reversed. (b) Differential resistance as a function of DC current bias of the superconducting phase at $B=0.I_c^{+}$ and $I_c^{-}$ are the critical current with positive and negative DC current bias, respectively. The asymmetry in $I_c^{+}$ and $I_c^{-}$ shows the nonreciprocity. (c) Demonstration of robust zero-field superconducting diode effect. (d, e) Field-training of the superconducting diode: (d) After a positive (negative) field training, the superconducting diode remains as a reverse (forward) diode as shown in the blue (red) curve. (e) Extremely high diode efficiency at large doping, as the zero-resistance regime (shaded part) has shifted totally to the negative current side. (f) Interplay between superconductivity and density-wave state. Longitudinal resistance as a function of temperature and doping, at different magnetic fields. As the magnetic field increases, superconductivity is suppressed and density-wave state (resistance oscillations with 1/4 periodicity) takes over at the low temperature range. Adapted with permission from ref 440. Copyright 2022 Springer Nature.