Extended Data Fig. 1: Weak nonreciprocity in normal state transport in sample B.
From: Zero-field superconducting diode effect in small-twist-angle trilayer graphene
a, Rxx versus T measured at B = 0 and νtTLG = 2.5 in sample B. Tc is around 0.95 K, defined by the onset in Rxx with increasing temperature. b, dV/dI measured with Idc = + 200nA (red dots) and − 200 nA (blue dots) as a function of temperature in the temperature range T > Tc. c, Renormalized dV/dI showing the difference between Idc = ± 200 nA as a function of T. The difference in dV/dI between Idc = ± 200 nA is around 50Ω, which is consistent with the very weak nonreciprocity at Idc > Ic at low temperature (Extended Data Fig. 5b). This nonreciprocity decreases with increasing temperature and completely vanishes at T > 6 K. This observation is consistent with an underlying fermi surface with partial valley imbalance, which simultaneously breaks time-reversal and inversion symmetries. The valley imbalance, hence time-reversal symmetry breaking, onsets spontaneously at T ≈ 6 K. Even though time-reversal and inversion symmetries are broken in the normal state, nonreciprocity is greatly enhanced by the onset of the superconducting phase.
