Magnetic field induced reconstruction of electronic structure in Sr3 Ru2 O7 nanosheets

The origin of the large magnetoresistance (MR) peak induced by the metamagnetic transition (MMT) in Sr3Ru2O7 has attracted extensive attention, but still remains puzzling. Here we performed systematic magnetotransport and torque magnetometry measurements of Sr3Ru2O7 nanosheets, and found surprisingly that the MR peak, together with the MMT, shifts dramatically toward low magnetic field with the decrease of thickness. Meanwhile, the Hall coefficient shows clearly a sign change near the MR peak position, indicating a magnetic field induced change of band topology. Combined with the theoretical calculation, we argue that the nature of the MR peak in Sr3Ru2O7 is associated with the so-called Lifshitz transition due to van Hove singularity, which is closer to the Fermi level in thinner nanosheets.