Negative longitudinal magnetoresistance from anomalous N=0 Landau level in topological materials

Understand

Negative longitudinal magnetoresistance (NLMR) is shown to occur in topological materials in the extreme quantum limit, when a magnetic field is applied parallel to the excitation current.

• We perform pulsed and DC field measurements on Pb1-xSnxSe epilayers where the topological state can be chemically tuned.
• The NLMR is observed in the topological state, but is suppressed and becomes positive when the system becomes trivial.
• In a topological material, the lowest N=0 conduction Landau level disperses down in energy as a function of increasing magnetic field, while the N=0 valence Landau level disperses upwards.