The Landau spectrum of bismuth is complex and includes many angle-dependentlines in the extreme quantum limit. The adequacy of single-particle theory todescribe this spectrum in detail has been an open issue. Here, we present astudy of angle-resolved Nernst effect in bismuth, which maps the angle-resolvedLandau spectrum for the entire solid angle up to 28 T. The experimental map isin good agreement with the results of a theoretical model with parabolicdispersion for holes and an extended Dirac Hamiltonian for electrons. Theangular dependence of additional lines in the Landau spectrum allows to uncoverthe mystery of their origin. They correspond to the lines expected for the holeLandau levels in a secondary crystal tilted by 108 degrees, the angle betweentwinned crystals in bismuth. According to our results, the electron reservoirsof the two identical tilted crystals have different chemical potentials andcarriers across the twin boundary have different concentrations. An exceptionalfeature of this junction is that it separates two electron-hole compensatedreservoirs. The link between this edge singularity and the states wrapping athree-dimensional electron gas in the quantum limit emerges as an outstandingopen question.
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