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Abstract:
Electron-like carriers in bismuth are described by the Dirac
Hamiltonian, with a band mass becoming a thousandth of the bare electron
mass along one crystalline axis(1). The existence of three anisotropic
valleys offers electrons an additional degree of freedom, a subject of
recent attention(2). Here, we map the Landau spectrum by angle-resolved
magnetostriction, and quantify the carrier number in each valley: while
the electron valleys keep identical spectra, they substantially differ
in their density of states at the Fermi level. Thus, the electron fluid
does not keep the rotational symmetry of the lattice at low temperature
and high magnetic field, even in the absence of internal strain. This
effect, reminiscent of the Coulomb pseudogap in localized electronic
states, affects only electrons in the immediate vicinity of the Fermi
level. It presents the most striking departure from the non-interacting
picture of electrons in bulk bismuth.
