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Résumé |
Topological materials, such as topological insulators or semimetals, usually not
only reveal the nontrivial properties of their electronic wavefunctions through
the appearance of stable boundary modes, but also through very specific
electromagnetic responses. The anisotropic longitudinal magnetoresistance of
Weyl semimetals, for instance, carries the signature of the chiral anomaly of
Weyl fermions. However, for topological nodal line (TNL) semimetals – materials
where the valence and conduction bands cross each other on one-dimensional
curves in the three-dimensional Brillouin zone – such a characteristic has been
lacking. Here we report the discovery of a peculiar charge transport effect
generated by TNLs: a dissipationless transverse signal in the presence of
coplanar electric and magnetic fields, which originates from a Zeeman induced
conversion of TNLs into Weyl nodes under infinitesimally small magnetic fields.
We evidence this dissipationless topological response in trigonal PtBi2
persisting up to room temperature, and unveil the extensive TNLs in the band
structure of this non-magnetic material [1,2]. These findings provide a new
pathway to engineer Weyl nodes by arbitrary small magnetic fields and reveal
that bulk topological nodal lines can exhibit non-dissipative transport
properties. |
