Fig. 4: Non-local magnetotransport of FIB-cut grooves.
From: Transport evidence for chiral surface states from three-dimensional Landau bands
a, Landau band structure of bismuth when a magnetic field B ≈ 15 T is applied along the bisectrix axis (Ny = 1,500). The magnetic field is strong enough for all electron pockets at the L point from different valleys (e1–e3) to be in the quantum limit, except the hole pocket (h) at the T point. The dashed orange line indicates the kz momentum for the surface spectral density in b. The insets depict the sketch of the Brillouin zone and Fermi surfaces of bismuth. b, Surface spectral density for B ≈ 15 T for a slab thickness of Ny = 1,500 unit cells. The localized states on opposite sidewalls are differentiated by yellow and blue. The chiral surface states (CS) manifest an imbalance between right- and left-moving modes on each surface, whereas the trivial surface states (TS) come in pairs of right and left movers per surface. c, Conductance of individual groove Ggroove as a function of groove depth, with B = 14 T along the bisectrix at T = 2 K. The error bars represent the variation obtained by averaging two longitudinal voltage pairs of the Hall-bar structure. d, Scanning electron microscopy image of a non-local geometry device, after cutting three grooves (red lines) between each longitudinal electrodes pair (top). Bottom: schematics of the local (left) and non-local configurations (right) of current and voltage electrodes. The effective current paths via chiral boundary states in the device are highlighted as arrows. e,f, Magnetic-field-dependent local resistance RL (e) and non-local RNL (f) at T = 2 K, where RL(NL) = VL(NL)/I, before (black) and after (red) cutting three grooves.
