Spin-selective tunneling from nanowires of the candidate topological Kondo insulator SmB ₆

Abstract

Incorporating relativistic physics into quantum tunneling can lead to exotic behavior such as perfect transmission through Klein tunneling. Here, we probed the tunneling properties of spin-momentum-locked relativistic fermions by designing and implementing a tunneling geometry that uses nanowires of the topological Kondo insulator candidate samarium hexaboride. The nanowires are attached to the end of scanning tunneling microscope tips and used to image the bicollinear stripe spin order in the antiferromagnet Fe 1.03 Te with a Neel temperature of about 50 kelvin. The antiferromagnetic stripes become invisible above 10 kelvin concomitant with the suppression of the topological surface states in the tip. We further demonstrate that the direction of spin polarization is tied to the tunneling direction. Our technique establishes samarium hexaboride nanowires as ideal conduits for spin-polarized currents.

Visualizing the atomic-scale origin of metallic behavior in Kondo insulators

“…These Kondo holes nucleate nanometer-scale metallic puddles that could explain many of the strange phenomena detected by bulk probes. More broadly, the sensitivity to local charge within a Kondo lattice may enable atomic-scale charge imaging using STM tips decorated with a Kondo impurity ( 61 ) or fabricated from heavy-fermion materials ( 62 ).…”

“…These Kondo holes nucleate nanometer-scale metallic puddles that could explain many of the strange phenomena detected by bulk probes. More broadly, the sensitivity to local charge within a Kondo lattice may enable atomic-scale charge imaging using STM tips decorated with a Kondo impurity (61) or fabricated from heavy-fermion materials (62). (C) The intensity of backscattering from topological states, calculated from Fourier-filtering dI/dV at the y component of the backscattering wave vector q y ¼ 2k ss y , is strongly peaked around each Kondo hole.…”

How to identify and characterize strongly correlated topological semimetals

“…In this first work, a topologically nontrivial insulating state was found to result from the spin-orbit coupling associated with the hybridization between the conduction and localized (f ) electrons, in particular for certain positions of the renormalized f level relative to the bottom of the conduction band and for certain crystal symmetries at the f electron site. This proposal raised great interest and triggered massive efforts [24][25][26][27][28][29][30][31][32][33][34][35][36][37]. Nevertheless, in spite of considerable progress, there is no broad consensus yet on the topological nature of the observed surface states.…”