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Vidya Madhavan, University of Illinois at Urbana Champaign

Condensed Matter Seminar - "Spin-selective tunneling generated from nanowires of the topological Kondo insulator SmB6"

Event Type
Physics - Condensed Matter
ESB 190
Oct 21, 2022   1:00 pm  
Vidya Madhavan, University of Illinois at Urbana Champaign
Stephen Bullwinkel
Originating Calendar
Physics - Condensed Matter Seminar

Amongst the different classes of topological materials, interaction driven topological phases where the band gaps may be naturally pinned to the Fermi level are ideal systems to generate and manipulate spin-polarized surface state currents. In this talk I will describe our experiments where we use nanowires of the topological Kondo insulator, SmB6 to generate and measure spin-polarized currents of Dirac surface states. Using nanofabrication techniques, we attach SmB6 nanowires to the end of scanning tunneling microscope (STM) tips, effectively making a functional probe with atomic resolution. The tips are used to image the canonical spin density wave material, Fe1+xTe which hosts a bicollinear spin order with a Neel temperature of ~50 K. STM images show a superstructure with the periodicity of the antiferromagnetic order, indicating spin-selective tunneling from the nanowire. The antiferromagnetic order becomes invisible above 10 K, far below the Neel temperature, together with the diminishing topological surface states. We further confirm a smoking gun signature of topological spin-polarized currents by imaging the contrast reversal of the antiferromagnetic order at opposite bias voltages. Our findings demonstrate that the topological surface states in SmB6 nanowires are conduits for robust spin-polarized currents.

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