Scientists Discover New Asymmetric Topological Insulator

Topological Insulator

A team of scientists has discovered a new asymmetric topological insulator made of many layers of BiTeCl, which enables electrical current to flow differently along its top surface than along its bottom.

Scientists working at SLAC, Stanford, Oxford, Berkeley Lab and in Tokyo have discovered a new type of quantum material whose lopsided behavior may lend itself to creating novel electronics.

In this drawing of the asymmetric topological insulator BiTeCl, the bottom surface contains an excess of electrons while the top surface has an excess of positively charged “holes.” The edge where they meet forms a natural p-n junction, enabling novel device applications. Images below the drawing, taken with the ARPES technique, reveal striking differences in the energy and momentum of electrons in the top (left) and bottom (right) surfaces. Adapted from Y.L. Chen et al, Nature Physics
Asimetrinės topologijos izoliatoriaus BiTeCl piešinys. Apačioje yra elektronų perteklius, o viršutinis paviršius turi teigiamo krūvio perteklių – “skyles”. Kraštas, kur jie susitinka, suformuoja natūralią pn sandūrą. Tai leidžia naujų įrenginių pritaikymus. Paveikslėliai brėžinyje atskleidžia ryškius elektronų energijos ir impulso skirtumus viršutiniame (kairėje) ir apatiniame (dešinėje) paviršiuose. Adaptuota iš Y.L. Chen et al, Nature Physics

The material is called bismuth tellurochloride, or BiTeCl. It belongs to a class of materials called topological insulators that conduct electrical current with perfect efficiency on their surfaces, but not through their middles. Researchers hope to exploit their unusual properties to create “spintronic” devices that use the electron’s spin, rather than just its charge, to carry energy and information with 100 percent efficiency and at room temperature.

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