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arXiv · 0908.2019

Tuning the conductance of Dirac fermions on the surface of a topological insulator

S. Mondal·D. Sen·K. Sengupta·R. Shankar
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Abstract

We study the transport properties of the Dirac fermions with Fermi velocity $v_F$ on the surface of a topological insulator across a ferromagnetic strip providing an exchange field ${\mathcal J}$ over a region of width $d$. We show that the conductance of such a junction changes from oscillatory to a monotonically decreasing function of $d$ beyond a critical ${\mathcal J}$. This leads to the possible realization of a magnetic switch using these junctions. We also study the conductance of these Dirac fermions across a potential barrier of width $d$ and potential $V_0$ in the presence of such a ferromagnetic strip and show that beyond a critical ${\mathcal J}$, the criteria of conductance maxima changes from $\chi= e V_0 d/\hbar v_F = n \pi$ to $\chi= (n+1/2)\pi$ for integer $n$. We point out that these novel phenomena have no analogs in graphene and suggest experiments which can probe them.

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S. Mondal, D. Sen, K. Sengupta, R. Shankar. 2009-08-14. Tuning the conductance of Dirac fermions on the surface of a topological insulator. https://doi.org/10.1103/physrevlett.104.046403

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