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arXiv · 1704.00831

Local optical control of ferromagnetism and chemical potential in a topological insulator

Andrew L. Yeats·Peter J. Mintun·Yu Pan·Anthony Richardella·Bob B. Buckley·Nitin Samarth·David D. Awschalom
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Abstract

Many proposed experiments involving topological insulators (TIs) require spatial control over time-reversal symmetry and chemical potential. We demonstrate reconfigurable micron-scale optical control of both magnetization (which breaks time-reversal symmetry) and chemical potential in ferromagnetic thin films of Cr-(Bi,Sb)$_2$Te$_3$ grown on SrTiO$_3$. By optically modulating the coercivity of the films, we write and erase arbitrary patterns in their remanent magnetization, which we then image with Kerr microscopy. Additionally, by optically manipulating a space charge layer in the underlying SrTiO$_3$ substrates, we control the local chemical potential of the films. This optical gating effect allows us to write and erase p-n junctions in the films, which we study with photocurrent microscopy. Both effects are persistent and may be patterned and imaged independently on a few-micron scale. Dynamic optical control over both magnetization and chemical potential of a TI may be useful in efforts to understand and control the edge states predicted at magnetic domain walls in quantum anomalous Hall insulators.

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Andrew L. Yeats, Peter J. Mintun, Yu Pan, Anthony Richardella, Bob B. Buckley, Nitin Samarth, David D. Awschalom. 2017-04-03. Local optical control of ferromagnetism and chemical potential in a topological insulator. https://doi.org/10.1073/pnas.1713458114

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