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Dynamics of surface electrons in a topological insulator: cyclotron resonance at room temperature

I. Mohelsky, F. Le Mardele, J. Dzian, J. Wyzula, X. D. Sun, C. W. Cho, B. A. Piot, M. Shankar, R. Sankar, A. Ferguson, D. Santos-Cottin, P. Marsik, C. Bernhard, A. Akrap, M. Potemski, M. Orlita

Abstract

The ability to manipulate the surface states of topological insulators using electric or magnetic fields under ambient conditions is a key step toward their integration into future electronic and optoelectronic devices. Here, we demonstrate - using cyclotron resonance measurements on a tin-doped BiSbTe$_2$S topological insulator - that moderate magnetic fields can quantize massless surface electrons into Landau levels even at room temperature. This finding suggests that surface-state electrons can behave as long-lived quasiparticles at unexpectedly high temperatures.

Dynamics of surface electrons in a topological insulator: cyclotron resonance at room temperature

Abstract

The ability to manipulate the surface states of topological insulators using electric or magnetic fields under ambient conditions is a key step toward their integration into future electronic and optoelectronic devices. Here, we demonstrate - using cyclotron resonance measurements on a tin-doped BiSbTeS topological insulator - that moderate magnetic fields can quantize massless surface electrons into Landau levels even at room temperature. This finding suggests that surface-state electrons can behave as long-lived quasiparticles at unexpectedly high temperatures.

Paper Structure

This paper contains 7 figures.

Figures (7)

  • Figure 1: The real part of optical conductivity of Sn-BST2S deduced by ellipsometry at $T= 5, 50, 100, 200$ and 300 K. The oscillations below the band gap correspond to a delaminated layer with the thickness of $(7 \pm 2)$$\mu$m. The inset shows the low-energy part of the spectrum with two pronounced infrared-active phonons, but no apparent Drude contribution.
  • Figure 2: Low-temperature infrared magneto-reflectivity of BST2S: (a) Stack-plot of magneto-reflectivity spectra, $R_B/R_0$, and (b) false-color plot of the corresponding derivatives, $d/dB [R_B/R_0]$. (c) The energies of observed inter-LL excitations as a function of the magnetic-field component perpendicular to the sample ($B_{\mathrm{perp}}$), extracted as the minima in the $R_B/R_0$ spectra collected in the tilted-field configuration (panel c, upper inset) for the angles $\theta = 0, 50, 60$ and 70 deg. The error bars are given by the size of symbols. Black lines are the fits of the inter-LL transitions, using the model of massless Landau-quantized electrons, yielding the velocity parameter $v=(4.4\pm0.2)\times10^5$ m/s. The observed inter-LL excitations are indicated in the lower inset of panel c.
  • Figure 3: Temperature evolution of the fundamental CR line: (a-e) Relative (double) magneto-transmission of a 7-$\mu$m-thick BST2S layer, $T_B/T_0$, for selected temperatures plotted in a form of false-color plots. (f-j) Magneto-transmission spectra at selected temperatures and magnetic fields applied.
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