Room Temperature Giant and Linear Magnetoresistance in Topological Insulator ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ Nanosheets

Topological insulators, a new class of condensed matter having bulk insulating states and gapless metallic surface states, have demonstrated fascinating quantum effects. However, the potential practical applications of the topological insulators are still under exploration worldwide. We demonstrate that nanosheets of a ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ topological insulator several quintuple layers thick display giant and linear magnetoresistance. The giant and linear magnetoresistance achieved is as high as over 600% at room temperature, with a trend towards further increase at higher temperatures, as well as being weakly temperature-dependent and linear with the field, without any sign of saturation at measured fields up to 13 T. Furthermore, we observed a magnetic field induced gap below 10 K. The observation of giant and linear magnetoresistance paves the way for 3D topological insulators to be useful for practical applications in magnetoelectronic sensors such as disk reading heads, mechatronics, and other multifunctional electromagnetic applications.

Figure 1

Characterization of ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ nanosheets: (a) Crystal structure of ${\mathrm{Bi}}_2{\mathrm{Te}}_3$. A QL consists of Te-Bi-Te-Bi-Te layers. (b) Schematic diagram of standard four-probe geometry on nanosheets. (c) An AFM image of a platelike ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ nanosheet, with the inset profiles corresponding to the green lines in the AFM image. (d) Low-resolution TEM image of a ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ nanosheet. (e) High-resolution TEM image of the nanosheet edge; the inset is the selected area electron diffraction pattern. The scale bars in (c) and (d) are 200 and 50 nm, respectively.

Figure 2

(a) Temperature dependence of the resistance and magnetoresistance of a ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ nanosheet. (b) Arrhenius plot of $R$ vs $1/T$ for low temperatures. Upper left in (b) shows the sketch of the surface state dispersion near the $\Gamma$ point for 0 and 13 T. Lower right in (b) shows the $R\mathrm{\text{−}}T$ curves between 3 and 55 K.

Figure 3

Field dependence of the transverse magnetoresistance (inset) and the MR ratio between 3 and 340 K for a ${\mathrm{Bi}}_2{\mathrm{Te}}_3$ nanosheet.