Pressure-Induced Transition in Magnetoresistance of Single-Walled Carbon Nanotubes

We applied hydrostatic pressure (up to 10 GPa) to single-walled carbon nanotube bundles at low temperature (down to 2 K) to measure their magnetoresistance (MR) in a field up to 12 T. We found a pressure-induced transition in MR from positive to negative in the high-field regime. The onset of the transition occurs at $\sim 1.5\mathrm{GPa}$, which correlates closely with the tube shape transitions. The characteristics of the high-pressure MR are consistent with a model of pressure-induced two-dimensional weak localization.

Figure 1

The SWNT bundles’ resistance vs temperature at zero pressure and in zero magnetic field. Inset 1: schematic illustration of the four-probe measurement in the DAC, together with a scanning electron microscope image of the sample. The magnetic field is perpendicular to the tubes axes. Inset 2: measured differential conductance vs bias voltage.

Figure 2

(a) The field dependence of MR at different pressures. The curves from 1.5 to 3.5 GPa show the transition region. (b) Contour plot of MR as the functions of pressure and magnetic field.

Figure 3

$\Delta G$ at different temperatures as a function of scaled field ($B/B_{\varphi }$) collapse onto a universal curve (the solid line), as described by Eq. (1) predicted by the 2DWL theory. Upper left inset: detailed comparison in low fields between the data measured at 7 K and theory. Lower right inset: the fitting parameter $B_{\varphi }$ vs temperature, showing a linear dependence corresponding to $p=1$.

Figure 4

(a) Scaled $\Delta G/\Gamma$ at different pressures as a function of scaled field $B/B_{\varphi }$, collapsing onto a universal curve as described by Eq. (1) (the solid line), illustrating a similar scaling law as to temperature. Lower inset: The fitting parameter $B_{\varphi }$ vs $1/P$, showing an inverse linear dependence of $B_{\varphi }$ on $P$. Upper inset: The fitting parameter $\Gamma$ vs $P$ (circles). Also plotted is the zero-field conductance $G_0=G(0,2.2\mathrm{K},P)$ (squares). Both show a linear pressure dependence. (b) $\Delta R$ at different fields vs pressure. The solid lines are from 2DWL theory using the empirical relation between $B_{\varphi }$ and $P$ as derived in the inset of (a).