Fabry-Pérot Oscillations in Correlated Carbon Nanotubes

We report the observation of an intriguing behavior in the transport properties of nanodevices operating in a regime between the Fabry-Pérot and the Kondo limits. Using ultrahigh quality nanotube devices, we study how the conductance oscillates when sweeping the gate voltage. Surprisingly, we observe a fourfold enhancement of the oscillation period upon decreasing temperature, signaling a crossover from single-electron tunneling to Fabry-Pérot interference. These results suggest that the Fabry-Pérot interference occurs in a regime where electrons are correlated. The link between the measured correlated Fabry-Pérot oscillations and the SU(4) Kondo effect is discussed.

Figure 1

Schematics of the device and low-temperature transport characteristics. (a) The three-terminal device with a suspended CNT contacted to source ($S$), drain ($D$), and gate ($G$) electrodes. (b) Gate voltage dependence of the conductance at zero-source-drain voltage of device I at $T=15\mathrm{mK}$. An oscillating voltage with amplitude smaller than $k_{B}T/e$ is applied to measure the differential conductance.

Figure 2

Temperature-induced crossover from an interference-dominated to a charging-controlled regime in device I. (a),(b) Oscillations of the conductance $G_{\mathrm{diff}}$ versus gate voltage $V_g$ in the hole- and electron-doped regimes. (c) Evolution of the oscillation period for a series of different temperatures. The range of $V_g$ shown in this figure is highlighted in panel (a) by a dashed rectangle. (d) Temperature dependence of the conductance associated with a peak and a dip, as indicated by arrows in (c). (e) Fast Fourier transform (FFT) of the $G_{\mathrm{diff}}(V_g)$ traces at 15 mK and 8 K measured for $V_g$ between -1.0 V and -0.3 V. (f) Temperature dependence of the FFT amplitude associated with the $4e/C_g$ period oscillations and the $e/C_g$ period oscillations.

Figure 3

Measurements on device II. (a) Conductance traces for a series of different temperatures. (b) Temperature dependence of the FFT amplitude associated with the $4e/C_g$ and the $e/C_g$ period oscillations. (c) Conductance traces for different perpendicular magnetic fields at 15 mK. (d) Peak splitting as a function of magnetic field for the conductance peaks at different gate voltages.

Figure 4

From Fabry-Pérot patterns to blurred Coulomb diamonds in device I. (a) Map of the differential conductance as a function of $V_{\mathrm{sd}}$ and $V_g$ at 15 mK. From the position of the arrow, the single-particle excitation energy is extracted. (b) Differential conductance traces for a series of different source-drain voltages at 15 mK. (c) Source-drain voltage dependence of the FFT amplitude associated with the $4e/C_g$ and the $e/C_g$ period oscillations at 15 mK. The curves are obtained by doing a FFT of the $G_{\mathrm{diff}}(V_g)$ trace for each $V_{\mathrm{sd}}$ value. (d) A map of the differential conductance as a function of $V_{\mathrm{sd}}$ and $V_g$ at 8 K. The dashed lines highlight the contours of the Coulomb diamonds.