Low-frequency noise in tunneling through a single spin

We propose measurements of low-frequency noise in the tunneling current through a single molecule with a spin as an experimental probe for identifying a mechanism of the spin-dependent tunneling. A specific tail near the zero frequency in the noise spectrum is predicted; the amplitude and the width being of the same order of magnitude as the recently reported peak in the noise spectrum at the spin Larmor frequency. The ratio of the spectrum amplitudes at zero- and Larmor frequencies is shown to be a convenient tool for testing theoretical predictions.

Figure 1

Schematics of the physical system. The electronic tunneling current is established by a dc voltage $V$.

Figure 2

Skeleton diagrams for calculation of the low-frequency noise. The wavy line corresponds to the correlation function ${⟨\delta S_z^2⟩}_{\omega }$.

Figure 3

Schematic diagrams for calculation of ${⟨\delta S^2⟩}_{\omega }$. Dashed lines represent auxiliary fermions, while the vertices $S_z$ and $S_x$ represent the tunneling amplitudes $T_{RL}^{\left(\mathrm{ex}\right)}{\sigma }_z$ and $T_{RL}^{\left(\mathrm{ex}\right)}{\sigma }_x$, respectively.