**3. Results and Discussion**

As we consider the WBLA, the detailed electronic structure of the leads is not important for the description of the transport properties of the GNR. We then fix the coupling strength between the GNR and the leads by the frequency-independent resonance width *Γα* = *tC*/10 corresponding to a weak-coupling regime where the WBLA is a good approximation [44–47]. This is further justified in typical transport setups where the bandwidth of the leads is sufficiently large (e.g., gold electrodes) compared to the applied bias voltage. As we wish to preserve the charge neutrality of the GNR in equilibrium, we set the chemical potential to *μ* = 0. The global equilibrium temperature is set by (*k*B*<sup>T</sup>*)−<sup>1</sup> = 100*t* −1 *C*(*T* = 313 K).

### *3.1. Response to a dc Drive*

It is instructive to first study the current correlations in GNRs without disorder. Figure 2 shows the current cross-correlations of undisordered AGNRs and ZGNRs of various lengths and *time-independent* bias voltages. We can make many general observations from the data:


**Figure 2.** Absolute value of the current cross-correlation *C*(×) (*t* + *τ*, *t*) at long observation times *t* → ∞ for various undisordered GNR samples with varying bias voltage and the consequent Fourier spectra: (**a**) AGNR of various lengths; (**b**) ZGNR of various lengths; (**c**) the low-frequency region of the Fourier transform of (**a**) for fixed bias voltage *VL* = −*VR* = *tC*/2 (the inset shows the full frequency range); and (**d**) the low-frequency region of the Fourier transform of (**b**) for fixed bias voltage *VL* = −*VR* = *tC*/2 (the inset shows the full frequency range).
