Three-terminal thermoelectric transport through a molecular junction

The thermoelectric transport through a molecular bridge is discussed with an emphasis on the effects of inelastic processes of the transport electrons caused by the coupling to the vibrational modes of the molecule. In particular, it is found that when the molecule is strongly coupled to a thermal bath of its own, which may be at a temperature different from those of the electronic reservoirs, a heat current between the molecule and the electrons can be converted into an electric current. Expressions for the transport coefficients governing this conversion and similar ones are derived, and a possible scenario for increasing their magnitudes is outlined.

Figure 1

(Color online) A three-terminal system, modeled by a resonant level attached to two electronic reservoirs, having different chemical potentials and temperatures ${\mu }_{\text{L},\text{R}}$ and $T_{\text{L},\text{R}}$, respectively. An electron residing on the level interacts with its vibrational modes. The population of these phonons can be determined by the transport electrons (a “floating molecule”) or by a coupling to a phonon source kept at temperature $T_{\text{P}}$.

Figure 2

(Color online) The coefficient $S^{\text{P}}$, Eq. (42), as a function of $\beta {\omega }_0$ for $\beta {\Gamma }_{\text{L}}=0.2$ (thin line), $\beta {\Gamma }_{\text{L}}=1$ (dashed line), and $\beta {\Gamma }_{\text{L}}=5$ (dotted line). Left panel, ${\Gamma }_{\text{R}}={\Gamma }_{\text{L}}$, right panel ${\Gamma }_{\text{R}}=0.7{\Gamma }_{\text{L}}$ [see Eqs. (43, 44)]. The total bandwidth is determined by $\beta {\omega }_c=-\beta {\omega }_v=100$.