Effect of interdot Coulomb repulsion on tunneling current through a double quantum dot system in the weak tunneling limit: Strong electron-phonon coupling

Pronounced effects of the interdot Coulomb repulsion on the tunnel current/gate voltage dependence at the ambient conditions are predicted for the double quantum dot system in the serial configuration immersed in the electrolyte solution in the case of the weak tunneling of electrons both between the dots and between the dots and leads. Electrons at the dots are coupled strongly to the classical phonon modes and Debye screening of the electric field is taken into account. The infinite intradot Coulomb repulsion limit is used. The effects consist of (i) a very large width of the maximum of the tunnel current/gate voltage dependence [of the order of -k(B)T ln(k(0)/k), where k(0) and k are the characteristic rates of the electron tunneling between the dots and between the dots and leads, respectively] in the limit k(0)/k -> 0, (ii) the dependence of the positions of the maxima of the current/gate voltage curve and their widths on the sign of the difference of the electron energy levels delta of the quantum dots and the energy of the polaron shift, and (iii) narrow-width Coulomb blockade peaks in the tunnel current/gate voltage curve for k(0) >= k. The dependence of the differential conductance on the gate voltage, the energy of the interdot Coulomb repulsion, the Debye screening length, and values of k(0)/k and delta are studied. It is shown that the curves of the differential conductance/bias voltage dependence can be very different for different values of these parameters. These parameters also determine the position of the regions of the negative differential conductance which exist in the general case.