Thermopower of a single-electron transistor in the regime of strong inelastic cotunneling

We study Coulomb blockade oscillations of thermoelectric coefficients of a single-electron transistor based on a quantum dot strongly coupled to one of the leads by a quantum point contact. At temperatures below the charging energy E-C the transport of electrons is dominated by strong inelastic cotunneling. In this regime we find analytic expressions for the thermopower as a function of temperature T and the reflection amplitude r in the contact. In the case when the electron spins are polarized by a strong external magnetic field, the thermopower shows sinusoidal oscillations as a function of the gate voltage with the amplitude of the order of e(-1)\r\(T/E-C). We obtain qualitatively different results in the absence of the magnetic field. At temperatures between E-C and E-C\r\(2) the thermopower oscillations are sinusoidal with the amplitude of order e(-1)\r\(2)ln(E-C/T). On the other hand, at Tmuch less thanE(C)\r\(2) we find nonsinusoidal oscillations of the thermopower with the amplitude similar toe(-1)\r\rootT/E(C)ln(E-C/T).