Sequential and cotunneling behavior in the temperature-dependent thermopower of few-electron quantum dots

Abstract

We have studied the temperature dependent thermopower of gate-defined, lateral quantum dots in the Coulomb blockade regime using an electron heating technique. The line shape of the thermopower oscillations depends strongly on the contributing tunneling processes. Between 1.5 K and 40 mK a crossover from a pure sawtooth-to an intermitted sawtooth-like line shape is observed. The latter is attributed to the increasing dominance of cotunneling processes in the Coulomb blockade regime at low temperatures.

Thermopower of a Quantum Dot in a Coherent Regime

“…The sequential tunneling theory predicts a sawtooth-shaped TEP oscillation at high temperatures in a Coulomb blockade regime, 1 while co-tunneling processes are expected to suppress TEP between Coulomb blockade peaks at low temperatures. 2 These predictions have been confirmed in recent experiments of QDs fabricated in two-dimensional electron gases [3][4][5] and singlewall carbon nanotubes. 6,7 In the previous theoretical studies of TEP, only incoherent tunneling processes have been considered.…”

“…Then, the transmission coefficient becomes the difference of two Breit-Wigner line-shapes as 5) and therefore the transmission amplitude never vanishes. Reflecting the disappearance of the transmission zero, the TEP has no significant structure between the resonant peaks.…”

“…25 The Mott formula has been used widely for analysis of the TEP measurements. [3][4][5][6][7] It is derived by the Sommerfeld expansion (2.1) and (2.2) with taking up to the first order of T as…”

Thermoelectric Properties of a T-Shaped Quantum Dot with Relatively Strong On-Site Coulomb Interaction

“…The thermal power (S) exhibits a change of sign (the socalled bipolar effect) with respect to gate voltage at different temperatures (Fig. 5), consistent with the experimental results of Scheibner et al 30) and theoretical prediction in the metallic single-electron transistor. 31,32) The sign of the thermopower S could indicate the main channel of heat transportation.…”

Theory of single-electron heat engines coupled to electromagnetic environments

“…Thermoelectric properties of weakly coupled quantum dots have also been experimentally studied. [7][8][9][10] This type of device operates as a heat engine by generating electrical current and transferring heat between the same two reservoirs. A recent modification 11,12 of this scheme makes the charge and heat currents flow along different pathways by introducing a third reservoir: charge is transported between two reservoirs at the same temperature, while the third reservoir, at a different temperature, is Coulomb-coupled to the transport electrons and supplies the thermal fluctuations driving the heat engine.…”