Thermoelectrics with Coulomb-coupled quantum dots

Abstract

In this article we review the thermoelectric properties of three terminal devices with Coulomb coupled quantum dots (QDs) as observed in recent experiments [1,2]. The system we consider consists of two Coulomb-blockade QDs one of which can exchange electrons with only a single reservoir (heat reservoir) while the other dot is tunnel coupled to two reservoirs at a lower temperature (conductor). The heat reservoir and the conductor interact only via the Coulomb-coupling of the quantum dots. It has been found that two regimes have to be considered. In the first one heat flow between the two systems is small. In this regime thermally driven occupation fluctuations of the hot QD modify the transport properties of the conductor system. This leads to an effect called thermal gating. Experiment have shown how this can be used to control charge flow in the conductor by means of temperature in a remote reservoir. We further substantiate the observations with model calculations and implications for the realization of an all-thermal transistor are discussed. In the second regime, heat flow between the two systems is relevant. Here the system works as a nano scale heat engine, as proposed recently [3]. We review the conceptual idea, its experimental realization and the novel features arising in this new kind of thermoelectric device such as decoupling of heat and charge flow.

Single-electron thermal devices coupled to a mesoscopic gate

“…a thermal transistor, requires the suppression of such contributions. For example, reducing the transparency N G G reduces J G , leaving the clover leaf structure almost unaffected [84]. This is an indication that based on fluctuations of the gate only one can have a thermal gating effect, in principle involving no heat injection into the conductor.…”

Thermoelectrics in Coulomb-coupled quantum dots: Cotunneling and energy-dependent lead couplings

“…3(c), the cooling of System 1 is seen to be at the cost of heating System 2. This Coulomb-mediated energy exchange between the two QD systems occurs in spite of the fact that no electrons are exchanged, and it is the driving force behind demon-induced cooling [9,10], energy harvesting [4,8,11,12], and Coulomb drag [26,27].…”

“…The experimental progress in the control of single-electron transport [1] has spurred interest in nanosystems that utilize the associated heat currents for thermoelectric applications [2][3][4]. In particular, experiments with Coulomb-coupled quantumdot (CCQD) systems have demonstrated a plethora of phenomena ranging from Coulomb drag [5,6] and electron pairing [7] to extraordinary thermoelectric effects [8,9].…”

“…1 for the case of two Coulomb-coupled QDs). The strong interaction can be utilized to tailor the thermoelectric properties of CCQD systems [4,14], and it provides the opportunity to test fundamental thermodynamic aspects of heat transport in interacting nanoscale systems driven out of equilibrium [15].…”

Analytic treatment of the thermoelectric properties for two coupled quantum dots threaded by magnetic fields

“…Most important, we show that the magnetic flux increases also the performance of the device under maximum power output conditions. It is worth noticing that in addition to the numerous papers dealing with two quantum dots tunnel-coupled to the leads and between themselves, also Coulomb-coupled quantum dots [24,25] have attracted increasing interest in the recent years [for a general perspective see [26]. This has been motivated by the advances in the fabrication of nano-devices, energy harvesting [22] with quantum dots, and the experimental possibility to taylor TE properties exploiting Coulomb interaction and the charge carriers correlation [27].…”