Thermovoltage in quantum dots with attractive interaction

Abstract

We study the linear and nonlinear thermovoltage of a quantum dot with effective attractive electron-electron interaction and weak, energydependent tunnel coupling to electronic contacts. Remarkably, we find that the thermovoltage shows signatures of repulsive interaction, which can be rationalized. These thermovoltage characteristics are robust against large potential and temperature differences well into the nonlinear regime, which we expect can be demonstrated in current state-of-the-art experiments. Furthermore, under nonlinear operation, we find extended regions of large power production at efficiencies on the order of the Curzon-Ahlborn bound interrupted only by a characteristic sharp dip.

Fermionic duality: General symmetry of open systems with strong dissipation and memory

“…[10,16] for further discussion of these assumptions and the derivation and to Refs. [10,[13][14][15][16][17]62] for numerous detailed illustrations of how the duality can be technically applied and physically exploited in the weak coupling limit.…”

“…This is much simpler and, moreover, preserves the compactness of analytical expressions already obtained. For models only slightly more complicated than the resonant level this already leads to significant simplifications and some surprising insights as shown in the weak coupling limit [10,[15][16][17].…”

“…In the following we will denote this direct consideration of the exact propagator Π(t) as approach (i) to duality. Applied to weakly coupled but locally interacting open systems, the fermionic duality (3) has already provided several interesting insights and predictions [10,[15][16][17]. For example, the time-dependent response of a "kicked" quantum dot with repulsive Coulomb interaction was shown to exhibit effects of electron-attraction.…”

“…In all these cases, the original system is analyzed by a dual system, an effective system with at worst unconventional properties. Conversely, it was also shown that the response of a physically attractive dual system can be understood better by exploiting its repulsive original system [17]. Thus in the weak-coupling limit the duality can also be used in reverse.…”

“…By a simple substitution of parameters it allows one to bypass very complicated and nonintuitive algebra. The ultimate importance of fermionic duality lies therein that this simplification allows the analysis of physical effects [10,[15][16][17] to be pushed much further. Unlike doing algebra, solution by parameter substitution has the advantage that it preserves the compact form of an expression that has already been calculated, simplified and physically well-understood.…”