Interactions and thermoelectric effects in a parallel-coupled double quantum dot

Abstract

We investigate the nonequilibrium transport properties of a double quantum dot system connected in parallel to two leads, including intradot electron-electron interaction. In the absence of interactions the system supports a bound state in the continuum. This state is revealed as a Fano antiresonance in the transmission when the energy levels of the dots are detuned. Using the Keldysh nonequilibrium Green's function formalism, we find that the occurrence of the Fano antiresonance survives in the presence of Coulomb repulsion. We give precise predictions for the experimental detection of bound states in the continuum. First, we calculate the differential conductance as a function of the applied voltage and the dot level detuning and find that crossing points in the diamond structure are revealed as minima due to the transmission antiresonances. Second, we determine the thermoelectric current in response to an applied temperature bias. In the linear regime, quantum interference gives rise to sharp peaks in the thermoelectric conductance. Remarkably, we find interaction induced strong current nonlinearities for large thermal gradients that may lead to several nontrivial zeros in the thermocurrent. The latter property is especially attractive for thermoelectric applications.

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

“…Since then nanoscale thermoelectricity has been addressed by an increasing number of theoretical and experimental works; a perspective of the field can be found in the focus point collection in [2] and in the articles appeared in [3]. In particular, interference Ahronov-Bohm [4][5][6][7], Fano [8][9][10][11], Dicke [12,13] and Mach-Zehnder [14,15] effects, inter-and intra-dot correlation effects [16][17][18], coherent transport modification by external magnetic fields and gate voltages. [19][20][21], have been exploited to control the performance of thermoelectric heat devices.…”

Reversal of Thermoelectric Current in Tubular Nanowires

“…In these examples the charge carriers are electrons and the sign change of the thermopower means that they travel from the cold side to the hot side, which may appear counterintuitive. Other nonlinear effects can occur if the characteristic relaxation length of electrons and or phonons exceeds the sample size [10], because the energy of electrons and/or phonons is no longer controlled by the temperature of the bath, but by the generated electric bias, including Coulomb interactions [11,12].Observing such negative thermopower at the nanoscale is difficult for at least two reasons: the currents tend to be small and it is hard to maintain a constant temperature difference across such short distances. Here we argue that a generic class of tubular nanowires, to be defined in more detail below, are ideal systems for both realizing and observing negative thermopower.…”

Spin-dependent heat and thermoelectric currents in a Rashba ring coupled to a photon cavity

“…(8). In nanoscale systems coupled to electron reservoirs with zero bias window, the heat current takes on zero or positive values depending on the location of the chemical potential of the leads with respect to the energy states of the system.…”

“…Traditionally, thermal transport can be obtained by a temperature gradient across a system that contains mobile charge, which in turn create a thermoelectric current (TEC) [4]. Detailed experimental and theoretical tests have provided new insight into the thermoelectrics of low dimensional structures such as quantum dots [5,6,7], double quantum dots [8], quantum point contacts [9,10], quantum wires [11], and quantum rings [12,13]. These nano-structures show that high thermoelectric efficiency may be achieved by using the quantum properties of the systems [1], such as quantized energy [14], and interference effects [15].…”