Nonlinear thermovoltage and thermocurrent in quantum dots

Svensson, Sofia Fahlvik; Hoffmann, E.; Nakpathomkun, Natthapon; Wu, Phillip M.; Xu, Hongqi; Nilsson, Henrik; Sánchez, David; Kashcheyevs, Vyacheslavs; Linke, Heiner

doi:10.1088/1367-2630/15/10/105011

Cited by 125 publications

(156 citation statements)

References 52 publications

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“…Nonlinear energy transport thus requires careful consideration: One needs a physical model allowing for charge fluctuations as well as a nonequilibrium transport theory that captures at least the first two leading orders of tunneling processes for strong interactions. Experimentally, even higher-order tunneling effects may be important [37] and it is of interest to explore renormalization effects [12,57,58]. …”

Section: O(mentioning

confidence: 99%

“…This includes the study of resonant tunneling [26], inelastic tunneling [27][28][29], and Kondo processes [30][31][32][33]. Works addressing the nonlinear regime have either applied effective single-particle descriptions [34][35][36][37][38] or focused on thermoelectric devices close to resonance assuming weak tunneling [39][40][41] or a weak Coulomb interaction [42]. The heat current has received much less attention [39][40][41][42].…”

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confidence: 99%

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Charge fluctuations in nonlinear heat transport

et al. 2015

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We show that charge fluctuation processes are crucial for the nonlinear heat conductance through an interacting nanostructure, even far from a resonance. We illustrate this for an Anderson quantum dot accounting for the first two leading orders of the tunneling in a master equation. The often made assumption that off-resonant transport proceeds entirely by virtual occupation of charge states, underlying exchange-scattering models, can fail dramatically for heat transport. The identified energy-transport resonances in the Coulomb blockade regime provide qualitative information about relaxation processes, for instance, by a strong negative differential heat conductance relative to the heat current. These can go unnoticed in the charge current, making nonlinear heat-transport spectroscopy with energy-level control a promising experimental tool. [6]. Here, by analyzing the generic effects of Coulomb interactions on the nonlinear heat transport in nanoscale systems, we will show that this is very promising.Interaction effects have long been probed using gate controlled charge-current spectroscopy, a well-developed experimental tool to access the discrete quantum levels of nanostructures. Two prominent features in the charge current driven by a source-drain voltage underpin this successful method. The first is resonant or single-electron tunneling (SET), which depends on the level position relative to the electrochemical potential, μ R in Fig. 1(a): An electron jumps into or out of an orbital level, directly leading to a real change of its occupancy. The current shows sharp steps as new resonant transport processes are switched on with increasing bias. These processes are routinely identified in a three-terminal setup by plotting the charge conductance as function of the applied bias V and the gate voltage, as exemplified in Fig. 2(a). Two-terminal measurements, e.g., using a scanning probe, correspond to line traces through such a plot. The second type of resonance is independent of the level position and appears as a horizontal line at V = since it originates in the inelastic excitation by an energy at fixed local electron number on the nanostructure. This off-resonant feature requires a second-order tunneling process in which an electron "scatters through," other charge states being only visited virtually [see Fig. 1(b)]. This is known as inelastic electron tunneling (IETS) [7,8] or inelastic cotunneling (ICOT) [9][10][11][12].This inelastic tunneling resonance develops into a nonequilibrium Kondo resonance for low and low temperatures [13][14][15], which is much sharper [11,12] Thermoelectric transport has also been investigated within the two above-mentioned physical transport pictures. Theory mostly focused on the thermopower in the linear-response regime. This includes the study of resonant tunneling [26], inelastic tunneling [27][28][29], and Kondo processes [30][31][32][33]. Works addressing the nonlinear regime have either applied effective single-particle descriptions [34][35][36][37][38] or focused on th...

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Section: O(mentioning

confidence: 99%

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confidence: 99%

Charge fluctuations in nonlinear heat transport

et al. 2015

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“…While the temperature differential between electrodes enhances, the system may shift to nonlinear regime of action. For example, a thermovoltage that nonlinearly alter with ∆θ was reported experimentally and theoretically on semiconductor quantum dots and singlemolecule junctions [42][43][44] . We focus on the charge and spin Seebeck coefficients (S ch , S sp ) and their corresponding figures of merit Z ch T andZ sp T .…”

Section: Numerical Resultsmentioning

confidence: 99%

Spin and charge thermopower effects in the ferromagnetic graphene junction

Vahedi

Barimani

2016

Journal of Applied Physics

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Using wave function matching approach and employing the Landauer-Buttiker formula a ferromagnetic graphene junction with temperature gradient across the system, is studied. We calculate the thermally induced charge and spin current as well as the thermoelectric voltage (Seebeck effect) in the linear and nonlinear regimes. Our calculation revealed that owing to the electron-hole symmetry, the charge Seebeck coefficient is, for an undoped magnetic graphene, an odd function of chemical potential while the spin Seebeck coefficient is an even function regardless of the temperature gradient and junction length. We have also found with an accurate tuning external parameter, namely the exchange filed and gate voltage, the temperature gradient across the junction drives a pure spin current without accompanying the charge current. Another important characteristic of thermoelectric transport, thermally induced current in the nonlinear regime, is examined. It would be our main finding that with increasing thermal gradient applied to the junction the spin and charge thermovoltages decrease and even become zero for non zero temperature bias.

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“…Properties of the thermovoltage in molecular junctions and quantum dots were theoretically analyzed in numerous works [20][21][22][23][24][25][26][27][28][29]. As yet, less attention was paid to studies of thermocurrent in spite of the fact that I th is more straightforward to measure and model than V th , as stated in the recent work [19]. However, theoretical analysis of I th behavior within a weakly nonlinear regime was recently suggested [25].…”

Section: Introductionmentioning

confidence: 99%

Scattering theory of thermocurrent in quantum dots and molecules

Zimbovskaya

2015

Physica E: Low-dimensional Systems and Nanostructures

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In this work we theoretically study properties of electric current driven by a temperature gradient through a quantum dot/molecule coupled to the source and drain charge reservoirs. We analyze the effect of Coulomb interactions between electrons on the dot/molecule and of thermal phonons associated with the electrodes thermal environment on the thermocurrent. The scattering matrix formalism is employed to compute electron transmission through the system. This approach is further developed and combined with nonequilibrium Green's functions formalism, so that scattering probabilities are expressed in terms of relevant energies including the thermal energy, strengths of coupling between the dot/molecule and charge reservoirs and characteristic energies of electronphonon interactions in the electrodes. It is shown that one may bring the considered system into regime favorable for heat-to-electric energy conversion by varying the applied bias and gate voltages.

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Nonlinear thermovoltage and thermocurrent in quantum dots

Cited by 125 publications

References 52 publications

Charge fluctuations in nonlinear heat transport

Charge fluctuations in nonlinear heat transport

Spin and charge thermopower effects in the ferromagnetic graphene junction

Scattering theory of thermocurrent in quantum dots and molecules

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