Thermoelectric Conversion at 30 K in InAs/InP Nanowire Quantum Dots

Prete, Domenic; Erdman, Paolo Andrea; Demontis, Valeria; Zannier, Valentina; Ercolani, Daniele; Sorba, L.; Beltram, Fabio; Rossella, Francesco; Taddei, F.; Roddaro, Stefano

doi:10.1021/acs.nanolett.9b00276

Cited by 77 publications

(82 citation statements)

References 74 publications

(148 reference statements)

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“…The field B 0 , of order T K in the Kondo regime, is comparable, but quantitatively different, to the field B c for the splitting of the Kondo resonance. Our results are of relevance in the light of recent advances in characterizing the thermoelectric properties of nanodevices [20,21,35,49,59]. They explain, for example, the essential observations ( Fig.…”

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confidence: 74%

Magnetic field dependence of the thermopower of Kondo-correlated quantum dots

Costi

2019

Phys. Rev. B

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Recent experiments have measured the signatures of the Kondo effect in the zero-field thermopower of strongly correlated quantum dots [Svilans et al., Phys. Rev. Lett. 121, 206801 (2018); Dutta et al., Nano Lett. 19, 506 (2019)]. They confirm the predicted Kondo-induced sign change in the thermopower, upon increasing the temperature through a gate-voltage dependent value T 1 T K , where T K is the Kondo temperature. Here, we use the numerical renormalization group (NRG) method to investigate the effect of a finite magnetic field B on the thermopower of such quantum dots. We show that, for fields B exceeding a gate-voltage dependent value B 0 , an additional sign change takes place in the Kondo regime at a temperature T 0 (B ≥ B 0 ) > 0 with T 0 < T 1 . The field B 0 is comparable to, but larger than, the field B c at which the zero-temperature spectral function splits in a magnetic field. The validity of the NRG results for B 0 are checked by comparison with asymptotically exact higher-order Fermi-liquid calculations [Oguri et al., Phys. Rev. B 97, 035435 (2018)]. Our calculations clarify the field-dependent signatures of the Kondo effect in the thermopower of Kondo-correlated quantum dots and explain the recently measured trends in the B-field dependence of the thermoelectric response of such systems [Svilans et al., Phys. Rev. Lett. 121, 206801 (2018)]. K ≈ 0.50 where T HWHM K is the HWHM of the T = 0 Kondo resonance given by T HWHM K

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confidence: 74%

Magnetic field dependence of the thermopower of Kondo-correlated quantum dots

Costi

2019

Phys. Rev. B

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“…Quantum thermodynamics [6][7][8] has emerged both as a field of fundamental interest, and as a potential candidate to improve the performance of thermal machines [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. The optimal performance of these systems has been discussed within several frameworks and operational assumptions, ranging from low-dissipation and slow driving regimes [24][25][26][27][28], to shortcuts to adiabaticity approaches [29][30][31][32], to endoreversible engines [33,34].…”

Section: Introductionmentioning

confidence: 99%

“…In view of experimental implementations, we assess the impact of finite-time effects on our optimal protocol, finding that the maximum power does not decrease much if the external driving is not much slower than the typical dissipation rate induced by the baths [58,59]. Furthermore, we apply our optimal protocol to two experimentally accessible models, namely photonic baths coupled to a qubit [22, 60-63] and electronic leads coupled to a quantum dot [21,23,58,59,64,65].C , and Γ in (c) denotes *  G( ) H . 4 In principle, one can consider a broader family of controls including the possibility of rotating the Hamiltonian eigenvectors; however there is evidence that such an additional freedom does not help in two-level systems [45, 46].…”

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Maximum power and corresponding efficiency for two-level heat engines and refrigerators: optimality of fast cycles

et al. 2019

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We study how to achieve the ultimate power in the simplest, yet non-trivial, model of a thermal machine, namely a two-level quantum system coupled to two thermal baths. Without making any prior assumption on the protocol, via optimal control we show that, regardless of the microscopic details and of the operating mode of the thermal machine, the maximum power is universally achieved by a fast Otto-cycle like structure in which the controls are rapidly switched between two extremal values. A closed formula for the maximum power is derived, and finite-speed effects are discussed. We also analyze the associated efficiency at maximum power showing that, contrary to universal results derived in the slow-driving regime, it can approach Carnot's efficiency, no other universal bounds being allowed.'fast-driving' regime, i.e. when the driving frequency is faster than the typical dissipation rate induced by the baths, which has received little attention in literature [50][51][52].By applying our optimal protocol to heat engines and refrigerators, we find new theoretical bounds on the efficiency at maximum power (EMP). Many upper limits to the EMP, strictly smaller than Carnot's efficiency, have been derived in literature, such as the Curzon-Ahlborn and Schmiedl-Seifert efficiencies. The Curzon-Ahlborn efficiency emerges in various specific models [53][54][55], and it has been derived by general arguments from linear irreversible thermodynamics [56]. The Schmiedl-Seifert efficiency has been proven to be universal in cyclic Brownian heat engines [57] and for any driven system operating in the slow-driving regime [24]. By studying the efficiency of our system at the ultimate power, i.e. in the fast-driving regime, we prove that there is no fundamental upper bound to the EMP. Indeed, we show that the Carnot efficiency is reachable at maximum power through a suitable engineering of the bath couplings. This is our second main results, illustrated in figures 2(b), (c) and figure 3. In view of experimental implementations, we assess the impact of finite-time effects on our optimal protocol, finding that the maximum power does not decrease much if the external driving is not much slower than the typical dissipation rate induced by the baths [58,59]. Furthermore, we apply our optimal protocol to two experimentally accessible models, namely photonic baths coupled to a qubit [22, 60-63] and electronic leads coupled to a quantum dot [21,23,58,59,64,65].C , and Γ in (c) denotes *  G( ) H . 4 In principle, one can consider a broader family of controls including the possibility of rotating the Hamiltonian eigenvectors; however there is evidence that such an additional freedom does not help in two-level systems [45, 46]. ≔ [ ] ( ) J J t p t J J t p t

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“…They give additional information on the low-energy Kondo resonance, such as its position relative to the Fermi level and how the relative weight below and above the Fermi level changes with temperature and magnetic field as reflected in the sign changes discussed in this paper. Be-yond being of relevance to experiments which characterize the thermoelectric properties of nanodevices 25,26,39,40,70 , calculations along the same lines, can be carried out for classical Kondo impurities, and could be of some relevance to thermopower measurements in heavy fermions. In this paper we addressed only the linear-response thermopower (and thermocurrent).…”

Section: Discussionmentioning

confidence: 99%

Magnetic field dependence of the thermopower of Kondo-correlated quantum dots: Comparison with experiment

Costi

2019

Phys. Rev. B

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Signatures of the Kondo effect in the electrical conductance of strongly correlated quantum dots are well understood both experimentally and theoretically, while those in the thermopower have been the subject of recent interest, both theoretically and experimentally. Here, we extend theoretical work [T. A. Costi, Phys. Rev. B 100, 161106(R) (2019)] on the field-dependent thermopower of such systems to the mixed valence and empty orbital regimes, and carry out calculations in order to address a recent experiment on the field dependent thermoelectric response of Kondo-correlated quantum dots [A. Svilans et al., Phys. Rev. Lett. 121, 206801 (2018)]. In addition to the sign changes in the thermopower at temperatures T 1 (B) and T 2 (B) (present also for B = 0) in the Kondo regime, an additional sign change was found [T. A. Costi, Phys. Rev. B 100, 161106(R) (2019)] at a temperature T 0 (B) < T 1 (B) < T 2 (B) for fields exceeding a gate-voltage dependent value B 0 , where B 0 is comparable to, but larger, than the field B c at which the Kondo resonance splits. We describe the evolution of the Kondo-induced sign changes in the thermopower at temperatures T 0 (B), T 1 (B) and T 2 (B) with magnetic field and gate voltage from the Kondo regime to the mixed valence and empty orbital regimes and show that these temperatures merge to the single temperature T 0 (B) upon entry into the mixed valence regime. By carrying out detailed numerical renormalization group calculations for the above quantities, using appropriate experimental parameters, we address a recent experiment which measures the field-dependent thermoelectric response of InAs quantum dots exhibiting the Kondo effect [A. Svilans et al., Phys. Rev. Lett. 121, 206801 (2018)]. This allows us to understand the overall trends in the measured field-and temperature-dependent thermoelectric response as a function of gate voltage. In addition, we determine which signatures of the Kondo effect (sign changes at T 0 (B), T 1 (B) and T 2 (B)) have been observed in this experiment, and find that while the Kondoinduced signature at T 1 (B) is indeed measured in the data, the signature at T 0 (B) can only be observed by carrying out further measurements at a lower temperature. In addition, the less interesting (high-temperature) signature at T 2 (B) Γ, where Γ is the electron tunneling rate onto the dot, is found to lie above the highest temperature in the experiment, and was therefore not accessed. Our calculations provide a useful framework for interpreting future experiments on direct measurements of the thermopower of Kondo-correlated quantum dots in the presence of finite magnetic fields, e.g., by extending zero-field measurements of the thermopower [B. Dutta et al., Nano Lett. 19, 506 (2019)] to finite magnetic fields. arXiv:1910.08785v1 [cond-mat.str-el]

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Thermoelectric Conversion at 30 K in InAs/InP Nanowire Quantum Dots

Cited by 77 publications

References 74 publications

Magnetic field dependence of the thermopower of Kondo-correlated quantum dots

Magnetic field dependence of the thermopower of Kondo-correlated quantum dots

Maximum power and corresponding efficiency for two-level heat engines and refrigerators: optimality of fast cycles

Magnetic field dependence of the thermopower of Kondo-correlated quantum dots: Comparison with experiment

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