Journal Article

FZJ-2019-05091

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Magnetic field dependence of the thermopower of Kondo-correlated quantum dots: Comparison with experiment

Costi, T. (Corresponding author)FZJ*

2019
Inst. Woodbury, NY

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Please use a persistent id in citations: http://hdl.handle.net/2128/23104  doi:10.1103/PhysRevB.100.155126

Abstract: 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 (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 T1(B) and T2(B) (present also for B=0) in the Kondo regime, an additional sign change was found [T. A. Costi, Phys. Rev. B (to be published)] at a temperature T0(B)<T1(B)<T2(B) for fields exceeding a gate-voltage-dependent value B0, where B0 is comparable to, but larger than, the field Bc at which the Kondo resonance splits. We describe the evolution of the Kondo-induced sign changes in the thermopower at temperatures T0(B),T1(B), and T2(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 T0(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 T0(B),T1(B), and T2(B)] have been observed in this experiment, and find that while the Kondo-induced signature at T1(B) is indeed measured in the data, the signature at T0(B) can only be observed by carrying out further measurements at a lower temperature. In addition, the less interesting (high-temperature) signature at T2(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.

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Contributing Institute(s):

1. Theoretische Nanoelektronik (IAS-3)
2. JARA - HPC (JARA-HPC)

Research Program(s):

1. 142 - Controlling Spin-Based Phenomena (POF3-142) (POF3-142)
2. Application of the (time-dependent) numerical renormalization group approach to thermoelectric properties of (driven) quantum dots and to time-resolved spectroscopy of correlated materials (jiff23_20181101) (jiff23_20181101)

Appears in the scientific report 2019

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Database coverage:
; ; ; Clarivate Analytics Master Journal List ; Current Contents - Physical, Chemical and Earth Sciences ; Ebsco Academic Search ; IF < 5 ; JCR ; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Web of Science Core Collection

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