Magnetic-Field Universality of the Kondo Effect Revealed by Thermocurrent Spectroscopy

Hsu, Chunwei; Costi, T. A.; Vogel, David; Wegeberg, Christina; Mayor, Marcel; Zant, Herre S. J. van der; Gehring, Pascal

doi:10.1103/physrevlett.128.147701

Cited by 14 publications

(9 citation statements)

References 80 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The observed critical magnetic field, B c is consistent with the relation B c = 0.75k B T K /gμ B for a Landef actor, g ≈ 2. 26,27 It was also found that a small number of junctions exhibit side peaks at ±5 mV, which we attribute to the enhanced excitation of soft vibrational modes due to the Kondo interaction. 29 Next, we investigate the MR properties of several molecular junctions.…”

mentioning

confidence: 58%

“…We have observed the Kondo features from the d I /d V spectra on 44 different contacts, and T K was consistently found to be between 7 and 10 K. To further validate the presence of the Kondo effect, we analyzed the evolution of the d I /d V spectra by increasing the magnetic field up to 6 T with an increment of 1 T at a temperature of 4.2 K. The zero-bias peak starts to split prominently due to the Zeeman splitting after approximately 3.5 T, as shown in Figure b. The observed critical magnetic field, B c is consistent with the relation B c = 0.75 k B T K / gμ B for a Landé factor, g ≈ 2. , It was also found that a small number of junctions exhibit side peaks at ±5 mV, which we attribute to the enhanced excitation of soft vibrational modes due to the Kondo interaction …”

mentioning

confidence: 73%

See 1 more Smart Citation

Interplay between Magnetoresistance and Kondo Resonance in Radical Single-Molecule Junctions

et al. 2022

View full text Add to dashboard Cite

We report transport measurements on tunable single-molecule junctions of the organic perchlorotrityl radical molecule, contacted with gold electrodes at low temperature. The current−voltage characteristics of a subset of junctions shows zerobias anomalies due to the Kondo effect and in addition elevated magnetoresistance (MR). Junctions without Kondo resonance reveal a much stronger MR. Furthermore, we show that the amplitude of the MR can be tuned by mechanically stretching the junction. On the basis of these findings, we attribute the high MR to an interference effect involving spin-dependent scattering at the metal−molecule interface and assign the Kondo effect to the unpaired spin located in the center of the molecule in asymmetric junctions.

show abstract

mentioning

confidence: 58%

mentioning

confidence: 73%

Interplay between Magnetoresistance and Kondo Resonance in Radical Single-Molecule Junctions

et al. 2022

View full text Add to dashboard Cite

show abstract

“…71 A single spin-1/2 impurity that is anti-ferromagnetically coupled to a single conduction electron channel can give rise to a single channel Kondo effect. Such Kondo effect is universal and its universality has recently been verified by thermocurrent spectroscopy 72 . At high temperatures the impurity is free and acts as an unpaired spin with entropy k B ln 2).…”

Section: F Limitations Of Entropy Measurement Methodsmentioning

confidence: 80%

Electronic measurements of entropy in meso- and nanoscale systems

Pyurbeeva¹,

Mol²,

Gehring³

2022

Preprint

Self Cite

View full text Add to dashboard Cite

Entropy is one of the most fundamental quantities in physics. For systems with few degrees of freedom, the value of entropy provides a powerful insight into its microscopic dynamics, such as the number, degeneracy and relative energies of electronic states, the value of spin, degree of localisation and entanglement, and the emergence of exotic states such as non-Abelian anyons. As the size of a system decreases, the conventional methods for measuring entropy, based on heat capacity, quickly become infeasible due to the requirement of increasingly accurate measurements of heat. Several methods to directly measure entropy of mesoscopic quantum systems have recently been developed. These methods use electronic measurements of charge, conductance and thermocurrent, rather than heat, and have been successfully applied to a wide range of systems, from quantum dots and molecules, to quantum Hall states and twisted bilayer graphene. In this Review, we provide an overview of electronic direct entropy measurement methods, discuss their theoretical background, compare their ranges of applicability and look into the directions for their future extensions and applications. CONTENTS I. Introduction 1 II. Alternative entropy measurements in continuous-charge nanodevices 2 A. Thermocurrent-based method for bulk materials 3 B. Maxwell relations for entropy measurements 3 C. Charge continuity assumptions 3 III. Quantised-charge nanodevices 4 A. The effects of charge quantisation 4 B. Degeneracy effects in electrical properties of nanodevices 5 C. Thermodynamic parameters of a quantised-charge system 5 D. Maxwell relations in quantised-charge systems 6 E. Quantised-charge entropy measurement methods 6 F. Limitations of entropy measurement methods 8 IV. Current applications 9 A. Detection of non-Abelian anyons. 9 B. Twisted bilayer graphene. 9 C. Single electron transistors 9 V. Discussion and Outlook 10 VI. Conclusion 11 VII. Acknowledgements 11

show abstract

“…Particularly appealing is the symmetry of the 2,5-diaryl radical structure, as recent studies with less symmetric stable organic radicals displayed not only direct coupling of the radical to a particular electrode, but also the appearance of alternative parallel conduction pathways. 56 , 57 These background currents are troublesome as they might cloud conductance features and conductance variations originating from the population of the frontier orbitals in the different switching states. Therefore, it is important to avoid alternative conduction pathways.…”

Section: Resultsmentioning

confidence: 99%

2,5-Diaryl 6-hydroxyphenalenones for Single-Molecule Junctions

et al. 2022

Self Cite

View full text Add to dashboard Cite

A modular access to 2,5-diaryl 6-hydroxyphenalenone derivatives is developed and demonstrated by a small series of 5 molecules. Within this series, the structures 1 and 2 expose terminal methylsulfanyl anchor groups, enabling their integration in a single molecule junction. The modular synthesis is based on Suzuki cross coupling of the aryl substituents as boronic acid precursors with 5,8-dibromo-2-(tert.butyl)-4,9-dimethoxy-2,3-dihydro-1H-phenalen-1-one, and the subsequent transformation of the product to the desired 2,5-diaryl 6-hydroxyphenalenone in a reduction/deprotection sequence. The new structures are fully characterized and their optical and electrochemical properties are analysed. For the derivatives 1 and 2 suitable for single molecule junctions, the corresponding oxophenalenoxyl radicals 1R and 2R were obtained by oxidation and analysed by EPR-spectroscopy. Preliminary mechanical break junction experiments with 1 display the structure’s ability to form transient single molecule junctions. The intention behind the molecular design is to profit from the various redox states of the structure (including the neutral radical) as molecular switch in an electro-chemically triggered single molecule transport experiment.

show abstract

Magnetic-Field Universality of the Kondo Effect Revealed by Thermocurrent Spectroscopy

Cited by 14 publications

References 80 publications

Interplay between Magnetoresistance and Kondo Resonance in Radical Single-Molecule Junctions

Interplay between Magnetoresistance and Kondo Resonance in Radical Single-Molecule Junctions

Electronic measurements of entropy in meso- and nanoscale systems

2,5-Diaryl 6-hydroxyphenalenones for Single-Molecule Junctions

Contact Info

Product

Resources

About