Kondo Resonances in Molecular Devices

Abstract

Molecular electronic devices currently serve as a platform for studying a variety of physical phenomena only accessible at the nanometer scale. One such phenomenon is the highly correlated electronic state responsible for the Kondo effect, manifested here as a "Kondo resonance" in the conductance. Because the Kondo effect results from strong electron-electron interactions, it is not captured by the usual quantum chemistry approaches traditionally applied to understand chemical electron transfer. In this review we will discuss the origins and phenomenology of Kondo resonances observed in single molecule devices, focusing primarily on the spin- Kondo state arising from a single unpaired electron. We explore the rich physical system of a single-molecule device, which offers a unique spectroscopic tool for investigating the interplay of emergent Kondo behavior and such properties as molecular orbital transitions and vibrational modes. We will additionally address more exotic systems, such as higher spin states in the Kondo regime, and we will review recent experimental advances in the ability to manipulate and exert control over these nanoscale devices.

Synthesis and Characterization of a Series of Ruthenium Tris(β‐diketonato) Complexes by an UHV‐STM Investigation and Numerical Calculations

“…More generally, these results show that this type of compound can be used for experiments in which single larger Ru complexes would be studied and manipulated using the special properties of STM for potential applications in the field of quantum computation. Moreover, it opens the route to the physics of the Kondo effect on the single molecular scale, [60][61][62] in particular because of the presence of the Ru III paramagnetic centre, or to studies dedicated to the magnetic inforwww.eurjic.orgmation transfer through a molecular adlayer or molecular wire. [63][64][65] …”

Universal transport signatures in two-electron molecular quantum dots: gate-tunable Hund’s rule, underscreened Kondo effect and quantum phase transitions

“…The first observation in semiconducting quantum dots of the Kondo effect [9,10] has triggered intense experimental research to make similar observations in other physical systems such as carbon nanotubes [11] and molecular devices [12,13], see Ref. [14] for a review. In parallel, many theoretical works have followed, and at present reliable methods, such as the Numerical Renormalization Group (NRG) [15,16], have been developped.…”

“…Kondo physics has been widely reported in a variety of quantum dot systems, based on semiconducting heterostructures [9,10], carbon nanotubes [11] and molecular devices [12,13,34,18,14], showing the great universality of this phenomenon. Usually the Kondo effect is best observed for odd charge quantum dots, because the formation of a net spin S = 1/2 is always guaranteed in that case (for even charge dots, the ground state turns out often to be a non-magnetic singlet).…”

Molecular Transistors

“…van der Zant et al and Natelson et al have achieved much in this field, such as transport measurements through single molecular magnets [161], the observation of the Kondo effect in gold break junctions with the presence of magnetic impurities [162], inelastic tunneling features via molecular vibrations in the Kondo regime [163], and fundamental scaling laws that govern the nonequilibrium standard spin-1/2 Kondo effect [164]. We recommend the following reviews on this subject: References [46,47,[165][166][167].…”