Correlated Adatom Trimer on a Metal Surface: A Continuous-Time Quantum Monte Carlo Study

The electronic properties and spectroscopic features of a magnetic trimer with a Kondo-like coupling to a non-magnetic metallic substrate are analyzed at zero temperature. The substrate density of states is depressed in the trimer neighbourhood, being exactly zero at the substrate chemical potential. The size of the resonance strongly depends on the magnetic state of the trimer, and exhibits a two-state behavior. The geometrical dependence of these results agree qualitatively with recent experiments and could be reproduced in a triangular quantum dot arrangement. Keywords:The combination of the Scanning Tunneling Microscope (STM), which can be used as a "tool" to build and characterize atomically-precise structures, and the availability of high-quality clean metallic surfaces has provided a unique opportunity to investigate the chemical and physical properties of deposited atoms, molecules, and clusters with unprecedented resolution. It has been natural then that much of the research concentrates on one of the old paradigms of condensed-matter physics: the behavior of magnetic impurities immersed in an otherwise non-magnetic matrix. Ground-breaking experiments have been reported on the properties of magnetic monomers[1] and dimers[2], quantum-confinement of surface two-dimensional electron gases by a "corral" of STM-positioned magnetic atoms [3], and "molecule cascade" devices[4], with potential for quantum computing. In most of these examples, it has become evident that at low-temperatures the physics of magnetic impurities on the metallic surface is dominated by the so-called Kondo effect. Historically, the Kondo effect was introduced more than forty years ago to explain the resistivity minimum for decreasing temperatures observed in metallic matrices with a minute fraction of magnetic impurities. [5] Additional interest in the Kondo effect arose recently from the semiconductor nano-oriented community, after realization[7, 8] that a quantum dot with two attached conducting leads behaves in many aspects as a magnetic atom in a metal. [9,10] The aim of this work is the theoretical study of a magnetic trimer in contact with a metallic substrate. The trimer geometry is very interesting, due to the fact that it is the simplest geometrical arrangement (including monomers and dimers) which displays magnetic frustration among the three magnetic moments for the case of antiferromagnetic interactions [11]. The main result from our work is that as a consequence of the interplay between the trimer-metal Kondo interaction which tries to stabilize the trimer in a high-spin state, and the intratrimer antiferromagnetic interactions which try of stabilize a low-spin trimer state, the whole system exhibits -2 -1 0 1 2 t' t 3 2 1 J J J J 1 J 2 J 2 FIG. 1: Schematic diagram of the system considered: an AF spin trimer Kondo-coupled to a non-interacting chaina two-state spectroscopic behavior that depends on the geometrical arrangement of the triangle (whether it is an equilateral or isosceles triangle) and on the interaction parame...

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“…separating atom number 2. Our results also agree qualitatively with recent results based on Quantum Monte Carlo calculations [18].…”

Section: Introductionsupporting

confidence: 93%

Two-state behaviour of Kondo trimers

2006

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“…We study this model at finite temperature using QMC 11,12 as impurity solver. Also, first successful attempts to apply a more demanding continuous-time QMC algorithm to a simplified two-impurity problem already exist 13 . Here, the focus is on the nature of the transition from the Mott insulator to the band insulator phase.…”

Section: Introductionmentioning

confidence: 99%

From Mott insulator to band insulator: A dynamical mean-field theory study

2006

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The question if a Mott insulator and a band insulator are fundamentally different has been the matter of intensive research recently. Here we consider a simple model which allows by tuning one parameter to go continously from a Mott insulator to band insulator. The model consists of two Hubbard systems connected by single particle hopping. The Hubbard Hamiltonian is solved by the Dynamical Mean-Field theory using Quantum Monte Carlo to solve the resulting the quantum impurity problem. The quasiparticle spectral function is calculated. Here we focus on the optical conductivity and in particular on the Drude weight which can be experimentally measured. From our calculation we conclude that there is a continous crossover from the band insulator to the Mott insulator phase at finite temperature.

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“…As the number of the nearest-neighbors for every Co atom in the Co clusters increased to above one, the interaction between the Co atoms become much stronger, and a new state forms in the dI/dV spectra in figure 5. One of reason may be similar with the disappearance of the Kondo resonance of the compact Co dimer on Au(111) and Cu(100) [17,20], when the coupling among these Co atoms in compact triangular trimer become a strong ferromagnetic exchange interaction ( J Co-Co ?T K monomer ), the Kondo temperature T K trimer ∼ (T K monomer ) 3 /J Co-Co 2 [34], so the Kondo temperature becomes much lower than the experimental temperature. Because the Kondo resonances can not be detected in these large clusters, another reason can not be excluded, it is that the Kondo effect may be suppressed completely by the strong ferromagnetic exchange interaction.…”

Section: Resultsmentioning

confidence: 87%

Preserved Kondo effect of small cobalt atomic chains on Ru(0001) surface

et al. 2016

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The evolution of the Kondo effect from a cobalt monomer to a compact dimer, a linear trimer and then a triangular trimer on Ru(0001) surface was studied by atomic manipulation and scanning tunneling spectroscopy (STS). It is found that the Kondo resonances of a compact Co dimer and linear trimer still can be detected in their STS because of the weak ferromagnetic exchange interaction between the Co atoms. However, when the number of the nearest-neighbors for every Co atom in the compact Co clusters is larger than one, for the interaction between Co atoms enter into the regime of the strong ferromagnetic exchange interaction, the Kondo resonance disappear and a new state forms.

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Correlated Adatom Trimer on a Metal Surface: A Continuous-Time Quantum Monte Carlo Study

Cited by 38 publications

References 30 publications

Two-state behaviour of Kondo trimers

Two-state behaviour of Kondo trimers

From Mott insulator to band insulator: A dynamical mean-field theory study

Preserved Kondo effect of small cobalt atomic chains on Ru(0001) surface

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