But T * and T K are not trivially related 4. The Kondo lattice introduces a new energy scale, k B T *, which plays the role of T K in the sense that below T * the magnetic susceptibility starts being anomalously reduced due to partial screening 3. In the limit of a large coupling strength, Jρ, between localized moments and extended states of the conduction electrons, the two subsystems cannot be treated separately. The AFM coupling is driven by the Ruderman-Kittle-Kasuya-Yosida (RKKY) indirect exchange interaction. 1a, c), both characterized by a finite impurity spin. When the two subsystems are weakly coupled, the Kondo lattice falls in the paramagnetic or antiferromagnetic (AFM) regimes (Fig. In the AFM state, the spin polarization of the the electron bath induced by the green and blue impurity spins is represented by a decaying oscillatory function (responsible for the RKKY exchange coupling)Ī Kondo lattice is a set of localized magnetic impurities arranged in a regular pattern, which interacts with a bath of delocalized conduction electrons. Note that in the HFL state, all impurity spins are coherently screened by all conduction electrons participating in the heavy fermion band, in contrast to the single-ion KS where each impurity spin is individually screened. For large coupling ( Jρ to the right of the QCP), the KS can be driven to the HFL phase by decreasing d, as we do in this work. For small coupling (small Jρ), the KS or the PM state can be driven to the AFM state by decreasing d or the temperature. A quantum critical point (QPC) appears at the boundary between the antiferromagnetic (AFM) and the HFL states as a function of Jρ. The role of the inter-impurity distance ( d) is described by the red wide arrow representing the dimensionless parameter k F d, where k F is the Fermi wave vector of the conduction electrons. The small black arrows represent the spins of a regular Fermi gas decoupled from the impurity spins, whereas the small coloured arrows represent the spin of conduction electrons coupled to the magnetic impurities. J is the exchange coupling between the local magnetic states (big arrows) and the Fermi gas (occupying the grey regions), and ρ the density of states of the conduction electron bath around the Fermi level. c Magnetically ordered state via RKKY interaction. b Single-ion Kondo state (KS) with non-interacting impurities. The four possible phases of a Kondo lattice: a Paramagnetic (PM) regime. Schematic phase diagram of a Kondo lattice. Since we can rule out any other interaction between Kondo impurities, this is explained in terms of the indirect hybridization of the Kondo orbitals mediated by a coherent electron gas, the mechanism that causes the emergence of heavy quasiparticles in the thermodynamic limit. It also develops enhancements at both edges of the chains. For sufficiently small interatomic separation, the spatial distribution of Kondo screening does not coincide with the position of the adatoms. Scanning tunneling spectroscopy is used to obtain maps of the Kondo resonance intensity with sub-atomic resolution. We build regularly-spaced chains of Co adatoms on a metallic surface by atomic manipulation. Here, starting from isolated magnetic impurities in the Kondo regime, we investigate the formation of the finite size analogue of a heavy Fermi liquid. The interaction among magnetic moments screened by conduction electrons drives quantum phase transitions between magnetically ordered and heavy-fermion ground states.
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