a b s t r a c tStrongly correlated Fermi systems are fundamental systems in physics that are best studied experimentally, which until very recently have lacked theoretical explanations. This review discusses the construction of a theory and the analysis of phenomena occurring in strongly correlated Fermi systems such as heavy-fermion (HF) metals and two-dimensional (2D) Fermi systems. It is shown that the basic properties and the scaling behavior of HF metals can be described within the framework of a fermion condensation quantum phase transition (FCQPT) and an extended quasiparticle paradigm that allow us to explain the non-Fermi liquid behavior observed in strongly correlated Fermi systems. In contrast to the Landau paradigm stating that the quasiparticle effective mass is a constant, the effective mass of new quasiparticles strongly depends on temperature, magnetic field, pressure, and other parameters. Having analyzed the collected facts on strongly correlated Fermi systems with quite a different microscopic nature, we find these to exhibit the same non-Fermi liquid behavior at FCQPT. We show both analytically and using arguments based entirely on the experimental grounds that the data collected on very different strongly correlated Fermi systems have a universal scaling behavior, and materials with strongly correlated fermions can unexpectedly be uniform in their diversity. Our analysis of strongly correlated systems such as HF metals and 2D Fermi systems is in the context of salient experimental results. Our calculations of the non-Fermi liquid behavior, the scales and thermodynamic, relaxation and transport properties are in good agreement with experimental facts.

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Total and Mulholland partial cross sections for the elastic scattering of electrons from the lanthanide atoms lanthanum to lutetium are calculated for the electron impact energy range 0 ഛ E ഛ 1 eV. The recently developed Regge-pole methodology, which naturally embodies the crucial electron correlation effects together with a Thomas-Fermi-type potential incorporating the vital core-polarization interaction are used for the calculations. Dramatically sharp resonances are found to characterize the near-threshold electron elastic scattering total and Mulholland partial cross sections, whose energy positions are identified with the electron affinities ͑EA's͒ of these atoms through a close scrutiny of the imaginary part of the complex angular momentum. The unambiguous extracted EA values of the lanthanide atoms vary from a low value of 0.016 eV for the Tm atom to a high value of 0.631 eV for the Pr atom; none is predicted to have a lower EA value than the former. All the negative ions of the lanthanide atoms can be classified through their binding energies ͑BE's͒ as weakly bound negative ions ͑BE's Ͻ1.0 eV͒, while only three qualify to be classified as tenuously bound ͑BE'Ͻ0.1 eV͒. Ramsauer-Townsend minima, shape resonances, and the Wigner threshold behavior for these lanthanides are also determined. Comparisons of the present calculated EA's with those from various experimental measurements and other theoretical calculations are presented and discussed. In particular, our extracted EA value for the complicated open d-and f-subshell Ce atom agrees excellently with the most recently measured ͓Walter et al., Phys. Rev. A 76, 052702 ͑2007͔͒ and calculated values, while for Nd and Eu the agreement with the latest calculated values of O'Malley and Beck ͓Phys. Rev. A 77, 012505 ͑2008͒; Phys. Rev. A 78, 012510 ͑2008͔͒ is outstanding. These agreements give great credence to the already demonstrated predictive power of the Regge-pole methodology to extract unambiguous and reliable binding energies for tenuously bound and complicated open-shell negative ionic systems, requiring no a priori knowledge of the EA values whatsoever. This new perspective to the EA determination of atoms from low-energy electron elastic scattering resonances promises far-reaching implications for future accurate and reliable theoretical EA values, even for small molecules and clusters.

We consider a system trapped in a resonance state, whose decay at zero scattering angle can be related, through the optical theorem, to the total cross section ͑TCS͒. We show that for the resonance to contribute to the TCS a peak structure the resonance conditions must be satisfied: ͑i͒ Several rotations of the complex ͑the Regge trajectory-viz., imaginary part versus the real part of the complex angular momentum-stays close to the real axis͒ and ͑ii͒ coherent addition of forward-scattering subamplitudes ͑the real part of the Regge pole is close to an integer͒. We exploit the recent complex angular momentum approach of Macek et al. ͓Phys. Rev. Lett. 93, 183203 ͑2004͔͒, used to analyze low-energy oscillations observed in the elastic TCS for proton-H scattering, for a detailed analysis of Regge trajectories and their contributions to the TCS in electron-atom scattering for the case of Z = 75 using the model Thomas-Fermi potential. We conclude by demonstrating through comparison with existing theory and measurements that the Thomas-Fermi potential when used with the appropriate parameters captures the essential physics ͑Ramsauer-Townsend minima and the Wigner threshold law͒ in the near-threshold e-Ar and e-Kr elastic scattering.

Strongly correlated Fermi systems are among the most intriguing and fundamental systems in physics, whose realization in some compounds is still to be discovered. We show that herbertsmithite ZnCu3(OH)6Cl2 can be viewed as a strongly correlated Fermi system whose low temperature thermodynamic in magnetic fields is defined by a quantum critical spin liquid. Our calculations of its thermodynamic properties are in good agreement with recent experimental facts and allow us to reveal their scaling behavior which strongly resembles that observed in HF metals and 2D 3 He. An explanation of the rich behavior of strongly correlated Fermi systems still continues to be among the main problems of the condensed matter physics. One of the most interesting and puzzling issues in the research of strongly correlated Fermi systems is the non-Fermi liquid (NFL) behavior detected in their thermodynamic properties. Under the application of external fields, e.g. magnetic field B, the system can be driven to a Landau Fermi liquid behavior (LFL). Such a behavior was observed in quite different objects such as heavy-fermion (HF) metals [1, 2] and two-dimensional 3 He [2-5] Recently the herbertsmithite ZnCu 3 (OH) 6 Cl 2 has been exposed as a S = 1/2 kagome antiferromagnet [6] and new experimental investigations have revealed its unusual behavior [7][8][9]. Because of the electrostatic environment, Cu 2+ is expected to occupy the distorted octahedral kagome sites. Magnetic kagome planes Cu 2+ S = 1/2 are separated by nonmagnetic Zn 2+ layers. Observations have found no evidence of long range magnetic order or spin freezing down to temperature of 50 mK, indicating that ZnCu 3 (OH) 6 Cl 2 is the best model found of quantum kagome lattice [7][8][9][10]. The specific heat C, arising from the Cu spin system, at T < 1 K appears to be governed by a power law with an exponent which is less than or equal to 1. At the lowest explored temperature, namely over the temperature range 106 < T < 400 mK, C follows a linear law temperature dependence, C ∝ T , and for temperatures of a few Kelvin and higher, the specific heat becomes C(T ) ∝ T 3 and is dominated by the lattice contribution [7][8][9]. At low temperatures T ≤ 1, the strong magnetic field dependence of the specific heat C suggests that C is predominately magnetic in origin [7][8][9]. There are a number of papers suggesting that the S = 1/2 model on the kagome lattice can be viewed as the gapless critical spin liquid [7][8][9][13][14][15][16]. These facts allow us to test both the NFL and LFL behavior of ZnCu 3 (OH) 6 Cl 2 and to show that a Fermi quantum spin liquid formed in the herbertsmithite determines its low temperature thermodynamic properties.Contrary to the C ∝ T behavior [7,8], the observed spin liquids contribute a T 2 specific heat which in the model is not sensitive to an applied magnetic field [15,16]. Moreover the magnetic susceptibility χ(T ) of ZnCu 3 (OH) 6 Cl 2 shown in Fig.

Exotic quantum spin liquid (QSL) is formed with such hypothetic particles as fermionic spinons carrying spin 1/2 and no charge. Here we calculate its thermodynamic and relaxation properties. Our calculations unveil the fundamental properties of QSL, forming strongly correlated Fermi system located at a fermion condensation quantum phase transition. These are in a good agreement with experimental data and allow us to detect the behavior of QSL as that observed in heavy fermion metals. We predict that the thermal resistivity of QSL under the application of magnetic fields at fixed temperature demonstrates a very specific behavior. The key features of our findings are the presence of spin-charge separation and QSL formed with itinerant heavy spinons in herbertsmithite.

The interplay between Regge resonances and Ramsauer-Townsend minima in the electron elastic total cross sections for Au and Pd atoms along with their large electron affinities is proposed as the fundamental atomic mechanism responsible for the observed exceptional catalytic properties of Au nanoparticles and to explain why the combination Au-Pd possesses an even higher catalytic activity than Au or Pd separately when catalyzing H 2 O 2 , consistent with recent experiments. The investigation uses the recent complex angular momentum description of electron scattering from neutral atoms and the proposed mechanism in general.

A. Multielectron Correlation Effects in Collisions A.1. Probing Correlations through Spin-Orbit InteractionRecently, a new aspect of interchannel coupling has been found [1], known as spin-orbit activated interchannel coupling, stimulated by an experimental study on photoionization of Xe in the vicinity of the 3d threshold. This effect results only through the spin-orbit splitting of innershell thresholds. Effects of spin-orbit activated interchannel coupling on nondipole [2] photoelectron angular distribution asymmetry parameters have been discussed, including the spin-polarization of photoelectrons from 3d electrons of Xe, Cs and Ba, concluding that through spin-orbit interaction polarization can be achieved and correlation probed.Public reporting burden for this collection of information is estimated to average 1 hour per response, including ii is, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send'