Optical and transport properties of heavy fermions: theory compared to experiment

Vidhyadhiraja, N. S.; Logan, David E.

doi:10.1088/0953-8984/17/19/010

Cited by 29 publications

(43 citation statements)

References 49 publications

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“…The concepts developped here open also a new insight in the physics of correlated systems. Indeed recent studies of some heavy fermions or polaronic systems [6,7,8], where charge carriers are also slow, show that their conduction properties present a deep analogy with those described here. In particular a transition is observed from a metallic like regime at low temperature (weak scattering) to an insulating like regime at higher temperature (stronger scattering).…”

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confidence: 62%

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Quantum Transport of Slow Charge Carriers in Quasicrystals and Correlated Systems

2006

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We show that the semi-classical model of conduction breaks down if the mean free path of charge carriers is smaller than a typical extension of their wavefunction. This situation is realized for sufficiently slow charge carriers and leads to a transition from a metallic like to an insulating like regime when scattering by defects increases. This explains the unconventional conduction properties of quasicrystals and related alloys. The conduction properties of some heavy fermions or polaronic systems, where charge carriers are also slow, present a deep analogy.PACS numbers: 72.10. Bg, 61.44.Br, 71.23.Ft The semi-classical Bloch-Boltzmann theory, which plays a fundamental role in our understanding of conduction in solids, has limitations such as for example magnetic and electric breakdown [1] or quantum interferences in the diffusive regime [2] that are well known and have been intensively studied. The present work focuses on another limitation that has received little attention and that occurs when charge carriers have sufficiently small velocities.Indeed the semi-classical theory of conduction in crystals is based on the concept of a charge carrier wavepacket propagating at a velocity V = (1/ )∂E n (k)/∂k, where "E n (k)" is the dispersion relation for band n and wavevector k. The validity of the wave-packet concept requires that the extension L wp of the wave-packet of the charge carrier is smaller than the distance V τ of traveling between two scattering events separated by a time τ . On the contrary, if V τ < L wp , a condition that can be realized by sufficiently slow charge carriers, the semi-classical model breaks down. Here we report on a quantum theory that allows to treat on the same footing the standard regime where the semi-classical approach is valid and the regime of slow charge carriers. We find that when the scattering time τ decreases a transition can occur between a metallic regime for V τ > L wp and an insulating like regime for V τ < L wp . As an example we consider specifically a complex metallic alloy: the α-AlMnSi phase. Ab-initio band structure calculations show that the samples of this system, that have been studied experimentally, are in the small velocity regime V τ < L wp . This explains their unconventional conduction properties. The α-AlMnSi phase is structurally related to the icosahedral quasicrystalline phase AlMnSi and shares many similar conduction properties with other icosahedral phases such as AlCuFe and AlPdMn and their crystalline approximants [3,4,5]. Thus the present work is relevant for these systems too and gives a strong insight in the so far unexplained properties of this class of materials. The concepts developped here open also a new insight in the physics of correlated systems. Indeed recent studies of some heavy fermions or polaronic systems [6,7,8], where charge carriers are also slow, show that their conduction properties present a deep analogy with those described here. In particular a transition is observed from a metallic like regime at low temperature (we...

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confidence: 62%

“…Within a Dynamical Mean Field Theory (DMFT) calculation [24] a disappearance of the Drude peak in the incoherent regime i.e. above T * is predicted [6]. Recent theoretical results for the small polaron problem, with narrow polaronic band and thus small velocity, have been obtained also with the DMFT.…”

Section: Jean-pierre Julien and Didier Mayoumentioning

confidence: 91%

Quantum Transport of Slow Charge Carriers in Quasicrystals and Correlated Systems

2006

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“…A practical implementation of the LMA involves fixing x = 1 2 U |μ| and e i 16,42,43,50,58,62 . The current nature of the problem, however, requires us to fix the bare parameters of the single impurity Anderson model, namely, U and ǫ i .…”

Section: Inclusion Of Spin-flip Scattering Dynamicsmentioning

confidence: 99%

Local theory for Mott-Anderson localization

et al. 2016

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The paramagnetic metallic phase of the Anderson-Hubbard model (AHM) is investigated using a non-perturbative local moment approach within the framework of dynamical mean field theory with a typical medium. Our focus is on the breakdown of the metallic phase near the metal-insulators transition as seen in the single-particle spectra, scattering rates and the associated distribution of Kondo scales. We demonstrate the emergence of a universal, underlying low energy scale, T peak K . This lies close to the peak of the distribution of Kondo scales obtained within the metallic phase of the paramagnetic AHM. Spectral dynamics for energies, ω T peak K display Fermi liquid universality crossing over to an incoherent universal dynamics for ω ≫ T peak K in the scaling regime. Such universal dynamics indicate that within a local theory the low to moderately low energy physics is governed by an effective, disorder renormalised Kondo screening.

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“…From an earlier study [21], it is known that the HF system CeB 6 , belongs to the moderately strong coupling regime. Hence we have taken the theoretical results to compare with experiments on CeB 6 for the following parameters: U = 2.4t * , ǫ c = 0.5t * , η → 0 and V 2 = 0.2t 2 * .…”

Section: Comparison To Cebmentioning

confidence: 99%

Magnetoresistance in paramagnetic heavy fermion metals

Parihari

Vidhyadhiraja

2009

J. Phys.: Condens. Matter

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A theoretical study of magnetic field (h) effects on single-particle spectra and the transport quantities of heavy fermion metals in the paramagnetic phase is carried out. We have employed a non-perturbative local moment approach (LMA) to the asymmetric periodic Anderson model within the dynamical mean field framework. The lattice coherence scale ω(L), which is proportional within the LMA to the spin-flip energy scale, and has been shown in earlier studies to be the energy scale at which crossover to single-impurity physics occurs, increases monotonically with increasing magnetic field. The many body Kondo resonance in the density of states at the Fermi level splits into two, with the splitting being proportional to the field itself. For h≥0, we demonstrate adiabatic continuity from the strongly interacting case to a corresponding non-interacting limit, thus establishing Fermi liquid behaviour for heavy fermion metals in the presence of a magnetic field. In the Kondo lattice regime, the theoretically computed magnetoresistance is found to be negative in the entire temperature range. We argue that such a result could be understood at [Formula: see text] by field-induced suppression of spin-flip scattering and at [Formula: see text] through lattice coherence. The coherence peak in the heavy fermion resistivity diminishes and moves to higher temperatures with increasing field. Direct comparison of the theoretical results to the field dependent resistivity measurements in CeB(6) yields good agreement.

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Optical and transport properties of heavy fermions: theory compared to experiment

Cited by 29 publications

References 49 publications

Quantum Transport of Slow Charge Carriers in Quasicrystals and Correlated Systems

Quantum Transport of Slow Charge Carriers in Quasicrystals and Correlated Systems

Local theory for Mott-Anderson localization

Magnetoresistance in paramagnetic heavy fermion metals

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