Electronic structure in the Al-Mn alloy crystalline analog of quasicrystals

Fujiwara, Takeo

doi:10.1103/physrevb.40.942

Cited by 224 publications

(128 citation statements)

References 15 publications

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“…2, the total DOS n of the α-AlMnSi phase is presented versus the energy. Its total density of states is characterized [14] by a depletion near the Fermi energy E F , called pseudo-gap, which is observed experimentally. This is due to a Hume-Rothery mechanism [13,17] of band energy minimization that is strong in quasicrystals and their approximants [17].…”

Section: Jean-pierre Julien and Didier Mayoumentioning

confidence: 99%

“…), cubic Al 12 Mn [13] and orthorhombic Al 6 Mn [13] crystals, which have a metallic behavior. For all those systems, the electronic structure calculation have been performed [13,14,15] by using the self-consistent Tight-Binding Linear Muffin Tin orbital (TB-LMTO) method [16]. Starting from the computed eigenstates |n k , we use equations (3)and (4) to compute the velocity correlation function without disorder, C(E, t) and the square of the spreading ∆X 2 (E, t).…”

Section: Jean-pierre Julien and Didier Mayoumentioning

confidence: 99%

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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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Section: Jean-pierre Julien and Didier Mayoumentioning

confidence: 99%

Section: Jean-pierre Julien and Didier Mayoumentioning

confidence: 99%

Quantum Transport of Slow Charge Carriers in Quasicrystals and Correlated Systems

2006

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“…The LMTO density of states (DOS) of an α-AlMn idealized approximant (structural model of Elser-Henley [19]) has been first calculated by T. Fujiwara [12,20]. This original work shows the presence of a HumeRothery pseudo-gap near the Fermi energy, E F , in agreement with experimental results [7,11].…”

Section: Results: Density Of Statessupporting

confidence: 74%

Ab-Initio Quantum Diffusion in Quasicrystals

Julien¹,

Laissardière

Mayou³

Recent Advances in the Theory of Chemical and Physical Systems

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Abstract. We compute the velocity correlation function of electronic states close to the Fermi energy, in approximants of quasicrystals. As we show the long time value of this correlation function is small. This means a small Fermi velocity, in agreement with previous band structure studies. Furthermore the correlation function is negative on a large time interval which means a phenomenon of backscattering. As shown in previous studies the backscattering can explain unusual conduction properties, observed in these alloys, such as for example the increase of conductivity with disorder.

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“…[12][13][14] These anomalous transport properties of QC's are believed to arise from peculiar spectral features around the Fermi energy, F . A wide pseudogap ͑ϳ1 eV͒ was expected [15][16][17][18] ͑as a consequence of Hume-Rothery stabilization and hybridization͒ and confirmed experimentally. [19][20][21][22][23] Moreover, numerical calculations 15,17,24,25 for realistic approximant models of QC's reveal a spiky spectral structure throughout the valence band as a result of almost dispersionless bands.…”

Section: Introductionmentioning

confidence: 79%

Analytical expressions for the transport coefficients of icosahedral quasicrystals

2003

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We investigate by analytical means the electronic transport properties of approximants and quasicrystals. The spectral resistivity is modeled by Lorentz functions in agreement with realistic ab initio calculations ͑linear muffin-tin orbital basis, Kubo-Greenwood formula͒ for low-order approximants. The analytical expressions for the transport coefficients compare well with both numerical calculations and experiments. Thus, the temperature-dependent conductivity, thermopower, electronic thermal conductivity, and Lorenz number of certain approximants and quasicrystals can be consistently explained.

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Electronic structure in the Al-Mn alloy crystalline analog of quasicrystals

Abstract: Electronic structure in crystalline a-(Al»4Mn24) is calculated by the linear muffin-tin orbitalatomic-sphere approximation method with the local-density-functional theory. The density

Cited by 224 publications

References 15 publications

Quantum Transport of Slow Charge Carriers in Quasicrystals and Correlated Systems

Quantum Transport of Slow Charge Carriers in Quasicrystals and Correlated Systems

Ab-Initio Quantum Diffusion in Quasicrystals

Analytical expressions for the transport coefficients of icosahedral quasicrystals

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