Intermediate-valence icosahedral Au-Al-Yb quasicrystal

Watanuki, Tetsu; Kashimoto, Shiro; Kawana, Daichi; Yamazaki, T.; Machida, Akihiko; Tanaka, Yuya; Sato, Taku

doi:10.1103/physrevb.86.094201

Cited by 75 publications

(66 citation statements)

References 23 publications

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“…With respect to this fact, there are two possible interpretations. One is dynamic movement of the tetrahedron recently observed in Zn 6 Sc approximant [6], and the other is static and disordered arrangement of tetrahedron [5] and approximant [16,17].…”

Section: Methodsmentioning

confidence: 99%

Tsai-Type Quasicrystal and Its Approximant in Au-Al-Tm Alloys

Tanaka

Ishimasa

et al. 2014

Acta Phys. Pol. A

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A P-type icosahedral quasicrystal with a six-dimensional lattice parameter a6D = 7.411 Å is formed as an equilibrium phase in AuAlTm alloy, of which composition was analyzed to be Au46Al38Tm16 by electron probe microanalysis. This quasicrystal is observed as a predominant phase in both as-cast and Au49Al34Tm17 alloys annealed at 910• C, and as one of main phases in the alloy slowly cooled from 1020A 1/1 approximant, Au48Al38Tm14, is also formed near the composition of the quasicrystal. This is a body-centered cubic structure (space group: Im3) with a lattice parameter a = 14.458 Å that is an isostructure to the recently reported 1/1Tsai-type approximant in AuAlYb. This approximant is characterized by disorderly arranged four AuAl atoms centered at the Tsai-type cluster, presence of atoms at 8c site, and chemical ordering of Au and Al at sites forming a partial triacontahedron.

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Section: Methodsmentioning

confidence: 99%

Tsai-Type Quasicrystal and Its Approximant in Au-Al-Tm Alloys

Tanaka

Ishimasa

et al. 2014

Acta Phys. Pol. A

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“…1,2) The measured criticality such as magnetic susceptibility χ ∼ T −0.5 , NMR relaxation rate (T 1 T ) −1 ∼ T −0.5 , specific heat C e /T ∼ − log T , and resistivity ρ ∼ T is unconventional and quite similar to those observed in periodic crystals such as heavy-electron metals YbRh 2 Si 2 3) and β-YbAlB 4 , 4,5) which are well explained by quantum critical phenomena of Yb-valence fluctuations.…”

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confidence: 99%

Origin of Quantum Criticality in Yb–Al–Au Approximant Crystal and Quasicrystal

Watanabe

Miyake

2016

J. Phys. Soc. Jpn.

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To get insight into the mechanism of emergence of unconventional quantum criticality observed in quasicrystal Yb 15 Al 34 Au 51 , the approximant crystal Yb 14 Al 35 Au 51 is analyzed theoretically. By constructing a minimal model for the approximant crystal, the heavy quasiparticle band is shown to emerge near the Fermi level because of strong correlation of 4f electrons at Yb. We find that charge-transfer mode between 4f electron at Yb on the 3rd shell and 3p electron at Al on the 4th shell in Tsai-type cluster is considerably enhanced with almost flat momentum dependence.The mode-coupling theory shows that magnetic as well as valence susceptibility exhibits χ ∼ T −0.5 for zero-field limit and is expressed as a single scaling function of the ratio of temperature to magnetic field T/B over four decades even in the approximant crystal when some condition is satisfied by varying parameters, e.g., by applying pressure. The key origin is clarified to be due to the strong locality of the critical Yb-valence fluctuation and small Brillouin zone reflecting the large unit cell, giving rise to the extremely-small characteristic energy scale. This also gives a natural explanation for the quantum criticality in the quasicrystal corresponding to the infinite limit of the unit-cell size.Recent discovery of unconventional quantum critical phenomena in quasicrystal Yb 15 Al 34 Au 51 has attracted much attention.1, 2) The measured criticality such as magnetic susceptibility χ ∼ T −0.5 , NMR relaxation rate (T 1 T ) −1 ∼ T −0.5 , specific heat C e /T ∼ − log T , and resistivity ρ ∼ T is unconventional and quite similar to those observed in periodic crystals such as heavy-electron metals YbRh 2 Si 2 3) and β-YbAlB 4 , 4,5) which are well explained by quantum critical phenomena of Yb-valence fluctuations.6)The quasicrystal Yb 15 Al 34 Au 51 is constituted of concentric shell structures of Tsai-type cluster shown in Fig. 1. 1, 7) There also exists approximant crystal Yb 14 Al 35 Au 51 .7) The approximant crystal has periodic arrangement of the body-centered cubic (bcc) structure whose unit cell contains shell structures shown in Figs. 1(a)-1(e). Theoretical analysis of the Yb-AlAu cluster taking account of critical Yb-valence fluctuations has provided a natural explanation for robustness of quantum criticality in the quasicrystal measured under pressure and has pointed out a possibility that the same criticality appears even in the approximant crystal when pressure is applied. 8,9) On the other hand, a new theoretical framework for critical Yb-valence fluctuation under magnetic field has been developed recently.10) The theory has succeeded in explaining novel scaling discovered in β-YbAlB 4 where the magnetic susceptibility χ is expressed as a single scaling function of the ratio of temperature to magnetic field T/B over four decades. 5)Surprisingly, recent measurement of magnetic susceptibility in the quasicrystal Yb 15 Al 34 Au 51 has revealed that the same T/B-scaling behavior appears over six decades of T/B.11) This strongly s...

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“…Furthermore, we have found that the quasiparticle weight strongly depends on the site and its geometry. It is also interesting to study the periodic Anderson model on the quasiperiodic lattice since the valence of the ytterbium ions in the compound Au 51 Al 34 Yb 15 is intermediate, 21) which is now under consideration. The authors would like to thank R. Peters, T. Pruschke, and S. Wessel for valuable discussions.…”

Section: )mentioning

confidence: 99%

Local Electron Correlations in a Two-Dimensional Hubbard Model on the Penrose Lattice

Takemori

Koga

2015

J. Phys. Soc. Jpn.

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We study electron correlations in the half-filled Hubbard model on two-dimensional Penrose lattice. Applying the real-space dynamical mean-field theory to large clusters, we discuss how low-temperature properties are affected by the quasiperiodic structure. By calculating the double occupancy and renormalization factor at each site, we clarify the existence of the Mott transition. The spatially-dependent renormalization characteristic of geometrical structure is also addressed. KEYWORDS: Hubbard model, Penrose lattice, dynamical mean-field theoryQuasiperiodic systems have attracted considerable interest since the discovery of quasicrystal.1) One of the specific features is the existence of the long-range order without translational symmetry. This should induce interesting low-temperature properties in the metallic quasicrystals such as electric and thermal conductivities.2, 3) The tight-binding model on the quasiperiodic lattices, which may describe some quasicrystal compounds, has been studied and intrinsic properties such as the existence of the confined state and fractal dimensions, have been clarified. 7,8) In the former compound, the specific heat and susceptibility exhibit power-law behavior with a nontrivial exponent at low temperatures. In contrast, the approximant with the periodic structure shows conventional heavy fermion behavior. These should suggest that electron correlations and quasiperiodic structure play a crucial role in stabilizing quantum critical behavior at low temperatures. Therefore, it is desirable to clarify how electron correlations affect low temperature properties in the quasiperiodic system.Motivated by this, we study correlated electron systems on the quasiperiodic lattice. One of the simplest questions is how the introduction of the Coulomb interaction forms the quasiparticles and leads to the Mott transition in the system since coordination number and geometrical structure depend on the lattice sites. To attack this fundamental problem, we focus on the halffilled Hubbard model on a two-dimensional Penrose lattice, where a site is placed on each vertex of the rhombuses [see Fig. 1(a)]. We apply the real-space dynamical mean-field theory (RDMFT) 9) to the Hubbard model, and discuss electron correlations in the system. Calculating renormalization factor and double occupancy at each site, we study how the Coulomb interactions yield the spatially-dependent renormalization, typically close to the Mott transition point.In this paper, we consider the single-band Hubbard model on the Penrose lattice, which should be given by * E-mail address: takemori@stat.phys.titech.ac.jp

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Intermediate-valence icosahedral Au-Al-Yb quasicrystal

Cited by 75 publications

References 23 publications

Tsai-Type Quasicrystal and Its Approximant in Au-Al-Tm Alloys

Tsai-Type Quasicrystal and Its Approximant in Au-Al-Tm Alloys

Origin of Quantum Criticality in Yb–Al–Au Approximant Crystal and Quasicrystal

Local Electron Correlations in a Two-Dimensional Hubbard Model on the Penrose Lattice

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