Magnetic excitations and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>c</mml:mi></mml:math>-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>f</mml:mi></mml:math>hybridization effect in PrTi<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>Al<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>20</mml:mn

Tokunaga, Y.; Sakai, Hironori; Kambe, S.; Sakai, Akito; Nakatsuji, Satoru; Harima, Hisatomo

doi:10.1103/physrevb.88.085124

Cited by 40 publications

(28 citation statements)

References 29 publications

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“…[21][22][23][24][25][26] Various measurements indicate that the Al-based materials are characterized by stronger hybridization between conduction and f electrons than the Zn-based materials, leading to anomalous transport properties and their pronounced pressure depen- * E-mail : taka.taniguchi@issp.u-tokyo.ac.jp dence. 4,[23][24][25][26][27][28][29][30] In this paper, we focus on PrTi 2 Al 20 . The magnetic susceptibility for H 111 is nearly independent of temperature below 20 K, indicating van Vleck paramagnetism with a nonmagnetic CEF ground state.…”

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NMR Observation of Ferro-Quadrupole Order in PrTi₂Al₂₀

et al. 2016

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We report the results of 27 Al-NMR measurements on a single crystal of PrTi 2 Al 20 . This compound shows a phase transition near 2 K associated with the quadrupole degree of freedom of Pr ions, for which the ground state of the crystalline electric field is a nonmagnetic doublet. When a magnetic field is applied along the 111 direction, the NMR lines split upon entering the low-temperature phase, indicating the breaking of the three fold rotation symmetry due to the field-induced magnetic dipole perpendicular to the field. This provides microscopic evidence for a ferro order of the O 20 quadrupole. Although a first-order transition is expected theoretically, the line splitting evolves continuously within the experimental resolution.KEYWORDS: PrTi 2 Al 20 , NMR, quadrupole order, symmetry breaking Multipoles of f electrons in rare-earth compounds show a wide variety of phenomena. [1][2][3][4] In particular, non-Kramers rare-earth ions with an even number of f electrons in a cubic environment have been attracting strong interest recently. [5][6][7][8][9][10][11] In these systems, it is possible that the ground states of the J multiplet split by the cubic crystalline electric field (CEF) are nonmagnetic, i.e., the matrix elements of the magnetic dipole J are identically zero, yet have a degeneracy that allows active higher-order multipoles such as electric quadrupoles or magnetic octupoles. Then various interesting phenomena such as multipole orders [12][13][14] or multichannel Kondo effects 15,16) are expected at low temperatures.These possibilities have indeed been realized in compounds containing Pr 3+ ions with the 4 f 2 electronic configuration. The nine states of the J = 4 ground multiplet are split by a cubic CEF into the Γ 1 nonmagnetic singlet, the Γ 3 nonmagnetic doublet, the Γ 4 magnetic triplet, and the Γ 5 magnetic triplet. If the CEF ground state is the Γ 3 doublet, we encounter an interesting situation that the ground state is nonmagnetic but has nonzero matrix elements for the two types of quadrupoles, O 20 = (3J 2 z −J 2 )/2 and O 22 = √ 3(J 2 x −J 2 y )/2, and one octupole T xyz = ( √ 15/6)J x J y J z , where the bar represents the sum over the possible permutations of the indices x, y, and z. 13) The series of compounds PrT 2 X 20 (T : transition metal, X: Zn or Al) provides particularly interesting examples of the Γ 3 CEF ground states. 4) As shown in Fig. 1 [18][19][20][21] all of which also show superconductivity. [21][22][23][24][25][26] Various measurements indicate that the Al-based materials are characterized by stronger hybridization between conduction and f electrons than the Zn-based materials, leading to anomalous transport properties and their pronounced pressure depen- * E-mail : taka.taniguchi@issp.u-tokyo.ac.jp dence. 4,[23][24][25][26][27][28][29][30] In this paper, we focus on PrTi 2 Al 20 . The magnetic susceptibility for H 111 is nearly independent of temperature below 20 K, indicating van Vleck paramagnetism with a nonmagnetic CEF ground state. 29) Specific heat measurements ...

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NMR Observation of Ferro-Quadrupole Order in PrTi₂Al₂₀

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“…These materials have the nonmagnetic Γ 3 CEF ground state with the well separated excited state at ∆ CEF ∼ 60 K (Ti) and 40 K (V), as confirmed by various experiments [13,15,16], and * Electronic address: satoru@issp.u-tokyo.ac.jp exhibit the respective ferro-and antiferro-quadrupole ordering at T Q = 2.0 K (Ti) and 0.6 K (V) [13,15,17]. Significantly, strong c-f hybridization is evident from a number of phenomena, including the Kondo effect in the resistivity, Kondo resonance peak observed near the Fermi energy, and the large hyperfine constant in NMR measurements [13,18,19]. In addition, the hybridiza- In this Letter, we report the first observation of heavy fermion SC in a cubic Γ 3 doublet compound under ambient pressure.…”

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Heavy-Fermion Superconductivity in the Quadrupole Ordered State ofPrV2Al20

et al. 2014

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PrV2Al20 is a rare example of a heavy fermion system based on strong hybridization between conduction electrons and nonmagnetic quadrupolar moments of the cubic Γ3 ground doublet. Here, we report that a high-quality single crystal of PrV2Al20 exhibits superconductivity at Tc = 50 mK in the antiferroquadrupole-ordered state under ambient pressure. The heavy fermion character of the superconductivity is evident from the specific heat jump of ∆C/T ∼ 0.3 J/mol K 2 and the effective mass m * /m0 ∼ 140 estimated from the temperature dependence of the upper critical field. Furthermore, the high-quality single crystals exhibit double transitions at TQ = 0.75 K and T * = 0.65 K associated with quadrupole and octapole degrees of freedom of the Γ3 doublet. In the ordered state, the specific heat C/T shows a T 3 dependence, indicating the gapless mode associated with the quadrupole and/or octapole order. The strong sensitivity to impurity of the superconductivity suggests unconventional character due to significant quadrupolar fluctuations.PACS numbers: 74.70. Tx, 75.25.Dk, 72.15.Qm 4f electron systems exhibit a large variety of nontrivial ground states by tuning the hybridization between localized 4f and conduction (c−) electrons. Especially, emergence of exotic superconductivity (SC) with a large effective mass from unconventional quantum criticality has attracted much attention [1][2][3][4][5]. While most of the examples have been reported at the border of magnetism [6,7], similarly exotic states of matter may be found in the vicinity of quantum phase transition associated with different degrees of freedom of f -electrons, such as electrical quadrupole (orbital) and valence. In particular, experimental exploration of the quadrupolar instability is important since few studies on the associated quantum criticality has been made to date.For the exploration, the simplest example could be found in materials that carry no magnetic but quadrupole moments. Such a nonmagnetic ground state is known as the Γ 3 doublet in the cubic crystalline electric field (CEF) of a f 2 configuration. Intensive studies have revealed various interesting states in the cubic Γ 3 doublet systems, in particular in Pr-based intermetallic compounds [8][9][10][11][12]. However, Pr-based cubic Γ 3 doublet systems usually have well-localized quadrupole moments, and thus until quite recently there have been no study on the quadrupolar instability by tuning the c-f hybridization.PrT r 2 Al 20 (T r = Ti, V) has been reported as a rare example of cubic Γ 3 -doublet based Kondo lattice systems where one may tune the hybridization strength between quadrupole moments and conduction electrons by chemical substitution and by pressure [13,14]. These materials have the nonmagnetic Γ 3 CEF ground state with the well separated excited state at ∆ CEF ∼ 60 K (Ti) and 40 K (V), as confirmed by various experiments [13,15,16], and * Electronic address: satoru@issp.u-tokyo.ac.jp exhibit the respective ferro-and antiferro-quadrupole ordering at T Q = 2.0 K (Ti) and 0.6 K (...

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“…Then, the principal axis directions are ⟨100⟩, ⟨011⟩, and ⟨011⟩. From the previous studies of PrT2Al20 (T = Ti, V, and Nb) [10][11][12], VXX and VZZ are determined to be parallel with ⟨100⟩ and ⟨011⟩, respectively. In such a case, the transformation is given by RCQ(1)(0°, −45°, 0°) for the site at (x, 1/8, 1/8) with x ≃ 0.48.…”

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²⁷Al-NMR/NQR Spectral Analysis of Single Crystal PrTa₂Al₂₀

Kubo

Tou

Miyake

et al. 2020

Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2019)

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We report the results and analysis of 27 Al nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements. NMR measurements were performed at the magnetic field parallel to ⟨111⟩ between 5 and 12 T. NQR measurements were performed at 4.2 K. Although the signals from the Al 16c site could not be deconvoluted, the 27 Al-NMR signals are assigned and electric field gradient (EFG) parameters are extracted for both the Al 48f and 96g sites. The obtained NQR parameters are νQ(48f) = 2.418±0.002 MHz, η(48f) = 0.175±0.005, νQ(96g) = 1.00±0.01 MHz, and η(96g) = 0.40±0.05. The EFG directions at the Al 48f site are determined to be VZZ ∥ ⟨110⟩ and VXX ∥ ⟨100⟩. For the Al 96g site, VZZ ∥ ⟨110⟩ and VXX tilts by 14°±3° from ⟨110⟩ to ⟨001⟩.

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Magnetic excitations andc-fhybridization effect in PrTi2Al20

Cited by 40 publications

References 29 publications

NMR Observation of Ferro-Quadrupole Order in PrTi₂Al₂₀

NMR Observation of Ferro-Quadrupole Order in PrTi₂Al₂₀

Heavy-Fermion Superconductivity in the Quadrupole Ordered State ofPrV2Al20

²⁷Al-NMR/NQR Spectral Analysis of Single Crystal PrTa₂Al₂₀

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Magnetic excitations andc-fhybridization effect in PrTi2Al20

Cited by 40 publications

References 29 publications

NMR Observation of Ferro-Quadrupole Order in PrTi2Al20

NMR Observation of Ferro-Quadrupole Order in PrTi2Al20

Heavy-Fermion Superconductivity in the Quadrupole Ordered State ofPrV2Al20

27Al-NMR/NQR Spectral Analysis of Single Crystal PrTa2Al20

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Product

Resources

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NMR Observation of Ferro-Quadrupole Order in PrTi₂Al₂₀

NMR Observation of Ferro-Quadrupole Order in PrTi₂Al₂₀

²⁷Al-NMR/NQR Spectral Analysis of Single Crystal PrTa₂Al₂₀