Effect of pressure on the intermediate-valence semiconductor SmB6: 11B-NMR

Nishiyama, K.; Mito, T.; Ueda, Ken–ichi; Koyama, T.; Kohara, T.; Pristáš, G.; Gabáni, S.; Reiffers, M.; Flachbart, К.; Komaki, Yasuhiro; Kokubu, Mitsutane; Fukazawa, Hideto; Kohori, Yoh; Takeshita, Nao; Shitsevalova, N.

doi:10.3938/jkps.62.2024

Cited by 4 publications

(3 citation statements)

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“…8,9) NMR measurement is a powerful tool for probing electronic states through not only local magnetic interactions but also local electric interactions. Recent technical development enables one to perform NMR measurements at very high pressures exceeding 5 GPa.…”

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confidence: 99%

Pressure-Induced Localization of 4f Electrons in the Intermediate Valence Compound SmB₆

et al. 2013

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We report high-pressure studies of X-ray diffraction and 11 B-nuclear magnetic resonance (NMR) in the intermediatevalence compound SmB 6 . The pressure dependence of the lattice constant was precisely determined and no anomaly was observed up to 9.1 GPa. The temperature dependence of the nuclear quadrupole resonance frequency Q , obtained from the 11 B-NMR measurements, is predominantly contributed by on-site charge distribution. Using the relationship between Q and Sm valence at ambient pressure reported previously, we estimate the pressure dependence of the Sm valence up to 6 GPa as well. The increase in the Sm valence accelerates with pressure and reaches an increase of about 10% at 6 GPa. The pressure-induced localization of Sm 4f -holes may be responsible for the long-range magnetic order under pressure.SmB 6 with a cubic CaB 6 -type structure has been intensively studied since the 1960s because of its notable features, for example, an intermediate valence state [Sm valence is $2:6 (see Refs. 1 and 2 and references therein)] and a semiconducting property with a narrow gap (50-100 K 3,4) ). Gap formation in the so-called ''Kondo insulator'' is thought to arise from the hybridization of narrow f bands with a broad conduction band. The insulating gap of SmB 6 is known to be suppressed by the application of pressure, and subsequently, SmB 6 becomes metallic above pressures in the range of 4-7 GPa. 5) Recently, a new magnetically ordered phase has been found above $6 GPa in SmB 6 by highpressure 149 Sm nuclear forward-scattering measurement, so that interest in this compound has been renewed. 6) The physical properties of SmB 6 involve many key factors common to strongly correlated electron systems, such as valence, insulating gap, magnetism, and the Kondo effect.The long-range magnetic order in SmB 6 is expected to result from the localization of Sm 4f electrons on the basis of the general phase diagram of heavy-fermion compounds, that is, the magnetic trivalent state of Sm ions (total angular momentum J ¼ 5=2) becomes more stable than the divalent state (J ¼ 0) under pressure, analogous to the case of Ybbased compounds. The high-pressure properties of this compound have thus far been studied mainly in terms of the P-dependence of the insulating gap by transport measurements. 5,7) However, the microscopic understanding of the P-T phase diagram has been incomplete owing to insufficient experimental information on how the electronic configuration (or valence) varies as pressure increases toward the critical pressure P c of a nonmagnetic-magnetic transition.To address this problem, we carried out nuclear magnetic resonance (NMR) measurements at the B-site under pressure. 8,9) NMR measurement is a powerful tool for probing electronic states through not only local magnetic interactions but also local electric interactions. Recent technical development enables one to perform NMR measurements at very high pressures exceeding 5 GPa. In this letter, we present our latest study of nuclear quadrupole interactions up to 6 G...

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Pressure-Induced Localization of 4f Electrons in the Intermediate Valence Compound SmB₆

et al. 2013

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“…Nuclear magnetic resonance measurements on floating-zone SmB 6 have been performed under hydrostatic pressures to 5 GPa [173][174][175]. The temperature dependence of the spin lattice relaxation remains activated under pressure, though the insulating gap is reduced by about 30% at 5 GPa.…”

Section: Nuclear Electron and Muon Spin Resonancementioning

confidence: 99%

Bulk and surface properties of SmB6

Rosa¹,

Fisk²

2020

Preprint

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Samarium hexaboride crystallizes in a simple cubic structure (space group #221, Pm3m), but its properties are far from being straightforward. Initially classified as a Kondo insulator born out of its intriguing intermediate valence ground state, SmB 6 has been recently predicted to be a strongly correlated topological insulator. The subsequent experimental discovery of surface states has revived the interest in SmB 6 , and our purpose here is to review the extensive and in many aspects perplexing experimental record of this material. We will discuss both surface and bulk properties of SmB 6 with an emphasis on the role of crystal growth and sample preparation. We will also highlight the remaining mysteries and open questions in the field.Rare-Earth Borides Dmytro S. Inosov (ed.

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“…Recent investigations propose that the surface Kondo breakdown is responsible for the metallic surface state [72,73], which may be associated to these two puzzling behaviors. Many high-pressure studies on SmB 6 have been carried out [41,42,[74][75][76][77][78][79] before the prediction that SmB 6 is a candidate of topological Kondo insulator. Several high-pressure electrical resistivity measurements found the same phenomena of an existing resistance plateau at temperature below 3-5 K, a narrow-gap in the temperature range below 15 K and a hybridization gap at temperature below 100 K at pressure below 4 GPa [74][75][76][77].…”

Section: Pressure-induced Exotic Insulator-metal Transition In Smbmentioning

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Pressure-induced exotic states in rare earth hexaborides

Sun¹,

2016

Rep. Prog. Phys.

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Finding the exotic phenomena in strongly correlated electron systems (SCESs) and understanding the corresponding microphysics have long been the research frontiers of condensed matter physics. The remarkable examples for the intriguing phenomena discovered in past years include unconventional superconductivity, heavy Fermion behaviors, giant magneto-resistance and so on. A fascinating type of rare earth hexaboride RB6 (R = Sm, Yb, Eu and Ce) belongs to a strongly correlated electron system (SCES), but shows unusual ambient-pressure and high-pressure behaviors beyond the phenomena mentioned above. Particularly, the recent discovery of the coexistence of an unusual metallic surface state and an insulating bulk state in SmB6, known to be a Kondo insulator decades ago, by theoretical calculations and many experimental measurements creates new interest for the investigation of the RB6. This significant progress encourages people to revisit the RB6 with an attempt to establish a new physics that links the SCES and the unusual metallic surface state which is a common feature of a topological insulator (TI). It is well known that pressure has the capability of tuning the electronic structure and modifying the ground state of solids, or even inducing a quantum phase transition which is one of the kernel issues in studies of SCESs. In this brief review, we will describe the progress in high pressure studies on the RB6 based on our knowledge and research interests, mainly focusing on the pressure-induced phenomena in YbB6 and SmB6, especially on the quantum phase transitions and their connections with the valence state of the rare earth ions. Moreover, some related high-pressure results obtained from CeB6 and EuB6 are also included. Finally, a summary is given in the conclusions and perspectives section.

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Effect of pressure on the intermediate-valence semiconductor SmB6: 11B-NMR

Cited by 4 publications

References 14 publications

Pressure-Induced Localization of 4f Electrons in the Intermediate Valence Compound SmB₆

Pressure-Induced Localization of 4f Electrons in the Intermediate Valence Compound SmB₆

Bulk and surface properties of SmB6

Pressure-induced exotic states in rare earth hexaborides

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Effect of pressure on the intermediate-valence semiconductor SmB6: 11B-NMR

Cited by 4 publications

References 14 publications

Pressure-Induced Localization of 4f Electrons in the Intermediate Valence Compound SmB6

Pressure-Induced Localization of 4f Electrons in the Intermediate Valence Compound SmB6

Bulk and surface properties of SmB6

Pressure-induced exotic states in rare earth hexaborides

Contact Info

Product

Resources

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Pressure-Induced Localization of 4f Electrons in the Intermediate Valence Compound SmB₆

Pressure-Induced Localization of 4f Electrons in the Intermediate Valence Compound SmB₆