High-field suppression of in-gap states in the Kondo insulator<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">Sm</mml:mi><mml:msub><mml:mi mathvariant="normal">B</mml:mi><mml:mn>6</mml:mn></mml:msub></mml:mrow></mml:math>

Caldwell, T.; Reyes, A. P.; Moulton, W. G.; Kuhns, P. L.; Hoch, M.; Schlottmann, P.; Fisk, Z.

doi:10.1103/physrevb.75.075106

Cited by 70 publications

(73 citation statements)

References 35 publications

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“…(v) There seems to be an additional, broadened hump close to −3 meV, i.e., inside the hybridization gap. One may speculate that this feature is related to in-gap states seen in other measurements (19)(20)(21)(45)(46)(47). Specifically, it is observed only for T ≤ 12 K (Fig.…”

Section: Resultsmentioning

confidence: 76%

Hybridization gap and Fano resonance in SmB₆

Rößler¹,

Jang

Kim

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

124

160

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Hybridization between conduction electrons and the strongly interacting f-electrons in rare earth or actinide compounds may result in new states of matter. Depending on the exact location of the concomitant hybridization gap with respect to the Fermi energy, a heavy fermion or an insulating ground state ensues. To study this entanglement locally, we conducted scanning tunneling microscopy and spectroscopy (STS) measurements on the "Kondo insulator" SmB 6 . The vast majority of surface areas investigated were reconstructed, but infrequently, patches of varying sizes of nonreconstructed Smor B-terminated surfaces also were found. On the smallest patches, clear indications for the hybridization gap with logarithmic temperature dependence (as expected for a Kondo system) and for intermultiplet transitions were observed. On nonreconstructed surface areas large enough for coherent cotunneling, we were able to observe clear-cut Fano resonances. Our locally resolved STS indicated considerable finite conductance on all surfaces independent of their structure, not proving but leaving open the possibility of the existence of a topologically protected surface state.M aterials with strong electron correlations continue to draw enormous attention, not only because they may give rise to fundamentally new states of matter or new phenomena but also because of the hope for advanced technological applications. Heavy fermion (HF) materials, i.e., intermetallics of certain rare earths (REs), such as Ce, Sm, and Yb, are model systems to study strong electronic correlations (1). Here, the RE-derived localized 4f states are covalently mixed with the conduction-band states and, thus, acquire a finite lifetime. The associated decay rate in relation to the energy of the localized 4f state corresponds to the valency. In an Sm-based HF system, the valence lies between 3+ (4f 5 ) and 2+ (4f 6 ), which implies a considerable amount of charge fluctuations. This usually is referred to as intermediate valence (2). In addition to the abovementioned mixing of 4f states and the conduction band, which is well described within the framework of one-electron models, a manybody interaction is operating between the 4f and conduction electrons. This "Kondo effect" (3) eventually leads to a screening of the local moments as a result of particle-hole excitations that are manifested by a narrow Abrikosov-Suhl, or Kondo, resonance at E F , the width of which is given by the single-ion Kondo temperature T K .Because of the periodic arrangement of REs in an HF intermetallic, the Kondo resonances form a weakly dispersive HF or "coherent 4f−" band, resulting in a heavy Fermi liquid state well below T K . The band interaction between the renormalized 4f and the conduction band generates a so-called hybridization gap, which opens at around T K . Under certain conditions, E F may reside inside this gap, characterizing a so-called Kondo insulator (4).SmB 6 is such a Kondo insulator, with a valence ν ∼ 2:6 (5), ν being slightly temperature dependent (6, 7). A sharp de...

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Section: Resultsmentioning

confidence: 76%

Hybridization gap and Fano resonance in SmB₆

Rößler¹,

Jang

Kim

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

124

160

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“…16 The "in-gap" states are very sensitive to an external magnetic field. 15 Remarkable is also the saturation of the resistivity below 4K as the temperature is reduced, indicating that at very low T SmB 6 is not compatible with the picture of a semiconductor/insulator. The "in-gap" states in the susceptibility emerge at a higher temperature (∼ 20 K) than the temperature at which the low T resistivity saturates.…”

Section: Introductionmentioning

confidence: 99%

“…[13][14][15] In earlier days the "in-gap" states have been attributed to magnetic excitations (exciton-like bound states) due to AF correlations. 16 The "in-gap" states are very sensitive to an external magnetic field.…”

Section: Introductionmentioning

confidence: 99%

NMR relaxation in the topological Kondo insulatorSmB6

Schlottmann¹

2014

Phys. Rev. B

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SmB6 has been predicted to be a strong topological Kondo insulator and experimentally it has been confirmed that at low temperatures the electrical conductivity only takes place at the surfaces of the crystal. We study the temperature and magnetic field dependence of the NMR Knight shift and relaxation rate arising from the topological conduction states. For the clean surface the Landau quantization of the surface states gives rise to highly degenerate discrete levels for which the Knight shift is proportional to the magnetic field B and inversely proportional to the temperature T . The relaxation rate, 1/T1, is not Korringa-like. For the more realistic case of a surface with a low concentration of defects (dirty limit) the scattering of the electrons leads to a broadening of the Landau levels and hence to a finite density of states. The mildly dirty surface case leads to a T -independent Knight shift proportional to B and a Korringa-like 1/T1 at low T . The wave functions of the surface states are expected to fall off exponentially with distance from the surface giving rise to a superposition of relaxation times, i.e. a stretched exponential. It is questionable that the experimental 11 B Knight shift and relaxation rate arise from the surface states of the TKI. An alternative explanation is that the bulk susceptibility and the 11 B NMR properties are the consequence of the in-gap bulk states originating from magnetic exciton bound states proposed by Riseborough [Phys. Rev. B 68, 235213 (2003)].

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“…25 It contains two rectangular bands of width W separated by a main gap of 2∆ with a narrow peak of in-gap states of width w with a density of states ρ i (ε) ∼ ρ 0 exp(−T /T 0 ) separated by the small gap of 2δ from the bottom of the conduction band (see Fig. 8, Top Inset).…”

Section: N -G a P S T A T E S C O N D U C T I Omentioning

confidence: 99%

Interplay between localized and itinerant magnetism in Co-substituted FeGa3

et al. 2014

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The evolution of the electronic structure and magnetic properties with Co substitution for Fe in the solid solution Fe1−xCoxGa3 was studied by means of electrical resistivity, magnetization, ab initio band structure calculations, and nuclear spin-lattice relaxation 1/T1 of the 69,71 Ga nuclei. Temperature dependencies of the electrical resistivity reveal that the evolution from the semiconducting to the metallic state in the Fe1−xCoxGa3 system occurs at 0.025 < x < 0.075. The 69,71 (1/T1) was studied as a function of temperature in a wide temperature range of 2−300 K for the concentrations x = 0.0, 0.5, and 1.0. In the parent semiconducting compound FeGa3, the temperature dependence of the 69 (1/T1) exhibits a huge maximum at about T ∼ 6 K indicating the existence of in-gap states. The opposite binary compound, CoGa3, demonstrates a metallic Korringa behavior with 1/T1 ∝ T . In Fe0.5Co0.5Ga3, the relaxation is strongly enhanced due to spin fluctuations and follows 1/T1 ∝ T 1/2 , which is a unique feature of weakly and nearly antiferromagnetic metals. This itinerant antiferromagnetic behavior contrasts with both magnetization measurements, showing localized magnetism with a relatively low effective moment of about 0.7 µB/f.u., and ab initio band structure calculations, where a ferromagnetic state with an ordered moment of 0.5 µB/f.u. is predicted. The results are discussed in terms of the interplay between the localized and itinerant magnetism including in-gap states and spin fluctuations.

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High-field suppression of in-gap states in the Kondo insulatorSmB6

Cited by 70 publications

References 35 publications

Hybridization gap and Fano resonance in SmB₆

Hybridization gap and Fano resonance in SmB₆

NMR relaxation in the topological Kondo insulatorSmB6

Interplay between localized and itinerant magnetism in Co-substituted FeGa3

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High-field suppression of in-gap states in the Kondo insulatorSmB6

Cited by 70 publications

References 35 publications

Hybridization gap and Fano resonance in SmB6

Hybridization gap and Fano resonance in SmB6

NMR relaxation in the topological Kondo insulatorSmB6

Interplay between localized and itinerant magnetism in Co-substituted FeGa3

Contact Info

Product

Resources

About

Hybridization gap and Fano resonance in SmB₆

Hybridization gap and Fano resonance in SmB₆