Metallic islands in the Kondo insulator 
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Souza, J. C.; Rosa, Priscila; Sichelschmidt, J.; Carlone, M.; Venegas, P. A.; Malcolms, M. O.; Menegasso, Paulo; Urbano, R. R.; Fisk, Z.; Pagliuso, P. G.

doi:10.1103/physrevresearch.2.043181

Cited by 14 publications

(24 citation statements)

References 71 publications

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“…4(a)), we obtain E ex = 60 K, which is close to the SmB 6 hybridization gap [7]. We used ∆H res ≈ 20 Oe, and as expected, there is no Korringa relaxation rate at low-T , but a small one, b = 0.01(2) Oe/K, is observed for T above 8 K, consistent with the bulk conductivity [7,30] that sets in near this temperature.…”

Section: Resultssupporting

confidence: 80%

“…This small misalignment would allow to perceive any linewidth anomaly caused by an even tiny CEF effect. The linewidth broadens caused by the slow dynamic CEF fluctuation and the lineshape goes from pure Lorentzian to Dysonian one, due to the decrease of the skin depth as a consequence of the conductivity increase in this anomalous linewidth temperature interval [30]. Figure 4(a) shows the T -dependence of the X and Qband Gd 3+ ESR linewidth near the collapsed angle for Sm 0.9996 Gd 0.0004 B 6 .…”

Section: Resultsmentioning

confidence: 99%

“…The studied sample masses ranged from 0.3 mg to 4.0 mg. Along this report, the concentration x refers to the nominal concentration value [30].…”

Section: Methodsmentioning

confidence: 99%

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Slow crystalline electric field fluctuations in the Kondo lattice SmB$_{6}$

Carlone,

Souza,

Sichelschmidt

et al. 2022

Preprint

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This work reports on the temperature dependence of the electron spin resonance (ESR) of Gd 3+doped SmB6 single crystals at X-and Q-band microwave frequencies in different crystallographic directions. We found an anomalous inhomogeneous broadening of the Gd 3+ ESR linewidth (∆H) within 5.3 K ≤ T ≤ 12.0 K which is attributed to slow crystalline electric field (CEF) fluctuations, slower than the timescale of the ESR microwave frequencies used (∼10 GHz). This linewidth inhomogeneity may be associated to the coupling of the Gd 3+ S-states to the breathing mode of the SmB6 cage, and can be simulated by a random distribution of the 4 th CEF parameter, b4, that strikingly takes negative and positive values. The temperature at which this inhomogeneity sets in, is related to the onset of a continuous insulator-to-metal phase transition. In addition, based on the interconfigurational fluctuation relaxation model, the observed exponential T -dependence of ∆H above T 10 K gives rise to an excitation energy notably close to the hybridization gap of SmB6 (∆ 60 K). This charge fluctuation scenario provides important ingredients to the physical properties of SmB6. We finally discuss the interplay between charge and valence fluctuations under the view of slow CEF fluctuations in SmB6 by coupling the Gd 3+ ions to the breathing phonon mode via a dynamic Jahn-Teller-like mechanism.

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Section: Resultssupporting

confidence: 80%

Section: Resultsmentioning

confidence: 99%

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Slow crystalline electric field fluctuations in the Kondo lattice SmB$_{6}$

Carlone,

Souza,

Sichelschmidt

et al. 2022

Preprint

Self Cite

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“…These findings set the stage for a holistic understanding of the interplay between strong correlations and topological features in the electron system. Moreover, they validate recent analyses suggesting that the electronic structure of SmB6 can present the key hallmarks of conventional electron doping, such as a Fermi surface, while nonetheless preserving longrange insulating character in electrical transport measurements [8][9][10] .…”

Section: Controlling the Density Of Electrons Inside An Insulator Via...supporting

confidence: 82%

Metallic chemical potentials in an insulating topological state

Kotta

Lee

et al. 2022

Preprint

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Controlling the density of electrons inside an insulator via the chemical potential is a cornerstone of modern electronics, enabling the electrical conductivity of semiconductors and the emergence of fascinating new properties linked with electronic correlations. The compound SmB6 has drawn widespread attention in recent years as the first insulator to feature both strong electronic correlations and topological quantum order1-7, potentially enabling a host of new phenomenologies as charge density is modified. However, chemical potential has not been experimentally controlled in studies to date of the electronic structure. Here we present an angle-resolved photoemission spectromicroscopy (μ-ARPES) study of SmB6 alloys, using the natural inhomogeneity of sample surfaces to create the analogue of a multi-dimensional doping series. The role of electronic correlations is observed in the interplay of the topologically ordered conducting states with one another and with the chemical potential. Higher doping is found to result in the transformation of these interdependencies as the disorder from impurities erodes quantum coherence. These findings set the stage for a holistic understanding of the interplay between strong correlations and topological features in the electron system. Moreover, they validate recent analyses suggesting that the electronic structure of SmB6 can present the key hallmarks of conventional electron doping, such as a Fermi surface, while nonetheless preserving long-range insulating character in electrical transport measurements8-10.

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“…Debate is ongoing about the role of Gd impurities; recent reports have suggested that Gd impurities are not responsible for bulk dHvA oscillations [67]. However, the local environment of Gd impurities is metallic even at very low concentrations, and at higher concentrations this local environment could lead to percolation through the sample in transport measurements [68].…”

Section: Resultsmentioning

confidence: 99%

Bulk transport paths through defects in floating zone and Al flux grown SmB6

Rakoski

Sinha

et al. 2021

Phys. Rev. Materials

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We investigate the roles of disorder on low-temperature transport in SmB 6 crystals grown by both the Al flux and floating zone methods. We used the inverted resistance method with Corbino geometry to investigate whether low-temperature variations in the standard resistance plateau arise from a surface or a bulk channel in floating zone samples. The results show significant sample-dependent residual bulk conduction, in contrast to smaller amounts of residual bulk conduction previously observed in Al flux grown samples with Sm vacancies. We consider hopping in an activated impurity band as a possible source for the observed bulk conduction, but it is unlikely that the large residual bulk conduction seen in floating zone samples is solely due to Sm vacancies. We therefore propose that one-dimensional defects, or dislocations, contribute as well. Using chemical etching, we find evidence for dislocations in both flux and floating zone samples, with higher dislocation density in floating zone samples than in Al flux grown samples. In addition to the possibility of transport through one-dimensional dislocations, we also discuss our results in the context of recent theoretical models of SmB 6 .

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Metallic islands in the Kondo insulator SmB6

Cited by 14 publications

References 71 publications

Slow crystalline electric field fluctuations in the Kondo lattice SmB$_{6}$

Slow crystalline electric field fluctuations in the Kondo lattice SmB$_{6}$

Metallic chemical potentials in an insulating topological state

Bulk transport paths through defects in floating zone and Al flux grown SmB6

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