Specific heat of SmB6 at very low temperatures

Flachbart, К.; Gabáni, S.; Neumaier, K.; Paderno, Y.; Pavlı́k, V.; Schuberth, E.; Shitsevalova, N.

doi:10.1016/j.physb.2006.01.344

Cited by 25 publications

(33 citation statements)

References 7 publications

(9 reference statements)

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“…An estimate of the density of states can be obtained from the metallic contribution of the heat capacity, C ele = γT. Interestingly, heat capacity measurements find a surprisingly large metallic component at low temperatures, often on the order of 10 mJ K −2 mol −1 , in agreement with the observed large low energy spectral weight 23,45,46 . Additionally, recent measurements indicate that the large metallic heat capacity is independent of sample surface area and is therefore of bulk origin 44 .…”

Section: Coupling Of Bulk States To Spin Excitonsmentioning

confidence: 55%

“…However, these optical experiments on SmB 6 single crystals pre-date the TKI prediction and may require reinterpretation. Additionally, results from a number of heat capacity experiments reveal a very large low temperature fermionic heat capacity with a γ coefficient that is 2-25 mJ/mol ·K 2 (the same as some correlated metals) which has been shown to be of bulk origin 44 and therefore seemingly at odds with a bulk gapped state 23,45,46 .…”

Section: Introductionmentioning

confidence: 99%

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Anomalous three-dimensional bulk ac conduction within the Kondo gap of SmB6 single crystals

et al. 2016

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The Kondo insulator SmB6 has long been known to display anomalous transport behavior at low temperatures, T < 5 K. In this temperatures range, a plateau is observed in the dc resistivity, contrary to the exponential divergence expected for a gapped system. Recent theoretical calculations suggest that SmB6 may be the first topological Kondo insulator (TKI) and propose that the residual conductivity is due to topological surface states which reside within the Kondo gap. Since the TKI prediction many experiments have claimed to observe high mobility surface states within a perfectly insulating hybridization gap. Here, we investigate the low energy optical conductivity within the hybridization gap of single crystals of SmB6 via time domain terahertz spectroscopy. Samples grown by both optical floating zone and aluminum flux methods are investigated to probe for differences originating from sample growth techniques. We find that both samples display significant 3D bulk conduction originating within the Kondo gap. Although SmB6 may be a bulk dc insulator, it shows significant bulk ac conduction that is many orders of magnitude larger than any known impurity band conduction. The nature of these in-gap states and their coupling with the low energy spin excitons of SmB6 is discussed. Additionally, the well defined conduction path geometry of our optical experiments allows us to show that any surface states, which lie below our detection threshold if present, must have a sheet resistance of R/ ≥ 1000 Ω.

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Section: Coupling Of Bulk States To Spin Excitonsmentioning

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Anomalous three-dimensional bulk ac conduction within the Kondo gap of SmB6 single crystals

et al. 2016

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“…/dT (shown in Fig. 2d) remains finite in amplitude down to temperatures < 1 K, an order of magnitude below the charge gap 2-5 meV [8,13,21], providing evidence for a finite density of states within the charge gap. Importantly, we are able to Figure 2: Finite linear specific heat coefficient and quantum oscillatory entropy of SmB 6 .…”

mentioning

confidence: 88%

“…[17]) [13]. The nuclear contribution to the specific heat capacity is expected to be negligibly small in the experimental temperature range below 1 K at zero magnetic field [19,20] (see Methods), although an increase in nuclear contribution in the presence of a magnetic field makes the accurate determination of low temperature linear specific heat capacity in finite applied magnetic fields challenging (see Methods) [21].…”

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confidence: 99%

Fermi surface in the absence of a Fermi liquid in the Kondo insulator SmB6

et al. 2017

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“…These exotic states have been advocated to be present in triangular lattice organic materials 3-10 κ-(ET) 2 Cu 2 (CN) 3 11,12 , EtMe 3 Sb[Pd(dmit) 2 ] 2 13-15 and κ-H 3 (Cat-EDT-TTF) 2 16 , and Herberthsmithite 17 . More recently this state has also been advocated to be present in 1T-TaS 2 18,19 and a closely related state, known as the composite exciton Fermi liquid (CEFL), has been advocated to be present in correlated mixed valence materials like SmB 6 20,21 and YbB 12 22-24 allowing to understand some of their puzzling behavior [25][26][27][28] . This state has also been recently proposed in YbMgGaO 4 29-32 although several subsequent studies have challenged this proposal [33][34][35][36] .…”

Section: Introductionmentioning

confidence: 99%

Cyclotron resonance inside the Mott gap: A fingerprint of emergent neutral fermions

Rao

Sodemann

2019

Phys. Rev. B

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A major obstacle to identify exotic quantum phases of matter featuring spin-charge separation above one-dimension is the lack of tailored probes allowing to establish their presence in correlated materials. Here we propose an optoelectronic response that could allow to pinpoint the presence of certain spin-charge separated states with emergent neutral gapless fermions in two and threedimensional materials. We show that even though these states behave like insulators under static electric fields, they can display clear cyclotron resonance peaks in their light absorption spectrum under static magnetic fields, but typically the principal Kohn mode will be missing in comparison to ordinary metals. This distinctive phenomena could be tested in materials such as triangular lattice organics, three-dimensional mixed valence insulators YbB12 and SmB6, and transition metal dichalcogenides 1T-TaS2 and 1T-TaSe2.

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Specific heat of SmB6 at very low temperatures

Cited by 25 publications

References 7 publications

Anomalous three-dimensional bulk ac conduction within the Kondo gap of SmB6 single crystals

Anomalous three-dimensional bulk ac conduction within the Kondo gap of SmB6 single crystals

Fermi surface in the absence of a Fermi liquid in the Kondo insulator SmB6

Cyclotron resonance inside the Mott gap: A fingerprint of emergent neutral fermions

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