Bulk and in-gap states in SmB6 revealed by high-field magnetotransport

Abstract

We report on temperature-dependent magnetotransport experiments of SmB 6 single crystals in high magnetic fields up to 33 T. Above the low-temperature plateau region in the zero-field resistivity, we find two distinct gapped regimes. The first is characterized by a temperature-independent gap 2 that closes in the presence of a high magnetic field while the second regime, above ∼8 K, features an energy gap 1 that is temperature dependent. In the entire temperature range, we observe an overall negative magnetoresistance that does not depend on the orientation of the crystalline plane with respect to the applied magnetic field with a maximum value at T ∼ 6.2 K. The regime of in-gap states is characterized by a low mobility, an anomalously high carrier concentration, and an enhanced nonlocal resistance that exceeds the expected classical value for a two-dimensional metallic conductor. Overall, our data can be interpreted in terms of a transition from bulk to in-gap dominated transport, but evidence of topological surface states is not observed.

Intrinsic Low-Temperature Magnetism in SmB6

“…Combined with the lower value E a ∼ 1 meV determined from 60 kOe transversefield µSR measurements of the relaxation rate in similar Al-flux grown single crystals [24], these results are compatible with the field-dependent contribution to the 11 B NMR spin-lattice relaxation rate -which has been explained by in-gap magnetic states separated from the conduction band by a 2.6 meV gap that shrinks with increasing field and closes by 140 kOe [20]. An ∼ 2.6 meV zero-field gap has also been observed by magnetotransport measurements [37], and in the low-energy electrodynamic response spectra of SmB 6 in the far-infrared range [38]. A 2.6 meV magnetic exciton is predicted to arise from a competition between the magnetic 4f 5 and nonmagnetic 4f 6 multiplets [39].…”

Metallic surface states in a correlated d-electron topological Kondo insulator candidate FeSb 2

“…common features that are key ingredients for such an exotic insulating state. Furthermore, the measurement of QOs at high magnetic fields in SmB 6 and YbB 12 is complicated by a fieldinduced gap collapse, with the transport gap closing at 85-100 T (36,37) and 50 T (38), respectively. For FeSb 2 , the transport gap is larger than the 4f compounds, and less likely to be prone to field-induced gap closing (SI Appendix, section S10).…”

Highly Asymmetric Nodal Semimetal in Bulk SmB6

“…FIG.3:(a), The real component of the reconstructed electronic dispersion ε k for F0 = 330 T and m * 0 ≈ 0.18 me (where me is the free electron mass), as for the small ρ ellipsoids in SmB6,10 for which we have v0 ≈ 640,000 ms −1 , k0 ≈ 1.00 × 10 9 m −1 and ε0 ≈ 21 meV. We use ∆ε = 2 meV,26 and λ = 800 Å, which yields Γ0 = |v 0 | λ ≈ 5.3 meV. (b), An expanded view of the electronic dispersion for the same F , m * and ∆ε, but for different values of λ. λ = 800 Å corresponds to the situation in which Γ02V , λ = 120 Å corresponds to the situation in which Γ0 2V , λ = 80 Å corresponds to the situation in which Γ0 2V , and λ = 40 Å corresponds to the situation in which Γ02V .…”