Optical conductivity of the Kondo insulator<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">YbB</mml:mi></mml:mrow><mml:mrow><mml:mn>12</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mo>:</mml:mo></mml:math> Gap formation and low-energy excitations

Okamura, Hidekazu; Kimura, S.; Shinozaki, H.; Nanba, Tetsuya; Iga, Fumitoshi; Shimizu, Nobujiro; Takabatake, Toshiro

doi:10.1103/physrevb.58.r7496

Cited by 86 publications

(110 citation statements)

References 20 publications

Supporting

Mentioning

100

Contrasting

Unclassified

Order By: Relevance

“…For example, for YbB 12 the low temperature conductivity vanishes below 25 meV, and then rises to a maximum in the mid-IR near 0.25 eV. 3 The experimental neutron scattering spectra of the Kondo insulators also show low temperature features whose energy scale is that of the gap. The intensity of these features is highly Q-dependent, peaking at the (1/2,1/2,1/2) zone boundary point in YbB 12 4 and SmB 6 .…”

mentioning

confidence: 99%

“…5 When the Fermi level is not in the gap, the behavior is that of an intermediate valence metal. The cubic (Cu 3 Au structure) compound YbAl 3 exhibits strong intermediate valence (z = 2.75) and a large Kondo temperature (T K ~ 600-700 K). Below the "coherence temperature" T coh ~ 40 K, where the resistivity exhibits the T 2 behavior expected for a Fermi liquid, 6 the optical conductivity exhibits 7 a narrow Drude resonance separated by a deep minimum at 30 meV from a mid-infrared peak at 0.25 eV.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Localized Excitation in the Hybridization Gap inYbAl3

et al. 2006

View full text Add to dashboard Cite

The intermediate valence compound YbAl 3 exhibits a broad magnetic excitation in the inelastic neutron scattering spectrum with characteristic energy E 1 ª 50 meV, equal to the Kondo energy (T K ~ 600-700 K). In the low temperature (T < T coh ~ 40 K) Fermi liquid state, however, a new peak in the scattering occurs at E 2 ≈ 33 meV, which lies in the hybridization gap that exists in this compound. We show, using inelastic neutron scattering on a single-crystal sample, that while the scattering at energies near E 1 has the momentum (Q-) dependence expected for interband scattering across the indirect gap, the scattering near E 2 is independent of Q over a large fraction of the Brillouin zone. A possible explanation is that the peak at E 2 arises from a spatially-localized excitation in the hybridization gap.61.12. Ex, 71.28.+d, 75.20.Hr

show abstract

mentioning

confidence: 99%

mentioning

confidence: 99%

Localized Excitation in the Hybridization Gap inYbAl3

et al. 2006

View full text Add to dashboard Cite

show abstract

“…Kondo insulators are "heavy fermion" materials whose quasiparticle excitations have band-insulating dynamics [1][2][3][4][5][6][7][8][9][10][11] . The most studied Kondo insulator is samarium hexaboride (SmB 6 ), but other similar materials are also known (e.g.…”

Section: Introductionmentioning

confidence: 99%

In-gap collective mode spectrum of the topological Kondo insulatorSmB6

Fuhrman

Nikolić

2014

Phys. Rev. B

View full text Add to dashboard Cite

Samarium hexaboride (SmB6) is the first strongly correlated material with a recognized nontrivial band-structure topology. Its electron correlations are seen by inelastic neutron scattering as a coherent collective excitation at the energy of 14 meV. Here we calculate the spectrum of this mode using a perturbative slave boson method. Our starting point is the recently constructed Anderson model that properly captures the band-structure topology of SmB6. Most self-consistent renormalization effects are captured by a few phenomenological parameters whose values are fitted to match the calculated and experimentally measured mode spectrum in the first Brillouin zone. A simple band-structure of low-energy quasiparticles in SmB6 is also modeled through this fitting procedure, because the important renormalization effects due to Coulomb interactions are hard to calculate by ab-initio methods. Despite involving uncontrolled approximations, the slave boson calculation is capable of producing a fairly good quantitative match of the energy spectrum, and a qualitative match of the spectral weight throughout the first Brillouin zone. We find that the "fitted" band-structure required for this match indeed puts SmB6 in the class of strong topological insulators. Our analysis thus provides a detailed physical picture of how the SmB6 band topology arises from strong electron interactions, and paints the collective mode as magnetically active exciton.

show abstract

“…Other Kondo insulators (e.g YbB 12 [22] or Ce 3 Bi 4 Pt 3 (T K ∼35K) [23] are "Pauli limited", with a gap that closes linearly in a field, closing at a critical field in the range B c ∼ 20 − 50T . By contrast, in SmB 6 , the much smaller size of the f-electron g-factor (g ∼ 0.1 − 0.2) suppresses the Zeeman splitting in favor of an orbital closure of the gap at a critical field in excess of 100T [24,25].…”

mentioning

confidence: 99%

Kondo Breakdown and Quantum Oscillations inSmB6

2016

View full text Add to dashboard Cite

Recent quantum oscillation experiments on SmB6 pose a paradox, for while the angular dependence of the oscillation frequencies suggest a 3D bulk Fermi surface, SmB6 remains robustly insulating to very high magnetic fields. Moreover, a sudden low temperature upturn in the amplitude of the oscillations raises the possibility of quantum criticality. Here we discuss recently proposed mechanisms for this effect, contrasting bulk and surface scenarios. We argue that topological surface states permit us to reconcile the various data with bulk transport and spectroscopy measurements, interpreting the low temperature upturn in the quantum oscillation amplitudes as a result of surface Kondo breakdown and the high frequency oscillations as large topologically protected orbits around the X point. We discuss various predictions that can be used to test this theory.SmB 6 , discovered 50 years ago [1,2], has attracted recent interest due to its unusual surface transport properties: while its insulating gap develops around T K 50K, the resistivity saturates below a few Kelvin[3]. The renewed interest derives in part from from the possibility that SmB 6 is a topological Kondo insulator, developing topologically protected surface states at low temperatures [4][5][6][7]. Experiments [8][9][10] have confirmed that the plateau conductivity derives from surface states, and these states have been resolved by angle-resolved photoemission spectroscopy (ARPES) [11][12][13][14]. Furthermore, spin-ARPES experiments have revealed the spinmomentum locking of the surface quasiparticles expected from topologically protected Dirac cones [15].Yet despite this progress, some important experimental results are unresolved. In particular, quantum oscillation experiments on SmB 6 have given rise to two dramatically different interpretations [16,17]. Ref [16] observes low frequency (small Fermi surface) oscillations with the characteristic 1/ cos(φ) dependence on field orientation expected from 2D topological surface states. On the other hand Ref [17] detects a wide range of frequencies (both high and low frequency oscillations) which have been interpreted in terms of angularly isotropic three dimensional quasiparticle orbits, resembling a metallic hexaboride without a hybridization gap (such as LaB 6 ). A striking aspect of these measurements, is that the oscillations strongly deviate from a classic Lifshitz-Kosevich formula below ∼ 1K. Two recent theoretical proposals have been advanced to account for this bulk behavior, as a consequence of magnetic breakdown [18], of the formation of non-conducting Fermi surfaces [19].Another aspect of recent measurements, is the wide disparity in the reported effective masses of the carriers. The effective mass observed in both quantum oscillation experiments, m * /m ∼ 0.1 − 0.2 is an order of magnitude smaller than effective mass observed in ARPES [11][12][13][14] [17]. Error bars are the size of symbols which include both experimental errorbars and also errors from extracting data from a logarithmic plot. Given...

show abstract

Optical conductivity of the Kondo insulatorYbB12: Gap formation and low-energy excitations

Cited by 86 publications

References 20 publications

Localized Excitation in the Hybridization Gap inYbAl3

Localized Excitation in the Hybridization Gap inYbAl3

In-gap collective mode spectrum of the topological Kondo insulatorSmB6

Kondo Breakdown and Quantum Oscillations inSmB6

Contact Info

Product

Resources

About