Valence Fluctuating State in SmB₆

Abstract

Specific heat and transport properties are measured on good single crystals of SmB6. The specific heat experiment indicates that there is a gap of near 100 K in the 4f system leaving a very small T linear term. Conductivity experiment indicates that the usual hopping type conductivity changes to a constant value without activation which is, however, three orders of magnitude smaller than the so far believed minimum metallic conductivity. The usual Anderson localization proposed before by us is clearly not applicable. Here, we propose a model of a new type of the Wigner lattice formation. Various anomalous properties mentioned above are explained within this model

11B-NMR Study of SmB6under Pressure

“…Between 15 K and 5 K an in-gap band with activation energy E d ≈ 3-5 meV (situated below the conduction band) was observed by several experimental measurements [3][4][5]. Several models of in-gap states have been proposed [6][7][8], however the nature of the in--gap states is still under discussion. Below about 5 K the electrical conductivity is constant due to small conductivity channel in the E d band.…”

Electronic Structure of Mixed Valent Systems

“…However, the low-temperature transport properties of SmB 6 are manifestly metallic, having a large but finite resistivity below ≈ 4 K [ [83][84][85]. There is a considerable controversy whether these in-gap states are intrinsic and present in pristine SmB 6 [77][78][79][80]86,87], or extrinsic and dictated entirely by sample quality [83][84][85]88,89]. The size of the energy gap determined by different methods, varies considerably.…”

Low Temperature Transport and Magnetic Properties of SmB6

“…The resistivity p(T) is slightly temperature dependent down to 50 K below which it starts to increase exponentially [1,5] due to the opening of a hybridization gap in the density of states. Between 15 K and 5 K it can be described by an exponential increase p(T) α exp(-Δ 0 /kΒ Τ), with an activation energy Δ 0 of a few meV [1,[5][6][7][8][9]. However, there exists disagreement about the temperature dependence of p below about 4 K and about the origin of the observed residual conductivity.…”

“…However, there exists disagreement about the temperature dependence of p below about 4 K and about the origin of the observed residual conductivity. The residual conductivity has been interpreted in terms of the minimum conductivity [7], as a Wigner lattice formation [9], or attributed to surface states [10]. Thermally activated behavior and hopping transport have been proposed to account for the temperature dependence [5,9] in this temperature range.…”

“…The residual conductivity has been interpreted in terms of the minimum conductivity [7], as a Wigner lattice formation [9], or attributed to surface states [10]. Thermally activated behavior and hopping transport have been proposed to account for the temperature dependence [5,9] in this temperature range. The magnetic susceptibility reveals the characteristic features of an intermediate valence compound: a Curie-Weiss like susceptibility at temperatures above 100 K indicating a local-moment behavior, and a temperature independent susceptibility at low temperatures due to a nonmagnetic 4f 5 5d1 configuration between localized (419) 4f5 states and itinerant 5d 1 states \ [1].…”