  In recent years, the study on the Kondo insulator SmB6, a strongly correlated
electron material with decades-long puzzles, has become one of the most
attractive topics again because the discovery of the coexistence of its unusual
metallic surface state with an insulating bulk. Many efforts have been made in
understanding the corresponding physics behind in SmB6, but some puzzles on it,
being hotly debated and argued, has not been solved. In this article, based on
the latest progress in our high pressure studies and the accumulating results
reported by other groups on SmB6, we propose a notion named as accompany-type
valence fluctuation state, which possibly coexists with the Kondo ground state
of SmB6. The purpose of this article is to search a common starting point from
which most of the accumulated low-temperature phenomena observed by different
experimental investigations on SmB6 could be understood in a unified way.
Although this notion is only our personal understanding from a phenomenological
point of view and may be immature, anyway, we expect that this notion could
attract rigorous theoretical interpretations and further experimental
investigations, or stimulate better thinking on the physics in SmB6.
