Roles of the Narrow Electronic Band near the Fermi Level in 1T-TaS${}_2$-Related Layered Materials

Abstract

Here we use low-temperature scanning tunneling microscopy and spectroscopy (STM/STS) to reveal the roles of the narrow electronic band in two 1T-TaS${}_2$-related materials (bulk 1T-TaS${}_2$ and 4Hb-TaS${}_2$). 4Hb-TaS${}_2$ is a superconducting compound with alternating 1T-TaS${}_2$ and 1H-TaS${}_2$ layers, where the 1H-TaS${}_2$ layer has weak charge density wave (CDW) pattern and reduces the CDW coupling between the adjacent 1T-TaS${}_2$ layers. In the 1T-TaS${}_2$ layer of 4Hb-TaS${}_2$, we observe a narrow electronic band located near Fermi level, and its spatial distribution is consistent with the tight-binding calculations for two-dimensional 1T-TaS${}_2$ layers. The weak electronic hybridization between the 1T-TaS${}_2$ and 1H-TaS${}_2$ layers in 4Hb-TaS${}_2$ shifts the narrow electronic band to be slightly above the Fermi level, which suppresses the electronic correlation induced band splitting. In contrast, in bulk 1T-TaS${}_2$, there is an interlayer CDW coupling induced insulating gap. In comparison with the spatial distributions of the electronic states in bulk 1T-TaS${}_2$ and 4Hb-TaS${}_2$, the insulating gap in bulk 1T-TaS${}_2$ results from the formation of a bonding band and an antibonding band due to the overlap of the narrow electronic bands in the dimerized 1T-TaS${}_2$ layers.

5 pages, 4 figures

References in corpus (1)

• Band insulator to Mott insulator transition in 1T-TaS${}_2$

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