Localized trimers inducing metallic states in sub-monolayer thin Bi films on InSb(111)A

Low-dimensional topological states have transformed our understanding of charge transportation through quantum materials. Many relevant observations have been connected to bismuth (Bi) containing materials or ultrathin Bi films. Here, we studied sub-monolayer amounts of Bi deposition on the In-terminated InSb(111)A surface using various complementary surface science techniques. Bi deposition at elevated sample temperature results in well-ordered <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mo>(</a:mo><a:mn>2</a:mn><a:mo>×</a:mo><a:mn>2</a:mn><a:mo>)</a:mo></a:mrow></a:math> and <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:mrow><b:mo>(</b:mo><b:mn>2</b:mn><b:mi>√</b:mi><b:mn>3</b:mn><b:mo>×</b:mo><b:mn>2</b:mn><b:mi>√</b:mi><b:mn>3</b:mn><b:mo>)</b:mo></b:mrow><b:mtext>−</b:mtext><b:mi mathvariant="normal">R</b:mi><b:msup><b:mn>30</b:mn><b:mo>∘</b:mo></b:msup></b:mrow></b:math> surface reconstructions. Scanning tunneling microscopy/spectroscopy (STM/S) data show an enhanced density of states at the interface of the two reconstructions and local Bi trimers over the <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mrow><d:mo>(</d:mo><d:mn>2</d:mn><d:mo>×</d:mo><d:mn>2</d:mn><d:mo>)</d:mo></d:mrow></d:math> reconstructed surface. Bi-induced metallic surface states crossing the Fermi level are observed and attributed exclusively to the localized trimer states through STS and angle-resolved photoemission spectroscopy (ARPES) results. Furthermore, the ARPES spectra show band splitting at the Γ point and degenerate surface states at the M point, which is associated with Rashba splitting due to strong Bi-substrate interaction. Thus we interpret the Bi/InSb(111)A, exhibiting spin-split metallic surface states induced by localized Bi structures, as a promising candidate for exploring low-dimensional states and spin dynamics in future quantum materials.