Abstract
We show that Cs intercalated bilayer graphene acts as a substrate for the growth of a strained Cs film hosting quantum well states with high electronic quality. The Cs film grows in an fcc phase with a substantially reduced lattice constant of 4.9 Å corresponding to a compressive strain of 11% compared to bulk Cs. We investigate its electronic structure using angle-resolved photoemission spectroscopy and show the coexistence of massless Dirac and massive Schrödinger charge carriers in two dimensions. Analysis of the electronic self-energy of the massive charge carriers reveals the crystallographic direction in which a two-dimensional Fermi gas is realized. Our work introduces the growth of strained metal quantum wells on intercalated Dirac matter.
Highlights
We show that Cs intercalated bilayer graphene acts as a substrate for the growth of a strained Cs film hosting quantum well states with high electronic quality
The low energy electron diffraction (LEED) pattern of epitaxial bilayer graphene on Ir(111) is shown in Fig. 1a and shows six diffraction spots with a very weak moiré pattern
We note that for angle-resolved photoemission spectroscopy (ARPES) and Raman, the synthesized sample had a complete bilayer coverage while for the scanning tunneling microscopy (STM) measurements shown in Fig. 1b, the bilayer coverage was chosen about 50%
Summary
We show that Cs intercalated bilayer graphene acts as a substrate for the growth of a strained Cs film hosting quantum well states with high electronic quality. Its development can have a large impact on electronic structure engineering of 2D matter and extend growth techniques that use van-der-Waals materials as substrates. We introduce an epitaxial growth method for the synthesis of crystalline and strained alkali-metal films on top of bilayer graphene. Graphene hosts ordered layers of alkali metals either adsorbed onto[11] or intercalated in between individual graphene sheets[12] or between the substrate and graphene[13]. Other metals than the alkali metals do not realize a Fermi gas because of interactions, e.g., hybridization, electron–electron, and electron–phonon coupling, as evidenced by deviations from the parabolic free electron like band structure[17,18]
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