Realization of a Hole-Doped Mott Insulator on a Triangular Silicon Lattice

Abstract

The physics of doped Mott insulators is at the heart of some of the most exotic physical phenomena in materials research including insulator-metal transitions, colossal magnetoresistance, and high-temperature superconductivity in layered perovskite compounds. Advances in this field would greatly benefit from the availability of new material systems with a similar richness of physical phenomena but with fewer chemical and structural complications in comparison to oxides. Using scanning tunneling microscopy and spectroscopy, we show that such a system can be realized on a silicon platform. The adsorption of one-third monolayer of Sn atoms on a Si(111) surface produces a triangular surface lattice with half filled dangling bond orbitals. Modulation hole doping of these dangling bonds unveils clear hallmarks of Mott physics, such as spectral weight transfer and the formation of quasiparticle states at the Fermi level, well-defined Fermi contour segments, and a sharp singularity in the density of states. These observations are remarkably similar to those made in complex oxide materials, including high-temperature superconductors, but highly extraordinary within the realm of conventional sp-bonded semiconductor materials. It suggests that exotic quantum matter phases can be realized and engineered on silicon-based materials platforms.

Unconventional superconductivity in the extended Hubbard model: Weak-coupling renormalization group

“…Nonetheless, as a first guess, the one-orbital scenario might give a reasonable answer. Moreover, there is recent interest in certain adatom systems such as X/Ge(111) and X/Si(111) (X=Sn,Pb) [29][30][31][32][33][34][35] with the surface atoms forming a triangular net; Sn/Si(111) has recently even been claimed to show superconductivity at low temperatures [36]. These systems are well-described by one-band Hubbard models.…”

Formation of Sn‐Induced Nanowires on Si(557)

“…Recently, Ming et al succeeded in doping the α ‐Sn/Si(111) phase via changing the substrate's doping level. Upon hole doping, STS measurements show the development of a quasi‐particle state inside the Mott‐insulating gap of the system.…”

“…For instance, doping leads to various phases like high‐temperature superconductivity, charge‐transfer insulators, or robust metallic states . For α ‐Sn on Si(111) a metallic quasi‐particle state was found within the Mott gap, if the system is modified by means of the acceptor concentration of the Si substrate . In this context, the growth of Mott‐phases of finite widths is interesting and was not considered before.…”

Coupled Sublattice Melting and Charge-Order Transition in Two Dimensions

“…The temperature of the Sn√3 substrate surface was kept below 120 K and the pressure was better than 2x10 -10 mbar. The Sn√3 reconstruction consists of a triangular array of Sn adatoms that are located at T4 adsorption sites of the Si(111) surface (16)(17)(18). The areal Sn coverage is 1/3 monolayer (ΘSn = 1/3ML).…”

“…Its preparation has been described in detail in Ref. 18. To ensure the consistency of the results, we repeated the experiments on different Si(111) substrates, including heavily-doped n-type substrates (As-doped; 0.002 Ωcm), moderately doped p-type substrates (B-doped; 0.02 Ωcm), and heavily-doped p-type substrates (B-doped; 0.001 Ωcm).…”