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Realization of a hole-doped Mott insulator on a triangular silicon lattice and its zero-bias-anomaly

Speaker: Dr. MING Fangfei
The University of Tenneessee,Knoxville
Time: 2018-01-19 10:00
Place: ROOM 9004, Hefei National Laboratory Building


  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 magneto-resistance, and high-temperature superconductivity in layered perovskite compounds. Advances in this field would greatly benefit from the availability of new material systems with similar richness of physical phenomena, but with fewer chemical and structural complications in comparison to oxides. Using scanning tunneling microscopy and spectroscopy (STM/STS), we show that such a system can be realized on a silicon platform. 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 quasi-particle states at the Fermi level, well-defined Fermi contour segments, and a sharp singularity in the density of states. We further show that the maximum hole-density of this system increases with decreasing domain size as the area of the Mott insulating domains approaches the nanoscale regime. Concomitantly, STS data at 4.4 K reveal an increasingly prominent zero bias anomaly (ZBA). We consider two different scenarios as potential mechanisms for this ZBA: chiral d_(x^2 〖-y〗^2 )+ id_xy wave superconductivity and a dynamical Coulomb blockade (DCB) effect. With a thorough experimental characterization, we conclude that the ZBA is predominantly due to a DCB effect, while a superconducting instability is absent or a minor contributing factor.
[1] F. Ming, et. al., PRL 119, 266802 (2017)
[2] F. Ming, et. al., arXiv:1712.02736 (to be published in PRB)

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