Planar Tunneling Spectroscopy of SmB<sub>6</sub> Thin Films
ORAL
Abstract
Samarium hexaboride (SmB₆) is a promising candidate as a topological Kondo insulator (TKI), where strong electronic correlations lead to hybridization between localized 4f and itinerant 5d states. This results in a large bulk hybridization gap and robust metallic surface states at low temperatures. [1]
In our previous work, we successfully synthesized planar tunnel junctions on SmB₆ single crystals by utilizing self-oxidation of Sm-deficient surfaces. [2] Planar tunnelling spectroscopy (PTS) revealed a Dirac-like, linear conductance that did not persist across the entire bulk insulating hybridization gap and asymmetric characteristics. Using second-harmonic detection, we find asymmetric features at ±1 meV that emerge at low temperature, concomitant with the formation of the conducting surface states.
To spectroscopically probe the TSS in confined geometries, we have extended our PTS studies to high-quality SmB₆ thin films. The films are grown by co-sputtering Sm and B, and planar tunnel junctions are fabricated via self-oxidation of the thin film surface. The XRD, AFM, and transport data along with the presence of surface states indicates the high quality of these thin films. The tunneling conductance measurements on these junctions allow direct comparison with those on single-crystal SmB₆, providing new insights into the evolution of the robust surface states under confinement.
[1]. M. Dzero,et al., Phys. Rev. Lett. 104, 106408 (2010)
[2]. W.K. Park, et al., PNAS 113, 24 (2016)
In our previous work, we successfully synthesized planar tunnel junctions on SmB₆ single crystals by utilizing self-oxidation of Sm-deficient surfaces. [2] Planar tunnelling spectroscopy (PTS) revealed a Dirac-like, linear conductance that did not persist across the entire bulk insulating hybridization gap and asymmetric characteristics. Using second-harmonic detection, we find asymmetric features at ±1 meV that emerge at low temperature, concomitant with the formation of the conducting surface states.
To spectroscopically probe the TSS in confined geometries, we have extended our PTS studies to high-quality SmB₆ thin films. The films are grown by co-sputtering Sm and B, and planar tunnel junctions are fabricated via self-oxidation of the thin film surface. The XRD, AFM, and transport data along with the presence of surface states indicates the high quality of these thin films. The tunneling conductance measurements on these junctions allow direct comparison with those on single-crystal SmB₆, providing new insights into the evolution of the robust surface states under confinement.
[1]. M. Dzero,et al., Phys. Rev. Lett. 104, 106408 (2010)
[2]. W.K. Park, et al., PNAS 113, 24 (2016)
*This work was performed at the National High Magnetic Field Laboratory, which is supported by the National Science Foundation Cooperative Agreement No. DMR-2128556 and the State of Florida. Jennifer Reid is supported by the NHMFL Crow-Schuler Postdoctoral Fellowship (State-of-Florida). We also acknowledge support by NSF/DMR-2003405 & NSF grant DMR-1847887.
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Presenters
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Mohammad Irfan
- National High Magnetic Field Laboratory & Florida State University
- Florida State University
- Florida State University, National High Magnetic Field Laboratory