Extra Seminar - Würzburg ToCoTronics Colloquium

The metal-insulator transition (MIT), a fascinating phenomenon occurring  in some strongly correlated materials, is of central interest in modern  condensed-matter physics.  Controlling the MIT by external stimuli is a  key technological goal for applications in future electronic devices. However, the standard control by means of the field effect, which works extremely well for semiconductor transistors, faces severe difficultieswhen applied to the MIT [1].  Hence, a radically different approach is needed. In this talk, we report an MIT induced by resonant tunneling (RT) in double quantum well (QW) structures of strongly correlated oxides.  In our structures, two layers of the strongly correlated conductive oxide SrVO3 (SVO) sandwich a barrier layer of the band insulator SrTiO3 (STO).  The top QW is a marginal Mott-insulating SVO layer, while the bottom QW is a metallic SVO layer.  As the top marginal Mott-insulating QW, we used a 2-ML SVO layer which can easily become a metal by applying a small perturbation [2,3]. As a counterpart, we used a 6-ML SVO for the bottom metallic QW layer, so as to induce the RT effect between two energetically close QW states [3,4].  Angle-resolved photoemission spectroscopy experiments revealed that the top QW layer became metallized when the thickness of the tunneling barrier layer was reduced.  An analysis based on band structure calculations indicated that RT between the quantized states of the double QW induces the MIT. Our work opens avenues for realizing the RT-driven Mott transistor based on the wave-function engineering of strongly correlated electrons [5,6].

References

[1] C. H. Ahn et al., Rev. Mod. Phys. 78, 1185–1212 (2006).
[2] Z. Zhong et al., Phys. Rev. Lett. 114, 246401 (2015).
[3] M. Kobayashi, H.K. et al., Sci. Rep. 7, 16621 (2017).
[4] K. Yoshimatsu, H.K. et al., Science 333, 319–322 (2011).
[5] R. Yukawa, H.K. et al., Nat. Commun. 12, 7070 (2021).
[6] T. Kanda, H.K. et al., Commun. Mater. 4, 27 (2023).