Leena Aggarwal: Tip-induced Superconductivity

In this talk, I am going to present some of the work that I have done during my PhD. In the first part I will mostly focus on building a low-temperature Andreev reflection spectroscopy probe (which is basically a simpler version of an STM). In the second part, I will briefly talk about the observation of a new phase of matter, tip-induced superconductivity (TISC), that emerges only under mesoscopic metallic point contacts on topologically non-trivial semimetals like a 3-D Dirac semimetal Cd3As2, and a Weyl semimetal, TaAs and comment on the possible mechanism that might lead to the emergence of such a surprising phase of matter. All these experiments were done using our home-built low-temperature probe.
If time permits, I will also talk about some experiments that we did using various scanning probe based microscopic techniques, e.g., piezo-response force microscopy (PFM) and ferroelectric lithography. I will show how certain “artifacts” can limit the application of PFM in the investigation of ferroelectric materials, and how, under certain circumstances, such “artifacts” can actually turn out to be useful.

[1] L. Aggarwal, A. Gaurav, G. S. Thakur, Z. Haque, A. K. Ganguli & G. Sheet, Unconventional Superconductivity at Mesoscopic Point-contacts on the 3-Dimensional Dirac Semi-metal Cd3As2.” Nature Materials 15, 32 (2016).
[2] L. Aggarwal, S. Gayen, S. Das, R. Kumar, V. Sϋß, C. Shekhar, C. Felser & G. Sheet, “Mesoscopic superconductivity and high spin-polarization coexisting at metallic point contacts on Weyl semimetal TaAs.” Nature Communications, 8, 13974 (2017).
[3] J. S. Sekhon, L. Aggarwal & G. Sheet, “Voltage induced local hysteretic phase switching in silicon.” Applied Physics Letters 104, 162908 (2014).