Sobhit Singh (Rutgers)

February 19, 2021 @ 1:30 pm – 2:30 pm

Title: A proposal for determination of polarity orientation in polar metals

Host: Cyrus Dreyer

In typical ferroelectrics, which are polar insulators, switching of polarity is immediately manifested in a polarization switching current. By contrast, in a polar metal or semimetal, a corresponding experimental response is missing. In this talk, I will discuss that the nonlinear Hall effect (NLHE) can offer a way to detect the polarization orientation and polarization switching in polar metals and semimetals, as well as in narrow bandgap ferroelectric semiconductors, which often show conducting behavior due to the presence of defects and impurities. This effect is particularly enhanced in topological metals or topological semimetals due to the large concentrations in Berry curvature near the Fermi level, which is central to the description of the NLHE [1-2]. However, we find that NLHE can also be realized in topologically trivial materials. The nonlinear Hall response current, which appears as a second-order response to an external electric field, vanishes in the paraelectric phase and reverses its sign upon the polarity reversal in a polar metal [3]. The magnitude of this response current is large enough to be experimentally detected [4].

[1] I. Sodemann and L. Fu, Phys. Rev. Lett. 115, 216806 (2015).
[2] S. Singh, J. Kim, K. M. Rabe, and D. Vanderbilt, Phys. Rev. Lett. 125, 046402 (2020).
[3] R.-C. Xiao, D.-F. Shao, W. Huang, and H. Jiang, Phys. Rev. B 102, 024109 (2020).
[4] Ma et al., Nature 565, 337 (2019).

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