Academic Affiliation: Leiden University, Netherlands

Research Area: Develop and use novel techniques for STM to investigate quantum matter.

Talk date: January 21, 2020

Charge trapping and super-Poissonian noise centers in a cuprate superconductor

In this talk I will present new insight into the mystery of highly anisotropic transport in a cuprate high-temperature superconductor and show that these materials can trap additional charges. Above the superconducting transition these materials are perfectly metallic along the crystal planes (ab-plane), but are insulating in the c-axis, with ratios between in-plane and perpendicular resistance exceeding 104. This anisotropy has been identified as one of the key mysteries in the cuprates and has been connected to the mechanism of high-temperature superconductivity. I will show how we employ our newly developed scanning noise spectroscopy technique, for which we combined a scanning tunneling microscope (STM) with a novel MHz frequency amplifier to bring noise-spectroscopy measurements to the atomic scale
[1]. We discover surprisingly large deviations from the expected Poissonian noise of uncorrelated electron transport in this strongly correlated material. A behavior that is familiar from highly polarizable insulators and represents strong evidence for trapping of charge in the charge reservoir layers of the cuprates. Our measurements suggest a picture of metallic layers separated by polarizable insulators within a three-dimensional superconducting state. We will show how these new observations connect to the mystery of the anisotropic transport in this high-temperature superconductor, shedding new light onto this issue [2].

References:
[1] K.M. Bastiaans et al. Rev. Sci. Instrum. 89, 093709 (2018).
[2] K.M. Bastiaans et al. Nature Physics 14, 1183 (2018).