Electrical Conductivity through a Single Atomic Step Measured with the Proximity-Induced Superconducting Pair Correlation

Howon Kim, Shi-Zeng Lin, Matthias J. Graf, Yoshinori Miyata, Yuki Nagai, Takeo Kato, and Yukio Hasegawa

Phys. Rev. Lett. 117, 116802 – Published 8 September 2016

Abstract

Local disordered nanostructures in an atomically thick metallic layer on a semiconducting substrate play significant and decisive roles in transport properties of two-dimensional (2D) conductive systems. We measured the electrical conductivity through a step of monoatomic height in a truly microscopic manner by using as a signal the superconducting pair correlation induced by the proximity effect. The transport property across a step of a one-monolayer Pb surface metallic phase, formed on a Si(111) substrate, was evaluated by inducing the pair correlation around the local defect and measuring its response, i.e., the reduced density of states at the Fermi energy using scanning tunneling microscopy. We found that the step resistance has a significant contribution to the total resistance on a nominally flat surface. Our study also revealed that steps in the 2D metallic layer terminate the propagation of the pair correlation. Superconductivity is enhanced between the first surface step and the superconductor–normal-metal interface by reflectionless tunneling when the step is located within a coherence length.

Received 9 April 2016

DOI:https://doi.org/10.1103/PhysRevLett.117.116802

Physics Subject Headings (PhySH)

Electrical conductivity Proximity effect Superconductivity

Interfaces

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Howon Kim^1,*, Shi-Zeng Lin², Matthias J. Graf^2,†, Yoshinori Miyata¹, Yuki Nagai³, Takeo Kato¹, and Yukio Hasegawa^1,‡

¹The Institute for Solid State Physics, The University of Tokyo, 5-1-5, Kashiwa-no-ha, Kashiwa 277-8581 Japan
²Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
³CCSE, Japan Atomic Energy Agency, Kashiwa, Chiba 277-8587, Japan

^*Present address: Department of Physics, University of Hamburg, D-20355 Hamburg, Germany.
^†Present address: Office of Science, U.S. Department of Energy, Washington, DC 20585-1290, USA.
^‡hasegawa@issp.u-tokyo.ac.jp