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Precision Control of Superconductivity in Atomic Layers Using Magnetic Molecules

—The Key Is the Manipulation of “Hidden Degrees of Freedom” in Molecules—

National Institute for Materials Science (NIMS)
School of Engineering, University of Tokyo
Institute for Molecular Science (IMS), National Institutes of Natural Sciences (NINS)
Chiba University

A joint research team consisting of NIMS, University of Tokyo, NINS, and Chiba University succeeded in precisely controlling the transition temperature of atomic-scale-thick superconductors using magnetic organic molecules. The team also identified the control mechanism. (“Controlled Modification of Superconductivity in Epitaxial Atomic Layer–Organic Molecule Heterostructures”, Shunsuke Yoshizawa, Emi Minamitani, Saranyan Vijayaraghavan, Puneet Mishra, Yasumasa Takagi, Toshihiko Yokoyama, Hiroaki Oba, Jun Nitta, Kazuyuki Sakamoto, Satoshi Watanabe, Tomonobu Nakayama, and Takashi Uchihashi, Nano Lett., 2017, 17 (4), pp 2287–2293, DOI: 10.1021/acs.nanolett.6b05010)

Abstract

  1. A research team led by Shunsuke Yoshizawa, ICYS researcher, NIMS, Takashi Uchihashi, leader of the Surface Quantum Phase Materials Group, MANA, NIMS, Emi Minamitani, assistant professor, School of Engineering, University of Tokyo, Toshihiko Yokoyama, professor, IMS, NINS, and Kazuyuki Sakamoto, professor, Graduate School of Advanced Integration Science, Chiba University, succeeded in precisely controlling the transition temperature of atomic-scale-thick superconductors using magnetic organic molecules. The team also identified the control mechanism.
  2. Atomic layer materials, including graphene, have been actively studied in recent years. In particular, much attention has been drawn to discoveries of superconducting atomic layer materials with a high transition temperature. These materials are superior to bulk materials in that their superconducting properties can be controlled through carrier doping of their surfaces/interfaces. However, it had been difficult to understand the mechanism of carrier doping at the microscopic level.
  3. The research team recently succeeded for the first time in precisely controlling the transition temperature of superconducting atomic layers using organic molecules. To achieve this, the team fabricated an ideal heterostructure consisting of a superconducting atomic layer and a layer of highly ordered organic molecules on top of the atomic layer. The creation of the heterostructure enabled the team to perform a detailed study on the mechanism behind the doping of atomic layer materials. Consequently, the analysis revealed that the metal atoms at the center of the organic molecules retained electron spins , which could generate magnetism. In addition, the team found that change in superconducting transition temperature is strongly influenced by competition between electron charge and spin in the organic molecules. Moreover, the team discovered that the spin effect is governed by the direction of electron orbitals, which can be viewed as “hidden degrees of freedom” in molecules.
  4. In light of these results, we aim to greatly enhance superconducting properties, i.e. superconducting transition temperature, of these heterostructures . After such enhancement is made, we hope to apply superconducting materials in a wide variety of fields in a manner so that the technology will help ease environmental/energy issues and support the sustainable development of society.
  5. This study was conducted in conjunction with the following programs/projects: the MEXT WPI program, a project titled “Manifestation and control of superconductivity in surface superstructures on semiconductors” (Takashi Uchihashi, principal investigator) funded by the JSPS Grant-in-Aid for Scientific Research (A), a project titled “Search for Rashba-type superconductors in surface alloy atomic layers” (Shunsuke Yoshizawa, principal investigator) funded by the JSPS Grant-in-Aid for Young Scientists (B), and the MEXT Nanotechnology Platform Japan program.
  6. This study was published in Nano Letters, an American Chemical Society journal, on March 30, 2017.

"Figure. (a) Schematic diagram of a heterostructure comprising organic molecules and a superconducting atomic layer. (b)-(d) Scanning tunneling microscope images of samples. (b) Indium atomic layer (superconducting layer). (c) Phthalocyanine molecular layer grown on the indium atomic layer (manganese atom at the center of each molecule). (d) Phthalocyanine molecular layer grown on the indium atomic layer (copper atom at the center of each molecule)." Image

Figure. (a) Schematic diagram of a heterostructure comprising organic molecules and a superconducting atomic layer. (b)-(d) Scanning tunneling microscope images of samples. (b) Indium atomic layer (superconducting layer). (c) Phthalocyanine molecular layer grown on the indium atomic layer (manganese atom at the center of each molecule). (d) Phthalocyanine molecular layer grown on the indium atomic layer (copper atom at the center of each molecule).




Contacts

(General questions about this research)
Takashi Uchihashi
Group Leader, Surface Quantum Phase Materials Group, MANA, National Institute for Materials Science
Tel: +81-29-860-4150
E-Mail: UCHIHASHI.Takashi=nims.go.jp
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(Regarding theoretical calculations)
Emi Minamitani
Department of Materials Engineering, University of Tokyo
Tel: +81-3-5841-1286
E-Mail: eminamitani=cello.t.u-tokyo.ac.jp
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(Regarding the synchrotron radiation facility and Nanotechnology Platform Program)
Toshihiko Yokoyama
Professor, Electronic Structure, Materials Molecular Science, Institute for Molecular Science, National Institutes of Natural Sciences
Tel: +81-564-55-7345
E-Mail: yokoyama=ims.ac.jp
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(Regarding photoelectron spectroscopy measurements)
Kazuyuki Sakamoto
Professor, Graduate School of Advanced Integration Science, Chiba University
Tel: +81-43-290-3924
E-Mail: kazuyuki_sakamoto=faculty.chiba-u.jp
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(For general inquiries)
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Public Relations Office
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Shogo Sakamoto
Graduate School & Faculty of Engineering
Tel: +81-43-290-3044
E-Mail: mah3034=office.chiba-u.jp
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National Institute for Materials Science (NIMS)
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