| 研究概要 |
The aim of this project is to find new possibly unconventional superconductivity (SC) in so-called semiconducting and insulating materials induced by doping. As a starting point topological insulator materials were chosen. In this new class of materials firstly (Pb0.77Sn0.23)Se was targeted and doped with various elements. Tl doping was found to induce SC but after a comprehensive study of this particular doping series it was found that not the bulk phase but a minority phase was responsible for the SC and hence this system was given up.
The study of the superconducting topological insulator CuxBi2Se3, already started before this project, was continued by a specific-heat study of the x dependence of the superconducting phase. It seems that the system behaves different for small and large Cu concentrations x but the complex intercalation chemistry of this system makes an explanation of the possibly topological superconducting phase difficult. The second currently discussed possible topological superconducting system is more promissing: Sn1-xInxTe. SnTe exhibits a ferroelectric instability along with a structural phase transition. It was found that the superconducting phase of this system shows a peculiar In-doping dependence and that the superconducting pairing mechanism is possibly different in the ferroelectric phase below x ~0038 from that in the cubic phase. Moreover there are indications that close to the critical In concentration of x ~ 0.038 the SC may be unconventional whereas away from it in either direction the system seems to be “more” conventional.
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| 今後の研究の推進方策 |
In the next fiscal year I'd like to focus on newly found topological systems as, e.g., the recently emergent compound Cd3As2 which is discussed in terms of Dirac physics ("Weyl semimetal") and exhibits a very high electron mobility. Here also doping is indicated to possibly induce superconductivity. First the growth recipe has to be set which should be no problem for the parent material and some of the substitution series, e.g, Zn-doping, since the material has already been known for a long time. Before starting the growth several safety measures have to be taken into account. This has already started (preparing a suitable glove box, safe pelletizing and cutting, a.s.o.). Possibly additional items to handle Arsenic have to be bought.
The further research plan depends strongly on the results of the material synthesis and if there is a superconducting phase or not. Further potentially interesting materials include doped BiTeI and doped dichalcogenides.
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