start-ver=1.4 cd-journal=joma no-vol=13 cd-vols= no-issue=1 article-no= start-page=537 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2023 dt-pub=20230111 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Semiconductor-metal transition in Bi2Se3 caused by impurity doping en-subtitle= kn-subtitle= en-abstract= kn-abstract=Doping a typical topological insulator, Bi2Se3, with Ag impurity causes a semiconductor-metal (S-M) transition at 35 K. To deepen the understanding of this phenomenon, structural and transport properties of Ag-doped Bi2Se3 were studied. Single-crystal X-ray diffraction (SC-XRD) showed no structural transitions but slight shrinkage of the lattice, indicating no structural origin of the transition. To better understand electronic properties of Ag-doped Bi2Se3, extended analyses of Hall effect and electric-field effect were carried out. Hall effect measurements revealed that the reduction of resistance was accompanied by increases in not only carrier density but carrier mobility. The field-effect mobility is different for positive and negative gate voltages, indicating that the E-F is located at around the bottom of the bulk conduction band (BCB) and that the carrier mobility in the bulk is larger than that at the bottom surface at all temperatures. The pinning of the E-F at the BCB is found to be a key issue to induce the S-M transition, because the transition can be caused by depinning of the E-F or the crossover between the bulk and the top surface transport. en-copyright= kn-copyright= en-aut-name=UchiyamaTakaki en-aut-sei=Uchiyama en-aut-mei=Takaki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=GotoHidenori en-aut-sei=Goto en-aut-mei=Hidenori kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=UesugiEri en-aut-sei=Uesugi en-aut-mei=Eri kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=TakaiAkihisa en-aut-sei=Takai en-aut-mei=Akihisa kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=ZhiLei en-aut-sei=Zhi en-aut-mei=Lei kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=MiuraAkari en-aut-sei=Miura en-aut-mei=Akari kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=HamaoShino en-aut-sei=Hamao en-aut-mei=Shino kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=EguchiRitsuko en-aut-sei=Eguchi en-aut-mei=Ritsuko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= en-aut-name=OtaHiromi en-aut-sei=Ota en-aut-mei=Hiromi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=9 ORCID= en-aut-name=SugimotoKunihisa en-aut-sei=Sugimoto en-aut-mei=Kunihisa kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=10 ORCID= en-aut-name=FujiwaraAkihiko en-aut-sei=Fujiwara en-aut-mei=Akihiko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=11 ORCID= en-aut-name=MatsuiFumihiko en-aut-sei=Matsui en-aut-mei=Fumihiko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=12 ORCID= en-aut-name=KimuraKoji en-aut-sei=Kimura en-aut-mei=Koji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=13 ORCID= en-aut-name=HayashiKouichi en-aut-sei=Hayashi en-aut-mei=Kouichi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=14 ORCID= en-aut-name=UenoTeppei en-aut-sei=Ueno en-aut-mei=Teppei kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=15 ORCID= en-aut-name=KobayashiKaya en-aut-sei=Kobayashi en-aut-mei=Kaya kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=16 ORCID= en-aut-name=AkimitsuJun en-aut-sei=Akimitsu en-aut-mei=Jun kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=17 ORCID= en-aut-name=KubozonoYoshihiro en-aut-sei=Kubozono en-aut-mei=Yoshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=18 ORCID= affil-num=1 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=2 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=3 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=4 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=5 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=6 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=7 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=8 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=9 en-affil=Advanced Science Research Center, Okayama University kn-affil= affil-num=10 en-affil=Faculty of Science and Engineering, Kindai University kn-affil= affil-num=11 en-affil=Department of Nanotechnology for Sustainable Energy, Kwansei Gakuin University kn-affil= affil-num=12 en-affil=Institute for Molecular Science, UVSOR Synchrotron Facility kn-affil= affil-num=13 en-affil=Department of Physical Science and Engineering, Nagoya Institute of Technology kn-affil= affil-num=14 en-affil=Department of Physical Science and Engineering, Nagoya Institute of Technology kn-affil= affil-num=15 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=16 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=17 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=18 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= END start-ver=1.4 cd-journal=joma no-vol= cd-vols= no-issue= article-no= start-page= end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2021 dt-pub=2021 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Hole doping and chemical pressure effects on the strong coupling superconductor PdTe en-subtitle= kn-subtitle= en-abstract= kn-abstract=Chemical doping of known superconductors is a probate strategy to test and enhance our understanding of which parameters control the critical temperature T-c and the critical magnetic fields. The transition metal chalcogenide PdTe is considered a conventional type II superconductor but its resilience to magnetic Fe doping is noteworthy. Isoelectronic Ni doping has been performed, but the effects of doping charges into PdTe have been so far unexplored. We follow two strategies to introduce holes into PdTe and to exert chemical pressure on it: by pnictogen doping on the chalcogen site PdTe1-xSbx and by systematically introducing a Pd deficiency in Pd1-yTe. We find that the superconducting T-c is very sensitive to both kinds of doping. We employ density functional theory to rationalize the observations. We conclude that in PdTe, the effects of charge doping take the lead but we can also identify a structural parameter that correlates with T-c. en-copyright= kn-copyright= en-aut-name=ChenLi en-aut-sei=Chen en-aut-mei=Li kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=IdeAndo en-aut-sei=Ide en-aut-mei=Ando kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=JeschkeHarald O. en-aut-sei=Jeschke en-aut-mei=Harald O. kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=KobayashiKaya en-aut-sei=Kobayashi en-aut-mei=Kaya kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= affil-num=1 en-affil=Graduate School of Science and Technology kn-affil= affil-num=2 en-affil=Graduate School of Science and Technology kn-affil= affil-num=3 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=4 en-affil=Graduate School of Science and Technology kn-affil= END start-ver=1.4 cd-journal=joma no-vol=101 cd-vols= no-issue=24 article-no= start-page=245111 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2020 dt-pub=20200602 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Magnetotransport properties of tellurium under extreme conditions en-subtitle= kn-subtitle= en-abstract= kn-abstract=This study investigates the transport properties of a chiral elemental semiconductor tellurium (Te) under magnetic fields and pressure. Application of hydrostatic pressure reduces the resistivity of Te, while its temperature dependence remains semiconducting up to 4 GPa, contrary to recent theoretical and experimental studies. Application of higher pressure causes structural as well as semiconductor-metal transitions. The resulting metallic phase above 4 GPa exhibits superconductivity at 2 K along with a noticeable linear magnetoresistance effect. On the other hand, at ambient pressure, we identified metallic surface states on the as-cleaved (10¯10) surfaces of Te. The nature of these metallic surface states has been systematically studied by analyzing quantum oscillations observed in high magnetic fields. We clarify that a well-defined metallic surface state exists not only on chemically etched samples that were previously reported, but also on as-cleaved ones. en-copyright= kn-copyright= en-aut-name=AkibaKazuto en-aut-sei=Akiba en-aut-mei=Kazuto kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=KobayashiKaya en-aut-sei=Kobayashi en-aut-mei=Kaya kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=KobayashiTatsuo C. en-aut-sei=Kobayashi en-aut-mei=Tatsuo C. kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=KoezukaRyo en-aut-sei=Koezuka en-aut-mei=Ryo kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=MiyakeAtsushi en-aut-sei=Miyake en-aut-mei=Atsushi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=GouchiJun en-aut-sei=Gouchi en-aut-mei=Jun kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=UwatokoYoshiya en-aut-sei=Uwatoko en-aut-mei=Yoshiya kn-aut-name= Yosh kn-aut-sei= Yosh kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=TokunagaMasashi en-aut-sei=Tokunaga en-aut-mei=Masashi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= affil-num=1 en-affil=Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=2 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=3 en-affil=Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=4 en-affil=The Institute for Solid State Physics, The University of Tokyo kn-affil= affil-num=5 en-affil=The Institute for Solid State Physics, The University of Tokyo kn-affil= affil-num=6 en-affil=The Institute for Solid State Physics, The University of Tokyo kn-affil= affil-num=7 en-affil=The Institute for Solid State Physics, The University of Tokyo kn-affil= affil-num=8 en-affil=The Institute for Solid State Physics, The University of Tokyo kn-affil= END start-ver=1.4 cd-journal=joma no-vol=9 cd-vols= no-issue= article-no= start-page=5376 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2019 dt-pub=2019329 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=Fermi level tuning of Ag-doped Bi2Se3 topological insulator en-subtitle= kn-subtitle= en-abstract= kn-abstract=The temperature dependence of the resistivity (rho) of Ag-doped Bi2Se3 (AgxBi2-xSe3) shows insulating behavior above 35 K, but below 35 K, rho suddenly decreases with decreasing temperature, in contrast to the metallic behavior for non-doped Bi2Se3 at 1.5-300 K. This significant change in transport properties from metallic behavior clearly shows that the Ag doping of Bi2Se3 can effectively tune the Fermi level downward. The Hall effect measurement shows that carrier is still electron in AgxBi2-xSe3 and the electron density changes with temperature to reasonably explain the transport properties. Furthermore, the positive gating of AgxBi2-xSe3 provides metallic behavior that is similar to that of non-doped Bi2Se3, indicating a successful upward tuning of the Fermi level. en-copyright= kn-copyright= en-aut-name=UesugiEri en-aut-sei=Uesugi en-aut-mei=Eri kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=UchiyamaTakaki en-aut-sei=Uchiyama en-aut-mei=Takaki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=GotoHidenori en-aut-sei=Goto en-aut-mei=Hidenori kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=OtaHiromi en-aut-sei=Ota en-aut-mei=Hiromi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=UenoTeppei en-aut-sei=Ueno en-aut-mei=Teppei kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= en-aut-name=FujiwaraHirokazu en-aut-sei=Fujiwara en-aut-mei=Hirokazu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=6 ORCID= en-aut-name=TerashimaKensei en-aut-sei=Terashima en-aut-mei=Kensei kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=7 ORCID= en-aut-name=YokoyaTakayoshi en-aut-sei=Yokoya en-aut-mei=Takayoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=8 ORCID= en-aut-name=MatsuiFumihiko en-aut-sei=Matsui en-aut-mei=Fumihiko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=9 ORCID= en-aut-name=AkimitsuJun en-aut-sei=Akimitsu en-aut-mei=Jun kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=10 ORCID= en-aut-name=KobayashiKaya en-aut-sei=Kobayashi en-aut-mei=Kaya kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=11 ORCID= en-aut-name=KubozonoYoshihiro en-aut-sei=Kubozono en-aut-mei=Yoshihiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=12 ORCID= affil-num=1 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=2 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=3 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=4 en-affil= Advanced Science Research Centre, Okayama University kn-affil= affil-num=5 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=6 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=7 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=8 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=9 en-affil=Graduate School of Materials Science, Nara Institute of Science and Technology kn-affil= affil-num=10 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=11 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= affil-num=12 en-affil=Research Institute for Interdisciplinary Science, Okayama University kn-affil= END