• Open Access

Polarity reversal of the charge carrier in tetragonal TiHx(x=1.62.0) at low temperatures

Ryota Shimizu, Yuki Sasahara, Ikutaro Hamada, Hiroyuki Oguchi, Shohei Ogura, Tetsuroh Shirasawa, Miho Kitamura, Koji Horiba, Hiroshi Kumigashira, Shin-ichi Orimo, Katsuyuki Fukutani, and Taro Hitosugi
Phys. Rev. Research 2, 033467 – Published 22 September 2020

Abstract

We present a combined experimental and theoretical study of the charge transport properties of TiHx(x=1.62.0) epitaxial thin films. We found that the Hall coefficient of TiHx strongly depends on hydrogen content and unit-cell volume: Nearly stoichiometric TiHx(x2.0) films with large unit-cell volumes showed positive Hall coefficients at 4 K, whereas TiHx samples with x<1.7 and small unit-cell volumes showed negative Hall coefficients at 4 K. Our density functional theory calculations reveal that the volume change leads to the change in the aspect ratio of the tetragonal lattice, thereby lifting the degeneracy of Ti t2g states, and alters the contributions of electrons and holes at the Fermi surface and the sign of the Hall coefficient. The present study clarifies the important role of the lattice symmetry in determining the charge carrier polarity, and we suggest that electronic properties of metal hydrides can be tuned by the lattice parameters via the hydrogen contents.

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  • Received 3 September 2019
  • Accepted 7 August 2020

DOI:https://doi.org/10.1103/PhysRevResearch.2.033467

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Ryota Shimizu1,2,*, Yuki Sasahara1, Ikutaro Hamada3, Hiroyuki Oguchi4, Shohei Ogura5, Tetsuroh Shirasawa6, Miho Kitamura7, Koji Horiba7, Hiroshi Kumigashira7,8, Shin-ichi Orimo4,9, Katsuyuki Fukutani5,10, and Taro Hitosugi1

  • 1School of Materials and Chemical Technology, Tokyo Institute of Technology, Meguro, 152-8552, Japan
  • 2PRESTO, Japan Science and Technology Agency, Kawaguchi, 332-0012, Japan
  • 3Department of Precision Science and Technology, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
  • 4Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
  • 5Institute of Industrial Science, The University of Tokyo, Meguro, 153-8505, Japan
  • 6National Institute of Advanced Industrial Science and Technology, Tsukuba, 305-8560, Japan
  • 7Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan
  • 8Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, 980-8577, Japan
  • 9Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan
  • 10Advanced Science Research Center, Japan Atomic Energy Agency (JAEA), 2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195, Japan

  • *shimizu.r.af@m.titech.ac.jp

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Vol. 2, Iss. 3 — September - November 2020

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