Artificial two-dimensional polar metal at room temperature

Yanwei Cao; Zhen Wang; Se Young Park; Yakun Yuan; Xiaoran Liu; Sergey M Nikitin; Hirofumi Akamatsu; M Kareev; S Middey; D Meyers; P Thompson; P J Ryan; Padraic Shafer; A N'Diaye; E Arenholz; Venkatraman Gopalan; Yimei Zhu; Karin M Rabe; J Chakhalian

doi:10.1038/s41467-018-03964-9

Artificial two-dimensional polar metal at room temperature

Nat Commun. 2018 Apr 18;9(1):1547. doi: 10.1038/s41467-018-03964-9.

Authors

Yanwei Cao^{1

2}, Zhen Wang^{3

4}, Se Young Park⁵, Yakun Yuan⁶, Xiaoran Liu⁷, Sergey M Nikitin⁶, Hirofumi Akamatsu⁶, M Kareev⁷, S Middey^{8

9}, D Meyers⁴, P Thompson¹⁰, P J Ryan^{11

12}, Padraic Shafer¹³, A N'Diaye¹³, E Arenholz¹³, Venkatraman Gopalan⁶, Yimei Zhu⁴, Karin M Rabe⁷, J Chakhalian⁷

Affiliations

¹ Department of Physics and Astronomy, Rutgers University, Piscataway, NJ, 08854, USA. yc874@physics.rutgers.edu.
² CAS Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Zhejiang, 315201, Ningbo, China. yc874@physics.rutgers.edu.
³ Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA, 70803, USA.
⁴ Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY, 11973, USA.
⁵ Department of Physics, University of California Berkeley, Berkeley, CA, 94720, USA.
⁶ Department of Materials Science and Engineering and Materials Research Institute, Pennsylvania State University, University Park, PA, 16802, USA.
⁷ Department of Physics and Astronomy, Rutgers University, Piscataway, NJ, 08854, USA.
⁸ Department of Physics, University of Arkansas, Fayetteville, AR, 72701, USA.
⁹ Department of Physics, Indian Institute of Science, Bangalore, 560012, India.
¹⁰ XMas CRG, European Synchrotron Radiation Facility, Cedex 38043, Grenoble, France.
¹¹ Advanced Photon Source, Argonne National Laboratory, Argonne, IL, 60439, USA.
¹² School of Physical Sciences, Dublin City University, Dublin, 9, Ireland.
¹³ Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.

Abstract

Polar metals, commonly defined by the coexistence of polar crystal structure and metallicity, are thought to be scarce because the long-range electrostatic fields favoring the polar structure are expected to be fully screened by the conduction electrons of a metal. Moreover, reducing from three to two dimensions, it remains an open question whether a polar metal can exist. Here we report on the realization of a room temperature two-dimensional polar metal of the B-site type in tri-color (tri-layer) superlattices BaTiO₃/SrTiO₃/LaTiO₃. A combination of atomic resolution scanning transmission electron microscopy with electron energy-loss spectroscopy, optical second harmonic generation, electrical transport, and first-principles calculations have revealed the microscopic mechanisms of periodic electric polarization, charge distribution, and orbital symmetry. Our results provide a route to creating all-oxide artificial non-centrosymmetric quasi-two-dimensional metals with exotic quantum states including coexisting ferroelectric, ferromagnetic, and superconducting phases.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.
Research Support, Non-U.S. Gov't