세미나안내

[2016 11 09] 정기세미나 7th

Polar Metals by Geometric Design

MSE Graduate Students and Researchers

관리자 | 2016.11.07 09:18 | 조회 529


 Date: 2016. 11. 09(WED) , 17:00 ~ 18:15

 Place: Science Building, Room.202 Multimedia Room

 Title: Polar Metals by Geometric Design

 Speaker: Prof. Chang-Beom Eom(Univ. Wisconsin-Madison)

Host of a Seminar: Prof. Jong Kyu Kim

 

Speaker Language: ENGLISH

 

Abstract:

 

Gauss’s law dictates that the net electric field inside a conductor in electrostatic equilibrium is zero by effective charge screening; free carriers within a metal eliminate internal dipoles that may arise owing to asymmetric charge distributions. Quantum physics supports this view, demonstrating that delocalized electrons make a static macroscopic polarization, an ill-defined quantity in metals—it is exceedingly unusual to find a polar metal that exhibits long-range ordered dipoles owing to cooperative atomic displacements aligned from dipolar interactions as in insulating phases. Here we describe the quantum mechanical design and experimental realization of room-temperature polar metals in thinfilm ANiO3 perovskite nickelates using a strategy based on atomicscale control of inversion-preserving (centric) displacements. We predict with ab initio calculations that cooperative polar A cation displacements are geometrically stabilized with a nonequilibrium amplitude and tilt pattern of the corner-connected NiO6 octahedra—the structural signatures of perovskites—owing to geometric constraints imposed by the underlying substrate. Heteroepitaxial thin-films grown on LaAlO3 (111) substrates. Heteroepitaxial thin-films grown on LaAlO3 (111) substrates fulfil the design principles. We achieve both a conducting polar monoclinic oxide that is inaccessible in compositionally identical films grown on (001) substrates, and observe a hidden, previously unreported, non-equilibrium structure in thin-film geometries [1]. We expect that the geometric stabilization approach will provide novel avenues for realizing new multifunctional materials with unusual coexisting properties.

This work has been done in collaboration with T. H. Kim, D. Puggioni, Y. Yuan, L. Xie, H. Zhou, N. Campbell, P. J. Ryan, Y. Choi, J.-W. Kim, J. R. Patzner, S. Ryu, J. P. Podkaminer, J. Irwin, Y. Ma, C. J. Fennie, M. S. Rzchowski, X. Q. Pan, V. Gopalan, J. M. Rondinelli.

[1] T. H. Kim, et al., Nature. 533, 68 (2016)

 

 

 

Department of Materials Science and Engineering

 


30POSTECH



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