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SUMMARY:Manifestation of bilinear flexo-antiferrodistortive coupling at tw
 ins and antiphase boundaries in ferroelastics
DTSTART;VALUE=DATE-TIME:20260924T123000Z
DTEND;VALUE=DATE-TIME:20260924T130000Z
DTSTAMP;VALUE=DATE-TIME:20260914T040700Z
UID:indico-contribution-512@indico.bitp.kiev.ua
DESCRIPTION:Speakers: Anna Morozovska (Інститут фізики НА
 Н України)\nThe flexoelectric-type coupling between the gradients 
 of electric polarization\, described by a true polar vector $\\vec{P}$\, a
 nd the antiphase rotation of structural groups\, described by an axial pse
 udovector $\\vec{\\Phi }$\, can lead to the appearance of interfacial pola
 rization at the twin walls\, antiphase boundaries and surfaces of antiferr
 odistortive (AFD) ferroelastics [1]. The linear-quadratic flexo-AFD coupli
 ng may contribute significantly to observable interfacial polarization ind
 uced by oxygen octahedral rotations at the antiphase boundaries and/or twi
 n walls in YMnO3\, Ca3Mn2O7\, CaTiO3 and SrTiO3\, as well as lead to the a
 ppearance of versatile spatially modulated structures in multiferroics [1]
 .\nThe quadratic dependence of the linear-quadratic flexo-AFD coupling ene
 rgy on $\\vec{\\Phi}$ appeared principally important for the emergence of 
 interfacial polarization\, because the odd powers of anti-phase (i.e.\, si
 gn-alternating in neighboring sublattices) pseudovector $\\vec{\\Phi }$ ca
 nnot induce the continuous polarization of structural domain walls\, surfa
 ces or interfaces in AFD ferroelastics. Therefore\, it seemed that it made
  little sense to consider odd powers of $\\vec{\\Phi }$ when constructing 
 the sublattice-insensitive flexo-AFD coupling energy. However\, recently V
 isser et al. [2] and Fang et al. [3] proposed the concept of alterelectric
 ity\, an electrical analogue of altermagnetism\, in which two switchable s
 tates possess alternating band structures. \nUsing the Landau-Ginsburg-Dev
 onshire approach we show that the linear gradient-type coupling between th
 e electric polarization vector $\\vec{P}$ and antiferrodistortive long-ran
 ge order parameter pseudovector $\\vec{\\Phi }$\, that has the form of Lif
 shitz invariant $\\left(\\vec{P}\\bullet \\mathrm{\\nabla }\\times \\vec{\
 \Phi }\\\; -\\vec{\\Phi }\\bullet \\mathrm{\\nabla }\\times \\vec{P}\\righ
 t)/2$ and named “bilinear flexo-antiferrodistortive coupling”\, can em
 erge in all antiferrodistortive ferroelastics\, since it is symmetry-allow
 ed [4]. Using the four sublattices model we reveal that the bilinear flexo
 -antiferrodistortive coupling can induce the sublattice-sensitive polariza
 tion at the twin walls and antiphase boundaries in antiferrodistortive fer
 roelastics without any ferroelectric or antiferroelectric ordering. Since 
 the induced polarization $\\vec{\\delta P}$ is perpendicular to $\\vec{\\P
 hi}$ and counter-directed in neighboring sublattices with checkerboard-typ
 e direction of $\\vec{\\Phi}$\, such structure of $\\vec{\\delta P}$ may c
 orrespond to the alterelectric-type quadrupolar electric order. However\, 
 physical manifestations of the bilinear flexo-antiferrodistortive coupling
  are invisible in most nanostructured antiferrodistortive ferroelectrics a
 nd antiferroelectrics due to the domination of piezoelectric and/or omnipr
 esent linear flexoelectric couplings. We have shown that the bilinear flex
 o-antiferrodistortive coupling can induce alterelectric-type polarization 
 near antiferrodistortive domain boundaries in ferroelastics without any fe
 rroelectric or antiferroelectric long-range ordering [1].\nAcknowledgement
 s. The work is primary supported as part of the Computational Materials Sc
 iences Program funded by the US Department of Energy\, Office of Science\,
  Basic Energy Sciences\, under Award Number DE-SC0020145. The part of A.N.
 M. and E.A.E. efforts is also supported by National Academy of Sciences of
  Ukraine (grants No. 5.8/26-П\, 1.4.B/222\, III-6-26). \n[1]. A.N. Morozo
 vska\, E.A. Eliseev\, M.D. Glinchuk\, L.-Q. Chen\, V. Gopalan. Interfacial
  Polarization and Pyroelectricity in Antiferrodistortive Structures Induce
 d by a Flexoelectric Effect and Rotostriction. Phys.Rev. B. 85\, 094107 (2
 012)\; https://doi.org/10.1103/PhysRevB.85.094107\n[2]. A. Visser\, V. Kö
 nye\, O. Janson\, J. van den Brink\, C. Coulais\, and J. van Wezel. "Multi
 polar Piezoelectricity and Anisotropic Surface Transport in Alterelectrics
 ." arXiv preprint arXiv:2604.18324 (2026)\; https://doi.org/10.48550/arXiv
 .2604.18324\n[3]. S. Fang\, J. Wang\, Z. Guo\, J. Gong\, H. Meng\, W. Wang
 \, Z. Cheng\, X. Wang\, and Y. S. Ang. "Alterelectricity: Electrical Analo
 gue of Altermagnetism." arXiv preprint arXiv:2604.07112 (2026)\; https://d
 oi.org/10.48550/arXiv.2604.07112\n[4]. E. A. Eliseev\, A. N. Morozovska\, 
 A. Saha and V. Gopalan. Bilinear Flexo-Antiferrodistortive Coupling in Fer
 roelastics: Polar Twins\, Antiphase Boundaries and Fingerprints of Alterel
 ectricity. ArXiv Preprint (2026)\; https://doi.org/10.48550/arXiv.2606.294
 56\n\nhttps://indico.bitp.kiev.ua/event/18/contributions/512/
LOCATION:Bogolyubov Institute for Theoretical Physics Conference Hall
URL:https://indico.bitp.kiev.ua/event/18/contributions/512/
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