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SUMMARY:Strain Engineering of Flexo-Phonons and Flexo-Ferrons in Thin Film
 s of Van der Waals Ferrielectrics
DTSTART;VALUE=DATE-TIME:20260922T134000Z
DTEND;VALUE=DATE-TIME:20260922T134500Z
DTSTAMP;VALUE=DATE-TIME:20260914T013231Z
UID:indico-contribution-521@indico.bitp.kiev.ua
DESCRIPTION:Speakers: Eugene Eliseev (Frantsevich Institute for Problems i
 n Materials Science\, National Academy of Sciences of Ukraine)\nIt was sho
 wn earlier that size effect of soft phonon dispersion is principally impor
 tant in nanosized ferroics [1]. Also\, the size and strain effects can det
 ermine the anomalous polarization reversal in strained thin films of van d
 er Waals ferrielectrics [2]. It has been shown recently that the influence
  of the flexoelectric coupling (shortly “flexocoupling”) on the fluctu
 ations of electric polarization and elastic strains can lead to the princi
 pal changes of the dispersion law of soft optical and acoustic phonons (sh
 ortly “flexophonons”) and ferrons (shortly “flexoferrons”) in a bu
 lk van der Waals ferrielectrics [3]. At that applied electric field influe
 nces strongly on the anisotropic dispersion of the flexocoupling induced p
 honons and ferrons in van der Waals ferrielectrics [4]. A strong coherent 
 ferrons and cavity acoustic phonons is predicted in the of van der Waals f
 errielectric $CuInP_2 S_6$ [5].\nUsing the Landau-Ginzburg-Devonshire appr
 oach\, in this work we reveal that the dispersion of flexophonons and flex
 oferrons is strongly dependent on the sign and magnitude of elastic strain
 s originated from the lattice constants mismatch in thin strained films of
  van der Waals ferrielectric $CuInP_2 S_6$. In particular\, the frequency 
 of acoustic flexophonons and flexoferrons tends to zero at nonzero wavevec
 tors $k>k_{cr}$\, where the critical value of the wavevector $k_{cr}$ is d
 etermined by the mismatch strain and flexocoupling strength. Zeroing of th
 e flexophonon frequency\, that appears with increase of tensile strains\, 
 indicates a possible emergence of a spatially modulated incommensurate pol
 ar phase induced by the flexo-strain effects. Analytical results\, derived
  in this work\, open the way for strain engineering of flexophonon and fle
 xoferron dispersion in thin films of van der Waals ferrielectrics.\nAcknow
 ledgements. The work is primary supported as part of the Computational Mat
 erials Sciences Program funded by the US Department of Energy\, Office of 
 Science\, Basic Energy Sciences\, under Award Number DE-SC0020145. The par
 t of A.N.M. and E.A.E. efforts are also supported by National Academy of S
 ciences of Ukraine (grants No. 5.8/26-П\, 1.4.B/222\, III-6-26). \nRefere
 nces\n1. A. N. Morozovska\, and E. A. Eliseev. Size effect of soft phonon 
 dispersion law in nanosized ferroics. Phys.Rev. B\, 99\, 115412 (2019)\; h
 ttps://link.aps.org/doi/10.1103/PhysRevB.99.115412\n2. A. N. Morozovska\, 
 E. A. Eliseev\, A. Ghosh\, M. E. Yelisieiev\, Y. M. Vysochanskii\, and S. 
 V. Kalinin. Anomalous Polarization Reversal in Strained Thin Films of CuIn
 P2S6\, Phys. Rev. B\, 108\, 054107 (2023)\; https://link.aps.org/doi/10.11
 03/PhysRevB.108.054107\n3. A. N. Morozovska\, E. A. Eliseev\, O. V. Berezn
 ikov\, M. Ye. Yelisieiev\, G.-D. Zhao\, Y. Zhu\, V. Gopalan\, L.-Q. Chen\,
  J.-M. Hu\, and Y. M. Vysochanskii\, Flexo-coupling induced phonons and fe
 rrons in Van der Waals ferroelectrics\, Physical Review B 112\, 014110 (20
 25)\; https://doi.org/10.1103/mr9v-khtj\n4. A. N. Morozovska\, E. A. Elise
 ev\, Y. Zhu\, Y. M. Vysochanskii\, V. Gopalan\, L.-Q. Chen\, and J.-M. Hu\
 , The Influence of Electric Field on the Anisotropic Dispersion of the Fle
 xocoupling Induced Phonons and Ferrons in Van der Waals Ferrielectrics. Jo
 urnal of Applied Physics\, 138\, 134101 (2025)\; https://doi.org/10.1063/5
 .0294057\n5. Y. Zhu\, Ji. Wu\, A. N. Morozovska\, E. A. Eliseev\, Y. M. Vy
 sochanskii\, V. Gopalan\, L.-Q. Chen\, X. Zhang\, W. Zhang\, J.-M. Hu. Str
 ong coupling between coherent ferrons and cavity acoustic phonons. Physica
 l Review Applied (2026)\; https://doi.org/10.1103/q9np-lk7y\n\nhttps://ind
 ico.bitp.kiev.ua/event/18/contributions/521/
LOCATION:Bogolyubov Institute for Theoretical Physics Conference Hall
URL:https://indico.bitp.kiev.ua/event/18/contributions/521/
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