visual
visual

세미나

  • HOME
  • >
  • 소식
  • >
  • 세미나

KAIST Physics Distinguished Lecture

2015.07.14 10:44

admin 조회 수:8104

날짜 2015-07-16 16:00 
연사  
장소 E6-2, 1501 

[Lecture1] Multiferroic vortices: why & how do they form?

 

2015/7/16 (THU) 4PM, Lecture Hall, College of Natural Sciences (1501, E6-2) /자연과학대학 공동강의실

Sang-Wook Cheong

Director, Rutgers Center for Emergent Materials, Rutgers University

 

 

Hexagonal REMnO3 (RE= rare earths) with RE=Ho-Lu, Y, and Sc, is an improper ferroelectric where the size mismatch between RE and Mn induces a trimerization-type structural phase transition, and this structural transition leads to three structural domains, each of which can support two directions of ferroelectric polarization. Six different types of domains in h-REMnO3 meet in cloverleaf arrangements that cycle through all possible configurations, Occurring in pairs, the cloverleafs can be viewed as vortices and antivortices, in which the cycle of domain configurations is reversed. Vortices and antivortices are topological defects: even in a strong electric field they won’t annihilate. These ferroelectric vortices/antivortices are found to be associated with intriguing collective magnetism at domain walls, reflecting the multiferroic nature of vortices.

 

The formation of these multiferroic vortices turns out to be analogous to the formation of cosmic strings right after big bag and also the unbinding of vortex loops in superfluid transition. We will discuss the exact nature of this proliferation process of multiferroic vortices.

 

 

[Lecture2] Hybrid Improper Ferroelectrics: Z4xZ2 domains with Z3 vortices

 

2015/7/17 (FRI) 11AM, Lecture Hall, College of Natural Sciences (1501, E6-2) / 자연과학대학 공동강의실

Sang-Wook Cheong

Director, Rutgers Center for Emergent Materials, Rutgers University

 

 

Utilizing trilinear coupling of two types of octahedron rotations, hybrid improper ferroelectricity has been theoretically predicted in double layered compounds such as (Ca,Sr,Ba)3(Mn,Ti,Sn,Zr,Ge)2O7. On the other hand, there exists little theoretical prediction on practical properties of the potentially-ferroelectric compounds such as ferroelectric transition temperature, switchability of polarization, and chemical phase stability. We have attempted to fabricate single crystals of some of these compounds, and examined the physical properties of the crystals with the aim of discovering new bulk ferroelectrics with switchable polarization at room temperature. We will discuss the results of our comprehensive experimental investigation.

Ordering of charge/spin/orbital degrees of freedom in complex materials accompanies domains and domain walls associated with the directional variants (Zm) and also antiphases (Zn). In hybrid improper ferroelectric (Ca,Sr,Ba)3(Mn,Ti,Sn,Zr,Ge)2O7, four directional variants with different polarization directions can exist, and each polarization domain has two degenerate antiphases. It turns out that the hybrid improper ferroelectrics tend to exhibit a Z4xZ2 domain structure with Z3 vortices. This can be compared with the Z2xZ3 domain structure with Z6 vortices in hexagonal REMnO3.

 

 

Host: Department of Physics, KAIST
Contact: Prof. Chan-Ho Yang (Ext.2513)

번호 날짜 연사 제목
공지 2025-02-24 16:00    2025년 봄학기 콜로키움 안내
공지 2025-02-27 16:00    2025년 봄 물리학과 특별세미나 (광학/응집물리 분야)
615 2025-07-16 14:00  이준현 박사 (Staff Engineer, Samsung Research)  Scaling Laws and Transformers: Modern LLMs for the Physicist’s Mind file
614 2025-07-03 14:00  Dr. Young-Gwan Choi (Max Planck Institute )  Quantum sensing with NV centers: nanoscale magnetometry file
613 2025-06-26 16:00  Prof. Eun-Ah Kim (Cornell)  Attention to Quantum Complexity file
612 2025-06-05 11:00  Dr. Bruno Tomasello (University of Catania, Italy)  Crystal-Field Anisotropy and Low-Temperature Spin Seebeck in Terbium Iron Garnet file
611 2025-06-05 10:00  Dr . On Kim (University of Mississippi)  The Final Result from the Muon g-2 Experiment at Fermilab: The World’s Most Precise Measurement of the Muon Magnetic Anomaly file
610 2025-05-28 16:00  Dr. Thiago L. M. Guedes (Forschungszentrum Jülich)  Computing the graph-changing dynamics of loop quantum gravity file
609 2025-05-26 16:00  윤석호 박사(삼성종합기술원)  Photonics in the Age of AI: Industry Trends and Perspectives file
608 2025-05-23 11:00  천상모 교수(한양대학교)  Superconductivity in Topological Materials file
607 2025-05-22 16:00  유현승 박사(삼성종합기술원)  Reconstructing Reality: Learning-based Methods for 3D Imaging and Graphics file
606 2025-05-22 14:30  Prof. Keun Su Kim (The Univ. of Yonsei)  Sublattice-interference model for Fermi arcs in cuprates file
605 2025-05-15 16:00  노찬 박사(KAIST)  Generation of multimode Gaussian quantum states and their applications for quantum computing file
604 2025-05-13 16:00  Mr. Heonjoon Park(Univ. Washington, USA)  Fractional Quantum Anomalous Hall Effect file
603 2025-05-02 11:00  Prof. Joonho Jang  Anderson localization of electrons in a moire-of-moire lattice of helical twisted trilayer graphene file
602 2025-05-01 16:00  Dr. Inwook Kim (Lawrence Livermore National Laboratory)  BSM Physics Search with Quantum Sensors file
601 2025-04-29 16:00  Dr. Tokuro Shimokawa (Okinawa Institute of Science and Technology)  Can experimentally-accessible measures of entanglement distinguish quantum spin liquid and random singlet phases? file
600 2025-04-29 10:00  Dr. Yeonju Go (Brookhaven National Laboratory)  Exploring the Hottest Matter in the Universe: Quark-Gluon Plasma through Hard Probes and Artificial Intelligence file
599 2025-04-28 16:00  지명국 (연세대 천문우주학과)  Galaxy Cluster Collisions as Cosmic Laboratories for Dark Matter file
598 2025-04-22 16:00  Dr. Nanse Esaki (The University of Tokyo)  Spin Nernst and thermal Hall effects of topological triplons in quantum dimer magnets on the maple-leaf and star lattices file
597 2025-04-22 13:30  Dr. Chaebin Kim (Georgia Institute of Technology)  Emulation of quantum correlations by classical dynamics in quantum magnets file
596 2025-04-21 16:00  Prof. Ambrose Sungseok Seo (Univ of Kentucky)  Condensed matter physics? All you gotta do is just meet me at the ... file