visual
visual

세미나

  • HOME
  • >
  • 소식
  • >
  • 세미나

KAIST Physics Distinguished Lecture

2015.07.14 10:44

admin 조회 수:2257

날짜 2015-07-16 16:00 
일시 2015/07/16-07/17 
장소 E6-2, 1501 
연사 Sang-Wook Cheong (Rutgers Univ.) 

[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 장소 제목
공지 2022-10-24 16:00  E6 #1501(공동강의실)  Physics Colloquim(Fall 2022)
공지 2022-09-21 10:30  E6-1 #1501  [Update 세미나 영상] Distinguished Lecture 'The Magic of Moiré Quantum Matter' Prof. Pablo Jarillo-Herrero(Department of Physics, MIT)
공지 2022-11-11 11:00  E6-2 #1323  [Update 세미나영상] (응집물리 세미나) Honeycomb oxide heterostructures for quantum spin liquid
공지 2022-10-28 11:00  E6-2 #1323  [Update 세미나영상] (응집물리 세미나) Machine-Learning-Guided Prediction models and Materials discovery for high Tc cuprates
공지 2022-10-07 11:00  E6-2 #1323  [Update 세미나 영상] (응집물리 세미나) Competing orders in a vanadium-based kagome metal monolayer
공지 2022-09-23 11:00  E6-2 #1323  [Update 세미나 영상] (응집물리 세미나) Steady Floquet-Andreev states in graphene Josephson junctions
공지 2022-09-22 11:00  E6-1 #1323  2022 가을학기 응집물리 및 광학 세미나 전체 일정
214 2022-09-15 13:00  E6-2, #1323  AdS black holes: a review
213 2016-11-18 10:30  #5318(5th fl.)  Non-equilibrium many-body spin dynamics in diamond
212 2016-10-27 16:00  #1323(E6-2)  Terahertz Metal Optics
211 2019-06-28 13:30  #1323, E6-2  Magnetic domains and domain wall conduction in pyrochlore iridate thin films and heterostructures file
210 2016-04-08 13:30  E6-2. 1st fl. #1501  Theoretical Overview of Iron-based superconductors and its future
209 2017-09-26 11:00  #1323 (E6-2. 1st fl.)  Time-resolved ARPES study of Dirac and topological materials
208 2019-11-01 14:30  E6-2. 1st fl. #1323  Squeezing the best out of 2D materials file
207 2019-04-19 14:30  E6-2. 1st fl. #1323  A family of finite-temperature electronic phase transitions in graphene multilayers file
206 2015-11-06 16:30  E6-2, #5318  Topological Dirac line nodes in centrosymmetric semimetals
205 2018-03-16 16:00  E6-2. 1st fl. #1323  Van der Waals Heterostructures from Quantum Transport to Ultrafast Optoelectronics file
204 2018-03-16 16:00  E6-2. 1st fl. #1323  Van der Waals Heterostructures from Quantum Transport to Ultrafast Optoelectronics file
203 2022-08-09 14:00  KI building (E4), Lecture Room Red (B501)  Quantum biology in fluorescent protein: a new model system to study quantum effects in biology file
202 2016-05-13 13:30  E6. #1501(1st fl.)  Aperiodic crystals in low dimensions
201 2018-04-11 16:00  #1323 (E6-2, 1st fl.)  Non-Gaussian states of multimode light generated via hybrid quantum information processing file
200 2017-05-12 13:30  E6-2. 1st fl. #1323  Topological Dirac insulator
199 2022-05-13 16:00  자연과학동(E6-2) 1st fl. #1323  High-fidelity iToffoli gate for fixed-frequency superconducting qubits file
198 2022-06-10 11:00  Online seminar  Record-quality two-dimensional electron systems file
197 2018-04-11 13:30  #1323 (E6-2, 1st fl.)  Probing 3D Structure and Physical Properties of Materials at the Single-Atom Level file
196 2018-10-15 16:00  #1323, E6-2  Universal properties of macroscopic current-carrying systems file
195 2016-09-02 16:00  E6-2(1st fl) #1323  Quantum Electrical Transport in Topological Insulator Nanowires