臺灣大學凝態中心研究員周方正 - 國科會物理研究推動中心

NSC Taiwan Consortium of Emergent Crystalline Materials!1

Theory PredictioninterpretationScience Material SingleCrystalCondensedMatterSciences Measurement Extremeconditions Technology SingleCrystalGrowth Art LatticeSpinStrongCouplingOrbitalCharge3

!!X• (Bi 2 Se 3 )• (Bi 2 Te 3 Na x CoO 2 )• (Li x CoO 2 LiFePO 4 )• • • • !!5!

Superconductor and thermoelectric material: Na x CoO 2• superconducting phase Fermi surface (PRL2006)• clarified Na ion diffusion problem (PRB2007)• discovery of new ordering phases (PRB2007,2008)• proposed Na ordering patterns (PRL2008)• New phase diagram proposed (PRB2009)• impact on physical properties (PRL2007,2008,2009, 2011)Multiferroics and low dimensional magnetism: LiCu 2 O 2!"#%&'-. /0-. 10ca4 1$&(")*+ , $&(")*+ $• Li nonstoichiometry identified (PRB2008)• novel spin dimerization phenomenon found (PRB2009)• complete phase diagram mapped (PRB2010)6

• Bi 2 Se 3 : topological Insulator defect chemistry• Cu x Bi 2 Se 3 : superconductivity and TI• Mn x Bi 2 Se 3 : ferromagnetism• C x Bi 2 Se 3 : novel staging and thermoelectricity• Na x CoO 2 : spin entropy contribution to TE• Li x CoO 2 & Li x NiO 2 : phase diagram• LiFePO 4 : surface vs. bulk magnetism• Bi 2 Sr 2 Co 2 O y : Pb hole doping and TE• SCFZ phase diagram: binary for crystal growth• TiOBr: spin Peierls spin dimerization• Ba-Cu-Te-Sb-O: novel frustrated trimer & kagome• BiOCuSe: non-FeAs CuS layered system• Cu x TiSe 2 and Misfit series: CDW & superconductivity• MnSi: skyrmion and defect• Sr 2 CuO 3+δ : GPa phase revisited7

major advanced equipmentGPa ultrahigh pressure furnaceSQUID-VSMOptical floating-zone furnaceSingle crystal scanning X-rayEPMA?yesRF furnace8

Material synthesis under ultrahigh pressure• 1GPa=10000 atm• 3km deep ~ 1000 atm• 0.01-1 eV è 1GPa-1TPa10

FEI Tecnai-F20@200kV:Monochromator and (S)TEMJEOL JEM-2100F@200kV:Cs-STEMEDXCscorrectorEDXEELSEELS

STEM-EDX Chemical MappingCrystal Structure: GaAsSTEM-EDX5.88 ÅAsGabcrystalX-ray (solid angle:4π sr.)EDXacsolid angle:0.13 sr.[110]-projected GaAsAs Ga1.47 ÅDumbbellstructureDOSE FX-rayb~1% X-ray collected;EDX detector withgood statistics needed!M.-W. Chu et al., Phys. Rev. Lett. 104, 196101 (2010); 2011

Single Atomic-Column EELS in Emergent MaterialsDOSE FF.-K. Chiang, M.-W. Chu et al., Phys. Rev. B 83, 245105 (2011)

Na x CoO 2Li x CoO 2 LiCu 2 O 2 TaSe 2TaS 2Cu x TaS 2Sr 2 CuO 2 Cl 2 Sr 2 Cu 3 O 4 Cl 2 LiFePO 4 SrFeO 3Cu 2 OCl 2 La 5 Ca 9 Cu 24 O 41MnSi CaCu 2 O 3La 2 CuO 4La 2-x Sr x CuO 4 Pr 2 CuO 4(Fe 0.95 Al 0.05 ) 2 O 3 LiFeAs DyMnO 3Fe 1+x Te CuFeO 2 CuCrO 2 Bi 2 Se 3 BiCu 2 PO 614

Collaboration and TrainingCollaboration styles:• Provide well characterized crystals• Help to grow specific crystals• Student/postdoc on-site training 辦 1) 步 2) ,,3) 4) 5) 6) 15