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Quantum Matter Research under Extreme Physical Conditions Outlook for 2006-2007 in Korea Kee Hoon Kim School of Physics and Astronomy & Center for Strongly Correlated Material Research eXtreme Multifunctional Physics Laboratory (XMPL), Seoul National University, South Korea Sep. 27, 2006

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Post-doc: Peter Mann Deepshikha Jaiswal Raj Sankar Ph D candidates: Yoon Seok Oh Jae Wook Kim So-Young Haam MS students: Sewhan Chun, Ingyu Kim Peter Littlewood (Theory) Christoph Bergemann (Exp.) Peter Mann S. S. Saxena Stephen Rowley G. G. Lonzarich SNU (XMPL) Kee Hoon Kim (Exp.) Quantum Matter Group (Cavendish Lab.)

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Quantum Criticality Proposed to Instigate New Phases Including Exotic Superconductivity R. B. Laughlin et al., Adv. Phys. 50, 361 (2001). AFM AFI Pseudogap FL SC FL = res +AT 2 1: fluctuations (e.g. spin fluctuations) present at T = 0 can mediate quasiparticle pairing 2: singular density of states (i.e. m* ) is unstable. Superconductivity very efficient at opening gap and lowering energy Reasons: Non-Fermi Liquids Fundamental questions: can we understand new states of matter including exotic orders like high Tc superconductivity?

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Exploring correlated electron system under extreme physical conditions Quantum Matter Research Agenda SNU (XMPL) Cavendish Quantum Matter Group Superconducting B up to 21 T Dilution Fridge 5 mK Anvil cell: 150 kbar Clamp cell: 30 kbar Cavendish Correlated Electron Theory Group P B, T

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Tools I: Quantum Matter Growth + Crystallography (x) Optical Floating Zone Furnace +Flux Growth Technique (Quantum) Multiferroics RMnO 3 … Highly frustrated quantum spin system A new correlated Fermion system Pt crucible Polarized Microscope Real time Laue analyses GaFeO 3 TbMn 2 O 5

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Tools II: Measurements under High Field up to 100 T (B) All plastic and silicon; no eddy current !! Phase-sensitive Synchronous Detection Synchronous Clock (n x f ) Dual Synthesizer Digitizer Drive ( f ) Signal 60 T calorimeter 100kHz ac tools 33 T Nanocalorimeter

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Outstanding problems to be answered How the phases can be formed near the QCP of a correlated matter? Is the new phase really linked to the QCP? A QCP can involve the large FS reconstruction? Fermiology vs Hall effects

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K. H. Kim et al. PRL 93, 126404 (2004); K. H. Kim PRL 2003

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Rh 4 % Rh 0 % Research Highlight : Hall studies of U(Ru 1-x Rh x ) 2 Si 2 A jump in carrier number ( n ~1 el/U) across phase II suggests the FS reconstruction to induce a discontinuous Fermi surface volume change. Results of pulsed field explorations dHv study at Cavendish lab. is most valuable to this problem R H = xy /B =-1/ne Y. S. Oh et al. submitted to PRL

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SpinOrbital Charge Multifunctional Multiferroic materials Magnetic control Electric control Lattice/photonic control Quantum Magnetism-Ferroelectricity Coupling in Multiferroics GaFeO 3 TbMn 2 O 5 Next generation memory materials with more control ability APS Focus Session 2003 년 1 2004 년 1 2005 년 2 2006 년 4 New material search + highly senstive measurements tools: 2003-2006 Nature 5 Nature materials 6 Science 7 PRL 22 Very hot emerging research area New multiferroics? ; Fundamental coupling mechanism?; Needs for multiphase space exp. ?

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electric polarization dielectric constant PE hysteresis loop Magnetic birefringence Magnetoelectric susceptibility (film and low T study ready TbMn 2 O 5 Multiferroic Xtals S. Y. Haam et al., to submitted to PRL Electric polarization map of a multiferroic under high magnetic fields New high field phase transition Quantum Paraelectric Matter Understanding of electric polarization generation 9T : PPMS 45T: mid-pulse 60T: short-pulse 100T: short-pulse 45T: static field RMn 2 O 5, RMnO 3, RCrO 3 Nano-Pillar Composite PZT:CoNi 2 Fe 4 Research Highlight : B-T phase diagram of multiferroics

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ε(T) of BiMn 2 O 5 at constant magnetic field Careful T sweep of dielectric constant near B c down to 0.6 K Very similar to the well-known quantum paraelectric behavior of SrTiO 3 Can be a new quantum paraelectric achieved with magnetic field tuning? J. W. Kim et al. to be submitted A sign of quantum ferreoelectrics

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Outstanding problems to be investigated 1. Can we find a new quantum paraelectrics near the quantum critical point of ferroelectrics or multiferroics? BiMn 2 O 5 case 2. Can we realize new multiferroics ? (eg. SnTe doped with Mn?) Theory + Experiments (Design of materials) 3. Developments of quantum technology to explore challenging measurements Tiny magnetic moment measurement as tuned by electric fields Tiny specific heat measurements under quantum regime to see electronic quantum oscillations or to study phase transition at low T

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Recently discovered superconducting below 50mK, Ag 5 Pb 2 O 6 has a very simple Fermi surface with m * /m~1. Sutherland et al, PRL 96, 097008 (2006) Mann et al, Physica C, M2S Proc. (2006) However, the resistivity is not simple. It has quasi-T 2 dependence up to at least room temperature. What is the cause? Phonons? Yonezawa and Maeno, PRB 70, 184523 (2004) It will be useful to measure C more precisely up to and beyond 400K using the high T heat capacity probe, to confirm saturation to Dulong-Petit value. Plus we need more theory input…! Peter Mann Research plan, Ag 5 Pb 2 O 6 : a simple superconductor?

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Research plan : Electric Field Induced Magnetic Moment Electric field induced magnetization study E-torque magnetometer developments and measurements for multiferroic thin film devices and crystals E-VSM developments and study Magnetoelectric susceptibility measurements for films at low temperatures Study on new multiferroic materials and their nanostructure Search for materials showing magnetic moment variation actuated by electric fields Developments of magnetoelectric device with naopillar and multilayer forms Ba-Hexaferrite, Y 3 Fe 5 O 12, GaFeO 3 Multiferroic crystal & filmFab. of highly senstive-measurement tool Torque magnetometer Ni 3 B 7 O 12 I Switching of P (E~1000V/cm) by 180 deg. with a rotation of M (H~0.1 T) by 90 deg. Z x y P MsMs

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英 Cambridge Univ. 韓 SNU 1 st year 2nd 3rd Quantum Matter & Quantum Phase Transition Quantum Matter Theory + High B & High B Next generation measurement tools + Search for a New groundstates of quantum matter Understanding quantum criticality and phase formation Measurements under extreme limit Quantum Matter Search, Growth, and Characterization Pressure cell development (4GPa) Nano-calorimeter technique Striction cell fabrications ~10 mK ultralow temperature High pressure measurements Torque magnetometer Ultralow temp.(mK) calorimetry Future Research Strategy Nanocalorimetry QPT study We’re looking forward to being part of the CKC family!

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