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SDW Induced Charge Stripe Structure in FeTe Department of Applied Physics, Hokkaido University Y. Kawashima, K.Ichimura, J. Ishioka, K. Yamaya, S. Tanda Department of Physics, Hokkaido University T. Kurosawa, M. Oda

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Stripe Structure Usually occur with anisotropic interaction Long range attractive interaction Short range repulsive interaction Ex)Dipole-Dipole interaction

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W. F. Wang et. al. New J. Phys. 11 045003(2009) Iron-based Superconductors LaFePO(1111) Fe-P La-O Coexistence of magnetism and superconductivity New Type Strong correlated system

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Magnets and Iron-based Superconductors Magnet Iron-based Superconductor ex)Fe, Ni, Coex)LaFePO,BaFe 2 As 2 Main Character Spin Main Character Charge Spin-Spin Interaction StrongWeak New Phase? Spin and Charge Spin Density Wave(SDW) Investigate the new electronic state Our Purpose spin

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FeTe Investigate the new electronic state by using FeTe Method Fe Te a b c a b SDW transition was suggested A. Subedi et. al, PRB, 78, 134514 (2008) Cleaved

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D(r,eV):Density of State of sample Sample was cleaved in ultra high vacuum Temperature 6.8K Pressure 10 -8 Pa Scanning Tunneling Microscopy/Spectroscopy(STM/STS) LT-UHV-STM/STS Feedback Circuit Controller DoS FF F +V bias V bias E e-e- V I tip sample tip sample

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Experiments Sample preparation Sample was prepared by chemical vapor transport method using I 2 nominal ratio Fe:Te=1:0.9 Put In evacuated quartz tube and keep 700 for one week. The sample was evaluated by energy dispersive X-ray spectroscopy. Prepared sample 1mm Good single crystalline sample was obtained

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Electrical property measurement 3 He cryostat system T = 0.5K 300K DC four probes method Resistivity measurement Magnetization measurement SQUID Magnetometer T = 2 K 300 K

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58K SQUID H = 0.5T AFM transition at 58K 58K DC four probes Heating anomaly at 58K SDW transition Result of Resistivity and magetization measurement

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STM Experimental Result (T=7.8K) 3.8 Te atom V bias : 0.9V I tunnel : 0.7nA Current image 1nm Discovery of charge stripe structure 3.8 Cleaved c

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A B A 012 3 [nm] B 012 3 A B We can see the iron layer under the tellurium layer. Te Fe Analyzing Stripe Structure

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C 0 1 2 [nm] C C Two types of iron atoms form charge stripe structure Analyzing Stripe Structure2

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STS Experimental Result (T=7.8K) SDW gap structure T SDW ~58K SDW =9meV

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The model of SDW induced charge stripe structure When SDW was formed on iron layer. nesting vector[110] Ferromagnetic structure Antiferromagnetic structure Antiferromagnetic and ferromagnetic direction by SDW. Crystal Structure: 4-fold rotation Spin Structure: 2-fold rotation

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Other Electrons have strong coulomb interaction +Reducing rotation symmetry caused by SDW SDW induced charge stripe structure Reduce off-site coulomb interaction

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SDW Charge Stripe The image of our model

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Charge Order and Charge Stripe at Strong correlated system Charge order in organic conductors H. Seo, JPSJ, 69,No. 3,805(2000) Strong coulomb interaction relate to charge stripe structure. J. M. Tranquada et. al, Nature,375, 561 (1995) Charge stripe in HTSC Anisotropic structure & Charge localize Mott-insulator Base Stripe

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Strong Correlative Systems Organic Conductors Low transfer energy Anisotropic crystal structure Cuprate Superconductors High on-site coulomb energy Isotropic crystal structure Mott-insulator base(half-filled) Iron-based Superconductors High off-site coulomb energy Isotropic crystal structure (Semi)Metal base New E-Crystal MX 1

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How do we form the stripe structure by isotropic interaction without structural anisotropy? Isotropic repulsive interaction particle form stripe structure on simulation. G. Malescio and G. Pellicane, Nature Materials, 2, 97 (2003) Can Charges form stripe structure only themselves?

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Summary Make single crystalline sample of FeTe Discover the charge stripe structure on FeTe by STM Propose the model of SDW induced charge stripe structure Results and Disscusion Thank you very much for your attention. MX 1 series is new materials of two dimensional crystal.