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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
Stripe Structure Usually occur with anisotropic interaction Long range attractive interaction Short range repulsive interaction Ex)Dipole-Dipole interaction
New Type Strong correlated system Iron-based Superconductors La-O Fe-P LaFePO(1111) W. F. Wang et. al. New J. Phys. 11 045003(2009) Coexistence of magnetism and superconductivity
Magnets and Iron-based Superconductors Iron-based Superconductor Magnet New Phase? ex)Fe, Ni, Co Spin andCharge ex)LaFePO,BaFe2As2 Spin Density Wave(SDW) Main Character Spin rspin Main Character Charge Strong Weak Spin-Spin Interaction Our Purpose Investigate the new electronic state
FeTe Fe Te Cleaved a c b SDW transition was suggested b a A. Subediet. al, PRB, 78, 134514 (2008) Method Investigate the new electronic state by using FeTe
Scanning Tunneling Microscopy/Spectroscopy(STM/STS) tip sample Feedback Circuit Controller tip V I sample E e- D(r,eV):Density of State of sample εF+Vbias εF LT-UHV-STM/STS DoS DoS Temperature 6.8KPressure 10-8Pa Sample was cleaved in ultra high vacuum Vbias
Experiments Sample preparation Sample was prepared by chemical vapor transport method using I2 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
Electricalproperty measurement Resistivity measurement 3Hecryostat system T = 0.5K～300K DC four probes method Magnetization measurement SQUIDMagnetometer T = 2 K～300 K
Result of Resistivity and magetization measurement 58K DC four probes Heating SQUIDH = 0.5T 58K AFM transition at 58K anomaly at 58K SDW transition
STM Experimental Result (T=7.8K) Cleaved c 3.8Å Teatom 3.8Å 1nm Discovery of charge stripe structure Vbias: 0.9V Itunnel: 0.7nA Current image
Analyzing Stripe Structure B A B A B 3 0 1 2 [nm] Fe Te We can see the iron layer under the tellurium layer. A 3 0 1 2 [nm]
Analyzing Stripe Structure2 C C C Two types of iron atoms form charge stripe structure 0 2 1 [nm]
STS Experimental Result (T=7.8K) TSDW~58K DSDW=9meV SDW gap structure
The model of SDW induced charge stripe structure When SDW was formed on iron layer. nesting vector Antiferromagnetic structure Antiferromagnetic and ferromagnetic direction by SDW. Crystal Structure: 4-fold rotation Spin Structure: 2-fold rotation Ferromagnetic structure
Other Electrons have strong coulomb interaction +Reducing rotation symmetry caused by SDW Reduce off-site coulomb interaction SDW induced charge stripe structure
The image of our model SDW Charge Stripe
Charge Order and Charge Stripe at Strong correlated system Charge stripe in HTSC Charge order in organic conductors H. Seo, JPSJ, 69,No. 3,805(2000) Anisotropic structure & Charge localize J. M. Tranquada et. al, Nature,375, 561 (1995) Mott-insulator Base Stripe Strong coulomb interaction relate to charge stripe structure.
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) New E-Crystal MX1 Iron-based Superconductors ・High off-site coulomb energy ・Isotropic crystal structure ・(Semi)Metal base
How do we form the stripe structure by isotropic interactionwithout structural anisotropy? G. Malescio and G. Pellicane, Nature Materials, 2, 97 (2003) Isotropic repulsive interaction particle form stripe structure on simulation. Can Charges form stripe structure only themselves?
Summary Results and Disscusion Make single crystalline sample of FeTe Discover the charge stripe structure on FeTe by STM Propose the model of SDW induced charge stripe structure MX1 series is new materials of two dimensional crystal. Thank you very much for your attention.