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Zurab Guguchia Physik-Institut der Universität Zürich, Switzerland

Zurab Guguchia Physik-Institut der Universität Zürich, Switzerland Laboratory for Muon Spin Spectroscopy, Paul- Scherrer Institut , Switzerland. Negative Oxygen Isotope Effect on the Static Spin Stripe Order in La 1.875 Ba 0.125 CuO 4. Tbilisi State University. Thank you!.

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Zurab Guguchia Physik-Institut der Universität Zürich, Switzerland

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  1. ZurabGuguchia Physik-InstitutderUniversität Zürich, Switzerland Laboratory for Muon Spin Spectroscopy,Paul-ScherrerInstitut, Switzerland Negative Oxygen Isotope Effect on the Static Spin Stripe Order in La1.875Ba0.125CuO4

  2. Tbilisi State University Thank you! Alexander Shengelaya Markus Bendele Hugo Keller Laboratory for Muon Spin Spectroscopy (PSI) Rustem Khasanov Laboratory for Developments and Methods (PSI) Ekaterina Pomjakushina Kazimierz Conder

  3. Outline • Introduction • Stripe phase in cuprates. • Isotope effects. • Muon Spin Rotation (µSR) technique. • Results • Oxygen Isotope Effect (OIE) on superconductivity in LBCO-1/8. • OIE on the static spin stripe order in LBCO-1/8. • Pressure effects in LBCO-1/8. • Conclusions

  4. Superconductivity in La2-xBaxCuO4 Hücker et al, Phys. Rev. B 83, 104506 (2011). Moodenbaugh et al, Phys. Rev. B 38, 4596 (1988). Axe et al, Phys. Rev. Lett. 62, 2751 (1989).

  5. Experimental evidence for static stripes in La1.48Nd0.4Sr0.12CuO4Neutron Scattering Spin order Real space Charge order Guguchia, PhD thesis,University of Zürich (2013). M. Vojta, Adv. Phys. 58, 699 (2009) and references therein. T. Wu et. al., Nature 477, 191 (2011). Tranquada et al, Nature (London) 375, 561 (1995).

  6. Central issues in Cuprates • What is microscopic origin of the stripe formation? The stripe phase may be caused by electronic and/or electron-lattice interaction. • Do stripes promote or inhibit superconductivity? Do they contain all ingredients required for stripe formation? Zaanen and Gunnarson Phys. Rev. B 40, 7391 (1989). White and Scalapino, PRL 80, 1272 (1998). Emery and Kivelson, Physica C 209, 597 (1993). M. Vojta, Adv. Phys. 58, 699 (2009).

  7. Conventional superconductivity Electron-phonon interaction Isotope effect: BCS: Ranges from 0.2-0.5 in elemental metals Weak coupling BCS predicts a value of a = 0.5 J. Bardeen et. al., Phys. Rev. 108, 1175 (1957). C.A. Reynolds et. al., Phys. Rev. 78, 487 (1950). E. Maxwell, Phys. Rev. 78, 477 (1950).

  8. Unconventional Oxygen Isotope effects (OIE’s) in cuprates Shengelaya et. al, PRL 83, 24 (1999). Khasanovet. al., PRL 101, 077001 (2008). Lanzaraet. al., J. Phys. Condens. Matter 11, L541 (1999). Rubio Temprano et. al., PRL 84, 1990 (2000). Zhech et. al., Nature 371, 681–683, 1994. J. Hofer et. al., PRL 84, 4192 (2000). K.A. Müller, J. Phys. Condens. Matter 19, 251002 (2007). H. Keller et. al., Materials today 11, 9 (2008).

  9. Isotope effect on Tc near 1/8 M.K. Crawford et. al., Science 250, 1390 (1990). G.M. Zhao et. al., J. Phys.: Condens. Matter 10, 9055 (1998). J.P. Franck et. al., PRL 71, 283 (1993). J. Hofer et. al., PRL 84, 4192 (2000). B. Batlogg et. al., PRL 59, 912 (1987). G.Y. Wang et. al., PRB 75, 212503 (2007).

  10. Muon-spin rotation (μSR) technique TRIUMF http://neutron.magnet.fsu.edu/muon_relax.html

  11. time (ms) μSR in magnetic materials homogeneous inhomogeneous time (ms) amplitude → magnetic volume fractionfrequency → average local magnetic field Damping → magnetic field distribution / magnetic fluctuations Courtesy of H. Luetkens

  12. Magnetization experiments Z. Guguchia et al., Phys. Rev. Lett. (2014). Tranquada et. al., PRB 78, 174529 (2008). Li et. al., PRL 99, 067001 (2007). Z. Guguchia et al., New Journal of Physics 15, 093005 (2013).

  13. Isotope effect on Tc in La1.875Ba0.125CuO4 Z. Guguchia et al., Phys. Rev. Lett. (2014).

  14. Oxygen Isotope effect on Tso Z. Guguchia et al., Phys. Rev. Lett. (2014).

  15. Oxygen Isotope effect on Tso Z. Guguchia et al., Phys. Rev. Lett. (2014).

  16. Oxygen Isotope effect on Tso G.M. Luke et. al., Physica C 185-9, 1175 (1991). B. Nachumi et. al., PRB 58, 8760 (1998). Z. Guguchia et al., Phys. Rev. Lett. (2014).

  17. OIE effect on Tso and magnetic fraction Vm Z. Guguchia et al., Phys. Rev. Lett. (2014).

  18. Summary of the OIE studies on La1.875Ba0.125CuO4 Give evidence for stripe-lattice coupling in cuprates. Superconductivity and stripe order are competing phenomena.

  19. Pressure experiments with SQUID and µSR SQUID (Maisuradze and Guguchia) (R. Khasanov) µSR Z. Guguchiaet al., New Journal ofPhysics15, 093005 (2013).

  20. Pressure effect on static spin-stripe order in La1.875Ba0.125CuO4 Vsc(0) + Vm(0) ≈ 1 Z. Guguchia et al., New Journal of Physics 15, 093005 (2013).

  21. LTT structural phase under pressure Hücker et al, PRL 104, 057004 (2010).

  22. Pressure effect on the isotope effect inLBCO-1/8

  23. Conclusions • Large negative OIE’s were observed on Tso and Vm in La2-xBaxCuO4 (x = 1/8). • Oxygen-isotope shifts of Tc and TSO are sign reversed. Stripe order and superconductivity are competing orders. • The electron-lattice interaction is involved in the stripe formation and is a crucial factor controlling the competition between the stripe order and superconductivity. • A purely electronic mechanism can not explain the present isotope and pressure experiments!

  24. Thank you very much for your attention!

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