Tuning the quantum critical point by Mn impurities
Tuning the quantum critical point by Mn impurities and chemical pressure in La. Fe. As. O 0. 89 F 0. 11 Samuele Sanna Physics Department University of PAVIA, Italy Sanna, SIF 2015, 24 th September 2015
Coworkers P. Carretta, M. Moroni University of PAVIA, Italy R. De Renzi, P. Bonfà, S. Bordignon, G. Allodi Univ. of PARMA, Italy F. Hammerath, B. Büchner, G. Prando, R. Kappenberger, S. J. Singh, S. Wurmehl IFW Dresden, Germany M. Moroni Univ. Pavia F. Hammerath R. Kappenberger IFW Dresden Sanna, SIF 2015, 24 th September 2015 T. Shiroka, ETH, Zürich, Switzerland Y. Kobayashi, M. Sato, Nagoya University, Japan G. Lamura, M. Putti CNR-SPIN and Univ. of GENOVA, Italy P. Carretta Univ. Pavia R. De Renzi Univ. Parma
Tuning magnetism and superconductivity in 1111 REFe. As. O (RE 1111) RE Charge doping, e. g. F O Hydrostatic pressure Chemical pressure Substitution Mn Fe Sanna, SIF 2015, 24 th September 2015
F O REFe. As. O: e- charge doping RE = La Luetkens et al, Nature Materials (2009) RE = Sm Sanna et al, PRB 80, 052503 (2009) La. Fe. As. O 1 -x. Fx Sm. Fe. As. O 1 -x. Fx SDW Sanna, SIF 2015, 24 th September 2015
Fe/Mn substitution in optimally F-doped RE 1111 Sm. Fe. As. O 1 -z. Fz Hammerat PRB 92, 020505(R) (2015) Sanna PRB (2009) Sm La 0. 8 Y 0. 2 Mn con ten t La Mn is a poison for SC in RE=La ! Less than 0. 2%of Mn is enough to kill SC Process heavily affected by chemical pressure Sanna, SIF 2015, 24 th September 2015
Fe/Mn substitution in optimally F-doped RE 1111 La. Fe 1 -x. Mnx. As. O 0. 89 F 0. 11 x=0 -0. 002 ≈ isoelectronic conditions Mn Magnetic SC Sato et al. , JPSJ 79, 014710 (2010) Resistivity is rapidly increased Charge localization by Mn Hammerath et al. PRB 89, 134503 (2014) Mn quickly restores static magnetism Sanna, SIF 2015, 24 th September 2015
Evidence for a QCP La. Fe 1 -x. Mnx. As. O 0. 89 F 0. 11 Magnetic correlation length x=0 -0. 002 ≈ isoelectronic conditions Magnetic SC Hammerath et al. PRB 89, 134503 (2014) 2 D AFM spin fluctuations @ QCP Sanna, SIF 2015, 24 th September 2015 La. Fe. As. O 0. 89 F 0. 11 very close to a QCP!
Chemical pressure and Mn impurity effects unpublished Mn drives the system through a QCP Chemical pressure moves the QCP away Magnetic correlations depressed by a smaller ion Why ? For stripe collinear order magnetism enhanced for smaller RE Giovannetti Nat. Commun. 2, 398 (2011) Orthomagnetic order induced by Mn ? Gastiasoro & Andersen, PRL 113, 067002 (2014) Sanna, SIF 2015, 24 th September 2015 Nanoscopic coexistence Q=(p/a, 0) E R E TH NO Q=(p/a, p/a)
Chemical pressure and Mn impurity effects unpublished Mn drives the system through a QCP Chemical pressure moves the QCP away Superconductivity suppressed by Mn Why ? 1) Mn suppresses (p/a, 0) fluctuations which sustain superconductivity 2) Mn induces charge localization 3) Mn pins the stripes Hammerat PRB 92, 020505(R) (2015) Sanna, SIF 2015, 24 th September 2015 Nanoscopic coexistence
Main conclusions (and questions) REFe 1 -x. Mnx. As. O 0. 89 F 0. 11 optimally F-doped • Mn is a poison for SC in La 1111 (xc=0. 002 !) possible orthomagnetic order? • Chemical pressure moves away the QCP why ? ? R U O Y R O SF K N A H T MANY ! ! N O I T N ATTE Sanna, SIF 2015, 24 th September 2015 PRB 89, 134503 (2014) PRB 92, 020505(R) (2015)
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