Novel Superconducting Phases in Copper Oxides and Iron-oxypnictides: NMR Studies

Yoshio Kitaoka; Hidekazu Mukuda; Sunao Shimizu; Shin-ichiro Tabata; Parasharam M. Shirage; Akira Iyo

doi:10.1016/j.jpcs.2010.10.020

paper

Novel Superconducting Phases in Copper Oxides and Iron-oxypnictides: NMR Studies

arXiv:1101.3928 · doi:10.1016/j.jpcs.2010.10.020

Abstract

We reexamine the novel phase diagrams of antiferromagnetism (AFM) and high-Tc $s u p er co n d u c t i v i t y (H T S C) f or a d i sor d er - f r ee C u O$ _2 $pl an e ba se d o nan e v a l u a t i o n o f l oc a l h o l e d e n s i t y ($ p $) b y s i t e - se l ec t i v e C u - N M R s t u d i eso nm u l t i l a y er e d co pp er o x i d es . M u l t i l a y er e d sy s t e m s p r o v i d e u s w i t h t h eo pp or t u ni t y t or ese a r c h t h ec ha r a c t er i s t i cso f t h e d i sor d er - f r ee C u O$ _2 $pl an e . T h es i t e - se l ec t i v e N M R i s t h e b es t an d t h eo n l y t oo l u se d t oe x t r a c tl a y er - d e p e n d e n t c ha r a c t er i s t i cs . C o n se q u e n tl y, w e ha v eco n c l u d e d t ha tt h e u ni f or mmi x in g o f A F M an d S C i s a g e n er a l p r o p er t y inh er e n tt o a s in g l e C u O$ _2 $pl an e inan u n d er d o p e d r e g im eo f H T S C . T h e$ T $= 0 p ha se d ia g r am o f A F M co n s t r u c t e d h er e i s in q u an t i t a t i v e a g r ee m e n tw i t h t h e t h eor i es ina s t r o n g cor r e l a t i o n r e g im e w hi c hi s u n c han g e d e v e n w i t hm o bi l e h o l es . T hi s Mottphysics pl a y s a v i t a l r o l e f or m e d ia t in g t h e C oo p er p ai r s t o mak e$ T_c $o f H T S C v er y hi g h . B y co n t r a s t, w e a dd r ess f r o m e x t e n s i v e N M R s t u d i eso n e l ec t r o n - d o p e d i r o n - o x y p ni c t i d es L a 1111 co m p o u n d s t ha tt h e in cr e a se in$ T_c $i s n o t d u e t o t h e d e v e l o p m e n t o f A F M s p in f l u c t u a t i o n s, b u t b ec a u se t h es t r u c t u r a l p a r am e t er s, s u c ha s t h e b o n d an g l e$ α $o f t h e F e A s$ _4 $t e t r ah e d r o nan d t h e a - a x i s l e n g t h, a pp r o a c h e a c h o pt im u m v a l u e . B a se d o n t h eser es u l t s, w e p r o p ose t ha t a s t r o n g er cor r e l a t i o nin H T S C t hanin F e A s - ba se d s u p er co n d u c t or s ma y mak e$ T_c$ higher significantly.

5 pages, 4 figures, accepted for publication in J.Phys.Chem.Solids (2010)

Novel Superconducting Phases in Copper Oxides and Iron-oxypnictides: NMR Studies

Abstract

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