1.  Single crystals of YBCO: P. Lejay (Grenoble), D. Colson, A. Forget (SPEC)  Electron irradiation Laboratoire des Solides Irradiés (Ecole Polytechnique) Disorder, Superconducting fluctuations and Metal-Insulator crossover in high T c cuprates F. Rullier-Albenque 1, H. Alloul 2, 1 Service de Physique de l’Etat Condensé, CEA, Saclay, France. 2 Physique des Solides, Université Paris-Sud, Orsay, France F. Balakirev 3, C. Proust 4 3 NHMFL, Los Alamos National Laboratory, New Mexico, USA 4 Laboratoire National des Champs Magnétiques Pulsés, Toulouse, France 500  m

2.  Influence of controlled disorder on T c, T * and the MIC of YBCO Zn substitution Electron irradiation  Conclusion Phase diagram including disorder  Superconducting fluctuations, Nernst effect and magnetoresistance SC fluctuations in « pure » YBCO Influence of disorder Disorder, Superconducting fluctuations and Metal-Insulator crossover in high T c cuprates  Introduction Generic phase diagram of the cuprates Presence of incipient disorder?

3. « Generic » phase diagram of the cuprates? Magnetic fluctuations T c max Number of holes/ CuO 2 plane PG AFAF SC underdoped optimal overdoped 0 0.10.20.3 Strange metal SG This shape of phase diagram is apparently generic But only established in the particular case of La 2-x Sr x CuO 4 x = hole doping The optimal T c is not generic Hole doping not always very well determined

4. Some questions about High T c cuprates Magnetic fluctuations T c max Number of holes/ CuO 2 plane PG AFAF SC underdoped optimal overdoped 0 0.10.20.3 Strange metal Pseudogap: Phase transition? Crossover? Link with superconductivity? Metal-Insulator transition Importance of magnetic correlations at least for underdoped materials Transition to a Fermi liquid? Pseudogap joins T c curve or QCP ??

5. Significant Nernst signal at T>Tc Signature of superconducting fluctuations in the normal state T c = loss of long range phase coherence La 2-x Sr x Cu O 4 Anomalous Nernst effect in the normal state of cuprates Effect more pronounced in underdoped samples Possible implications for the physics of the pseudogap regime: preformed pairs? Wang et al, PRB 64 (2001) TcTc

6. Metal – Insulator crossover in low T c cuprates? 30T 60T Ono et al, PRL 2000 Metal-Insulator transition Induced by the magnetic field Competition between AF and SC low T c cuprates LaSrCuO La-Bi2201 High magnetic field to suppress superconductivity Low T upturns in  (T) Role of intrinsic disorder?

7. Native disorder in the pure cuprate families Disorder is detrimental to superconductivity Some uncontrolled disorder is present in LSCO and Bi2201 Correlation between   and optimum T c The optimum T c and the residual resistivity   depend on the family 0 1 2 3 4 5 050100150200250300 R 2D (k  / ) T (K) YBCO 7 Bi-2201 r La-Bi2201 

8. Comparison of the one layer cuprate families Planar 17 O NMR linewidths at optimal doping YBCO 7 20% of K s

9.  Influence of controlled disorder on T c, T * and the MIC Zn substitution Electron irradiation  Conclusion Phase diagram including disorder  Superconducting fluctuations, Nernst effect and magnetoresistance SC fluctuations in « pure » YBCO Influence of disorder Disorder, Superconducting fluctuations and Metal-Insulator crossover in high T c cuprates  Introduction Generic phase diagram of the cuprates Presence of incipient disorder?

10. Influence of defects on the phase diagram T* + 4%Zn T c decreases more rapidly in underdoped samples H. Alloul et al, PRL (1991) Increase of the disordered magnetism range The position of the optimal T c shifts with disorder Phase diagram including disorder No change of hole doping No change of T *

11. Low T electron irradiation No diffusion of defects Cryostat coupled to a Hydrogen cryogenerator Irradiation at 20K Electron irradiation Point defects homogeneously distributed Elastic collisions between electrons and target nuclei Proton irradiation Heavy ion irradiation Different from : Cluster of defects, columnar defects Vortex pinning studies

12.  T c  Influence of irradiation defects on the transport properties Same single crystals Excellent control of defect content down to T c =0 The transition curves remain very sharpHomogeneous damage Optimally doped overdoped Matthiessen’s rule well obeyed at high T : F. Rullier Albenque et al, Europhysics Letters 50, 81 (2000), PRL (2003)

13. T c =25K Resistivity upturns= MIC? F. Rullier-Albenque et al, Europhysics Letters (2008). High field suppresses SC and reveals upturns in irradiated samples Metallic behavior in pure YBCO 6.6 Upturns related to the presence of defects 55T

14. 4% 3% 1.5% 8% Resistivity upturns = MIC? Matthiessen’s rule well obeyed at high T : Log(1/T) behavior at high enough T Downward deviations in some cases

15. Resistivity upturns vs defect contents in YBCO 6.6 1.5 k  / 2.2 3.0 3.8 4.8 In-situ measurements For low defect content :  2D < 5k  /  scales with  0 Kondo like scattering on defects  saturates at low T

16.     For k F l e >>1 (R 2D <<26k  )  in (T) ~ T p Rullier-Albenque et al, PRL 87 (2001) In overdoped samples 2D weak localization effects induced by disorder Underdoped YBCO 6.6 compared to overdoped Tl2201 Overdoped Tl2201 Purely elastic scattering by the defects

17. Spin glass phase and MIC in the Phase Diagram SG and MIC are determined by disorder

18. Irradiated YBCO compared to « pure» low T c Cuprates Controlled disorder Introduced in a pure system The upturns are quantitatively similar Driven by disorder Specific disorder reduces T c F. Rullier-Albenque et al, Europhysics Letters 81, 37008 (2008).

19. The various cuprate families in the phase diagram ? Phase diagram in the absence of disorder

20.  Influence of controlled disorder on T c, T * and the MIC Zn substitution Electron irradiation  Conclusion Phase diagram including disorder  Superconducting fluctuations, Nernst effect and magnetoresistance SC fluctuations in « pure » YBCO Influence of disorder Disorder, Superconducting fluctuations and Metal-Insulator crossover in high T c cuprates  Introduction Generic phase diagram of the cuprates Presence of incipient disorder?

21. Nernst effect in pure YBCO 6.6 Rapid drop of the Nernst signal at T c T onset : 85K YBCO 6.6 T c =57K

22. T onset The temperature range of the Nernst signal increases with decreasing doping BUT T onset is higher in optimally doped than in underdoped YBCO Optimally doped YBCOUnderdoped YBCO Temperature extension of the Nernst signal in pure YBCO In pure YBCO 6.6, the Nernst signal extends up to ~85K much lower that the pseudogap temperature T * ~ 300K T onset

23. Transverse magnetoresistance under high magnetic fields H’ c Harris et al. PRL (1995) Magnetoresistance in the normal state Transverse magnetoresistivity in YBCO 7 High field measurements In YBCO 7 Onset of SC fluctuations around 140K

24. Phase diagram of pure YBCO How the range of superconducting fluctuations is altered by disorder ? Onset of fluctuations follows T c and not T * YBCO T*T* Nernst TcTc TcTc

25. Comparaison YBCO 6.6 and YBCO 7 In both compounds the T range of the Nernst signal expands with disorder Effect more pronounced in underdoped YBCO 6.6 F. Rullier-Albenque et al, PRL (2006) T c =5K T c =30K T c =57K T onset is nearly the same for all the samples Nernst effect in irradiated YBCO YBCO 6.6

26. Disorder and superconducting fluctuations in YBCO 6.6 Magnetoresistance data for the T c =6K sample Vortex solid TcTc F. Rullier-Albenque et al, PRL (2007)

27. Disorder and superconducting fluctuations in YBCO 6.6 With decreasing T c BUT remain quite large are depressedand TcTc Comparison with Nernst results systematically higher than T

28. Wang et al, PRB (2006) T c = 28K H c2 is nearly unchanged from low T to above T c Irradiated YBCO 6.6 T c = 25K « Pure » underdoped Bi 2 Sr 2-y La y Cu O 6 y=0.5 - T c = 28.9K Wang et al, PRB 64 (2001) Electron irradiated YBCO 6.6 T c = 24.6K (onset of magnetization) T onset ~ 75K Comparison between La-Bi2201 and irradiated YBCO 6.6

29. Spin glass, MIC, T c The different cuprate famlies Disorder Low T upturns of resistivity Not necessarily a MIC Pseudogap and fluctuation regime Increase of the regime of superconducting fluctuations Disorder, Superconducting fluctuations and Metal-Insulator crossover in high T c cuprates