[seminar] SEMINAR na IF-u u PETAK, 27. 05. 2011. u 10:00

[Ivica Zivkovic]

*
*

*Institut za fiziku, Bijenička cesta 46,*

*predavaonica u zgradi Mladen Paić*

*petak, 27. svibnja 2011, u 10:00 sati*


*Doping, Strains, Disorder and Electric Field Effect on*

*Superconductivity in Ultra-Thin La*_*2-x* *Sr*_*x* *CuO*_*4* *Films*


*Prof. Davor Pavuna*


*Physics of Complex Matter, Station 3, *

*EPFL, CH-1015 Lausanne, Switzerland*

/*E-mail: */_/*davor.pavuna at epfl.ch*/ 
<mailto:zvonko.trontelj at fmf.uni-lj.si>_


*I briefly review main results of our systematic experiments on strained 
thin films of LSCO-214 grown by laser ablation [1-3], and then discuss 
recent method to smoothly tune the carrier concentration of MBE grown 
LSCO monolayer by means of an applied electric field [4,5]. Thin film 
devices were made in an electrical double layer transistor configuration 
utilizing an ionic liquid as gate electrolyte. **Very large fields and 
induced changes in surface carrier density enable shifts in the critical 
temperature by up to 30 K. As **reported elsewhere in more detail [4], 
dozens of reproducible resistance vs temperature and carrier density 
curves were recorded and have shown to collapse onto a single function 
as predicted for a two-dimensional superconductor-insulator transition. 
The observed critical resistance is precisely the quantum resistance for 
pairs, R*_*Q* * = h/(2e)*^*2* * = 6.45 k?, suggestive of a phase 
transition driven by quantum phase fluctuations, and Cooper pair 
(de)localization. The implications of these results and the ongoing 
field effect studies on other materials will also be discussed [5].*

*1. D. Pavuna et al., Journal of Physics 108, 012040 (2008) and 
references therein*

*2. C. Cancellieri et al., Phys. Rev. B76, 174520 (2007); EPFL Thesis 
no. 4120 (2008)*

*3. D. Ariosa et al. Appl. Phys. Lett. 92, 092506 (2008) and references 
therein*

*4. A. T. Bollinger, G. Dubuis, J. Yoon, D. Pavuna, J. Misewich, I. 
Bozovic, Nature 472, 458 (2011)*

*5. G. Dubuis, A. T. Bollinger, D. Pavuna, I. Bozovic, unpublished (2011) *


_/*http://cream.epfl.ch/page-31521-en.html*/_

*Voditelji seminara IF-a: Vlasta Horvatić i Ivica Živković*



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