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UID:DSC-8836
DTSTART;TZID=Europe/Berlin:20150224T110000
SEQUENCE:1424830059
TRANSP:OPAQUE
DTEND;TZID=Europe/Berlin:20150224T130000
URL:https://www.dresden-science-calendar.de/calendar/de/detail/8836
LOCATION:MPI-CPfS\, Nöthnitzer Straße 4001187 Dresden
SUMMARY:Taillefer: Fermi-Surface Reconstruction and Wiedemann-Franz Law in 
 a Cuprate Superconductor
CLASS:PUBLIC
DESCRIPTION:Speaker: Prof. Louis Taillefer\nInstitute of Speaker: Universit
 y of Sherbrooke\, Canada\, Canadian Institute for Advanced Research\nTopic
 s:\nPhysik\, Chemie\n Location:\n  Name: MPI-CPfS (Seminarraum 1+2\, Nöth
 nitzer Straße 40\, 01187 Dresden)\n  Street: Nöthnitzer Straße 40\n  Ci
 ty: 01187 Dresden\n  Phone: \n  Fax: \nDescription: Since the discovery of
  quantum oscillations in 2007 [1]\, we know that the Fermi surface of the 
 underdoped cuprate superconductor YBCO undergoes a reconstruction at low t
 emperature. A signature of this reconstruction is the change of sign in th
 e Hall [2] and Seebeck [3] coefficients\, which become negative at low tem
 perature. Observed in other hole-doped cuprates [3\,4\,5]\, this phenomeno
 n is generic. By analogy with Eu-LSCO\, where charge modulations are respo
 nsible for the reconstruction\, a similar mechanism was inferred for YBCO 
 [5]. Charge modulations in YBCO have since been observed directly by NMR [
 6] and X-ray diffraction [7\,8\,9]. Charge order has also been observed in
  other materials [10] – it represents a central new fact in the physics 
 of cuprates. We have used electrical\, thermal and thermo-electric transpo
 rt measurements in high magnetic fields to investigate the Fermi-surface r
 econstruction in YBCO\, its impact on superconductivity and the nature of 
 the high-field normal state. Based on our recent observation of a hole-lik
 e pocket in the Fermi surface of underdoped YBCO [11]\, I will argue that 
 both charge order and the pseudogap play a role in the reconstruction. We 
 have mapped out the upper critical field Hc2 as a function of doping acros
 s the phase diagram and find a dramatic drop in Hc2 below a critical dopin
 g p = 0.18 [12]. This shows that phase competition is what shapes the Tc d
 ome in hole-doped cuprates. We have measured the thermal and electrical Ha
 ll conductivities in YBCO to test the Wiedemann-Franz law and found it to 
 hold in the T = 0 limit\, thereby ruling out the possibility of a vortex l
 iquid at T = 0. This imposes strict limits on the theory of underdoped cup
 rates.  [1] N. Doiron-Leyraud et al.\, Nature 447\, 565 (2007). [2] D. LeB
 oeuf et al.\, Nature 450\, 533 (2007). [3] J. Chang et al.\, Physical Revi
 ew Letters 104\, 057005 (2010). [4] N. Doiron-Leyraud et al.\, Physical Re
 view X 3\, 021019 (2013). [5] F. Laliberté et al.\, Nature Communications
  2\, 432 (2011). [6] T. Wu et al.\, Nature 477\, 191 (2011). [7] G. Ghirin
 ghelli et al.\, Science 337\, 821 (2012). [8] J. Chang et al.\, Nature Phy
 sics 8\, 871 (2012). [9] A. J. Achkar et al.\, Physical Review Letters 109
 \, 167001 (2012). [10] R. Comin et al.\, Science 343\, 390 (2014). [11] N.
  Doiron-Leyraud et al.\, Nature Communications 6\, 6034 (2015). [12] G. Gr
 issonnanche et al.\, Nature Communications 5\, 3280 (2014). [13] G. Grisso
 nnanche et al.\, to be published.
DTSTAMP:20260630T003319Z
CREATED:20150213T075259Z
LAST-MODIFIED:20150225T020739Z
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