Fermi-Surface Reconstruction and Wiedemann-Franz Law in a Cuprate Superconductor

Date

Feb 24, 2015

Time

11:00 AM - 1:00 PM

Speaker

Prof. Louis Taillefer

Affiliation

University of Sherbrooke, Canada, Canadian Institute for Advanced Research

Language

en

Main Topic

Chemie

Other Topics

Physik, Chemie

Host

Prof. Dr. A. P. Mackenzie

Description

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 temperature. A signature of this reconstruction is the change of sign in the Hall [2] and Seebeck [3] coefficients, which become negative at low temperature. Observed in other hole-doped cuprates [3,4,5], this phenomenon is generic. By analogy with Eu-LSCO, where charge modulations are responsible 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 transport measurements in high magnetic fields to investigate the Fermi-surface reconstruction in YBCO, its impact on superconductivity and the nature of the high-field normal state. Based on our recent observation of a hole-like 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 across the phase diagram and find a dramatic drop in Hc2 below a critical doping p = 0.18 [12]. This shows that phase competition is what shapes the Tc dome in hole-doped cuprates. We have measured the thermal and electrical Hall 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 liquid at T = 0. This imposes strict limits on the theory of underdoped cuprates. [1] N. Doiron-Leyraud et al., Nature 447, 565 (2007). [2] D. LeBoeuf et al., Nature 450, 533 (2007). [3] J. Chang et al., Physical Review Letters 104, 057005 (2010). [4] N. Doiron-Leyraud et al., Physical Review 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. Ghiringhelli et al., Science 337, 821 (2012). [8] J. Chang et al., Nature Physics 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. Grissonnanche et al., Nature Communications 5, 3280 (2014). [13] G. Grissonnanche et al., to be published.

Links

• MPI CPfS

Last modified: Feb 25, 2015, 3:07:39 AM