Seminar FO

Electronic orders and the the Fermi surface reconstruction in the cuprate superconductors
Wojciech Tabiś
Institute of Solid State Physics
Vienna University of Technology
wojciech.tabis@tuwien.ac.at
A major difficulty in understanding high-Tc systems is the complexity of the materials, the presence of strong electron-electron interactions, and their rich phase diagrams. Synchrotron X-ray scattering is a powerful tool allowing to explore the electronic and structural degrees of freedom of complex materials. Furthermore, high magnetic fields play an important role in studying the high-Tc phenomenon, because such fields weaken the superconducting state and enable us to explore the competing states. One of such states is the spontaneous self-organized charge modulation, so called the charge density wave (CDW) order. Although its presence has been demonstrated within the CuO2 plane of each family of cuprate superconductors [1], the extent of the CDW order as a function of doping, temperature, or magnetic field remains controversial.
I will present our recent results of the resonant X-ray scattering experiments in the model cuprate
HgBa2CuO4+δ (Hg1201). While resonant X-ray scattering (RXS) allowed us to establish the dopingtemperature range of the static CDW or-der in this compound [2,3], resonant inelastic X-ray scattering (RIXS) enabled the discovery of the short range CDW correlations at temperatures exceeding the onset of the static correlations observed by RXS. Such coexistence of static and dynamic CDW correlations is consistent with theoretical predictions [4]. The following electronic transport measurements in magnetic fields up to 70 T allowed to investigate the reconstruction of the Fermi surface by the CDW order. Recent X-ray diffraction experiments at magnetic fields up to 28 T have shown that in addition to the mdescribed above CDW order within CuO2 planes, an additional 3D charge order sets in at fields above approximately 18 T in the cuprate YBa2Cu3O6+x (YBCO) [5]. Our recent XAS measurements in fields up to 30 T suggest that the Cu-O chains, specific to this compound, contribute in the formation of this additional 3D CDW order. This demonstrates, that the 3D electronic order may be specific to YBCO and
not generic to the cuprates. The combined results allow to draw a universal electronic phase diagram of the cuprates.

[1] R. Comin and A. Damascelli, Annu. Rev. Condens. Matter Phys. 7, 369 (2016)
[2] W. Tabis et al., Nature Commun. 5, 5875 (2014).
[3] W. Tabis et al., Phys. Rev. B 96, 134510 (2017).
[4] S. Caprara et al., Phys. Rev. B 95, 224511 (2017)
[5] S. Gerber et al., Science 350, 949 (2015)