Electron pockets in the Fermi surface of hole-doped high-Tc superconductors

Abstract

High-temperature superconductivity in copper oxides occurs when the materials are chemically tuned to have a carrier concentration intermediate between their metallic state at high doping and their insulating state at zero doping. The underlying evolution of the electron system in the absence of superconductivity is still unclear, and a question of central importance is whether it involves any intermediate phase with broken symmetry. The Fermi surface of the electronic states in the underdoped 'YBCO' materials YBa2Cu3O(y) and YBa2Cu4O8 was recently shown to include small pockets, in contrast with the large cylinder that characterizes the overdoped regime, pointing to a topological change in the Fermi surface. Here we report the observation of a negative Hall resistance in the magnetic-field-induced normal state of YBa2Cu3O(y) and YBa2Cu4O8, which reveals that these pockets are electron-like rather than hole-like. We propose that these electron pockets most probably arise from a reconstruction of the Fermi surface caused by the onset of a density-wave phase, as is thought to occur in the electron-doped copper oxides near the onset of antiferromagnetic order. Comparison with materials of the La2CuO4 family that exhibit spin/charge density-wave order suggests that a Fermi surface reconstruction also occurs in those materials, pointing to a generic property of high-transition-temperature (T(c)) superconductors.

Chemical potential oscillations from nodal Fermi surface pocket in the underdoped high-temperature superconductor YBa2Cu3O6+x

“…Translational symmetry-breaking models proposed thus far are either nodal-antinodal (for example, refs 11,12), which would be inconsistent with the current experimental results, or comprise solely nodal hole pockets 13 , which would be difficult to reconcile with negative Hall and Seebeck effect 4,20 , leaving us with a dilemma. Possible resolutions to this problem involve understanding how a negative Hall and Seebeck effect can arise from a nodal Fermi surface pocket 30,31 .…”

“…A lthough high-T c cuprate superconductors have a history spanning a quarter of a century 1,2 , quantum oscillations in these materials have only been measured as recently as a few years ago [3][4][5][6][7][8][9][10][11][12] , by employing high magnetic fields to weaken superconductivity. Interestingly, their advent has signalled a reevaluation of the electronic structure in the normal state of the underdoped cuprates.…”

“…Quantum oscillation results have been interpreted in terms of a nodal-antinodal Fermi surface 4,9,11,12 arising from spatial symmetry breaking, where the antinodal sections correspond to electron pockets 12 , and the nodal sections correspond either to closed hole pockets or open sheets 11 in models proposed thus far. Multiple frequencies can arise not only from closed sections such as these, but also from warping, splitting, and magnetic breakdown effects of a single Fermi surface section.…”

“…Against this backdrop of contradictory scenarios, an unambiguous interpretation of quantum oscillation results in terms of momentum space location, charge carrier type, and single or multiple surfaces in the case of the underdoped cuprates has remained elusive [3][4][5][6][7][8][9][10] . Quantum oscillations in the case of a fixed chemical potential cannot discern the sign of charge carriers or whether there are single or multiple types of charge carrier present 17 , causing recourse, thus far, to less direct probes such as the Hall effect and thermopower, and calculations of the electronic structure to infer a nodal-antinodal Fermi surface 4,9,[18][19][20] .…”

“…Quantum oscillations in the case of a fixed chemical potential cannot discern the sign of charge carriers or whether there are single or multiple types of charge carrier present 17 , causing recourse, thus far, to less direct probes such as the Hall effect and thermopower, and calculations of the electronic structure to infer a nodal-antinodal Fermi surface 4,9,[18][19][20] .…”