Shubnikov-de Haas quantum oscillations reveal a reconstructed Fermi surface near optimal doping in a thin film of the cuprate superconductorPr1.86Ce0.14CuO4±δ

Abstract

We study magnetotransport properties of the electron-doped superconductor Pr2−xCexCuO 4±δ with x = 0.14 in magnetic fields up to 92 T, and observe Shubnikov de-Haas magnetic quantum oscillations. The oscillations display a single frequency F =255±10 T, indicating a small Fermi pocket that is ∼ 1% of the two-dimensional Brillouin zone and consistent with a Fermi surface reconstructed from the large hole-like cylinder predicted for these layered materials. Despite the low nominal doping, all electronic properties including the effective mass and Hall effect are consistent with overdoped compounds. Our study demonstrates that the exceptional chemical control afforded by high quality thin films will enable Fermi surface studies deep into the overdoped cuprate phase diagram.Understanding the ordering phenomena that compete or coexist with superconductivity in the cuprate superconductors remains an outstanding challenge. Central to this effort is identification of Fermi surface (FS) topology and evolution with doping via studies of magnetic quantum oscillations (QO), led by initial observation of QO in hole-doped YBa 2 Cu 3 O 6.5 [1,2]. In hole-doped cuprates, QO studies have shown (1) a large cylindrical hole-like FS consistent with band theory in overdoped Tl 2 Ba 2 CuO 6+δ [3], (2) FS reconstruction and a complex topology in underdoped YBa 2 Cu 3 O 6+δ [4], and (3) strong enhancements in the quasiparticle effective mass [5]; see Refs. 6 and 7 for further reviews. These observations have been interpreted as evidence for competing electronic ordered phases and the influence of quantum critical fluctuations, crossing over to Fermiology consistent with the band-theory picture. Comparable experimental studies of electron-doped cuprates are limited, and precise description of their FS remains an outstanding challenge. Here we report on the FS topology and effective mass in the electron-doped cuprate Pr 2−x Ce x CuO 4±δ (PCCO) with x = 0.14. We observe Shubnikov-de Haas QO in a PCCO thin film measured in extreme magnetic fields up to 92 T, where magnetotransport data (Fig. 1) riers assuming the electron dopant concentration is equal to the Ce content x in Pr 2−x Ce x CuO 4±δ . Photoemission (ARPES) experiments are consistent with a large FS in overdoped n-doped materials [10][11][12], and show evidence for both electron-and hole-like pockets as x decreases below ∼ 0.16. However, many issues remain unresolved, including the structure of the FS and nature of its reconstruction and evolution with doping, reconciling quantum oscillation measurements with the observation of Fermi arcs [13,14] in the pseudogap phase, and identifying the true nature of the competing ground state (whether arising from observed magnetic [15,16]

Quantum oscillations from the reconstructed Fermi surface in electron-doped cuprate superconductors

“…Our FS area values are also comparable to those seen in PCO films [25]. Compared to recently published results on PCCO films of x=0.14 [21], where the frequency is 255 T and m e =0.43, our PCCO x=0.15 data disagree substantially. However, note that near optimal doping, a hump is typically observed in the MR, and the absence of such a feature suggests that the sample in [9] actually may have a doping level comparable to our x=0.16 sample, which has no hump.…”

“…Rather than measuring the unreconstructed FS, magnetic breakdown involving tunneling between the electron and hole pockets was suggested to be responsible for the high frequency oscillations [19]. Additionally, Breznay et al observed SdH oscillations of the in-plane MR in PCCO thin films (x≈x o , x=0.14) [21]. However, only the small hole pockets are observable in quantum oscillations for both PCCO and NCCO at x 0 .…”

Fermi surface reconstruction in electron-doped cuprates without antiferromagnetic long-range order

“…3F), which is consistent with our inability to observe a gap beyond x=0. 16. Such a behavior of gap closing near x=0.16~0.17 is consistent with a quantum critical point (QCP) in that doping range, as suggested by a x to 1-x density transition in transport experiments (13,18,19).…”

“…Both the back-bending behavior (folded band) and gap opening have been observed at all doping levels we measured (x=0.11, x=0.15, x=0. 16), demonstrating that the FS reconstruction persists to the over-doped regime. This is consistent with QOM (12)(13)(14)(15)(16)(17), and the well-defined gap suggests that a magnetic breakdown in QOM is less likely below x=0.16.…”

Understanding electron-doped cuprate superconductors as hole superconductors

“…Quantum oscillations have also been observed in underdoped HgBa 2 CuO 4+δ [63,64], with frequency 840T corresponding to about 3% of the Brillouin zone, or 0.061 carriers per pocket. Several other such observations in hole-doped cuprates have been reported [65][66][67]. Whether these oscillations are due to hole pockets or electron pockets or both has been controversial [68,69] and is unsettled.…”