Magnetic Breakdown in the Electron-Doped Cuprate Superconductor ${\mathrm{Nd}}_{2-x}{\mathrm{Ce}}_x{\mathrm{CuO}}_4$: The Reconstructed Fermi Surface Survives in the Strongly Overdoped Regime

We report on semiclassical angle-dependent magnetoresistance oscillations and the Shubnikov–de Haas effect in the electron-overdoped cuprate superconductor ${\mathrm{Nd}}_{2-x}{\mathrm{Ce}}_x{\mathrm{CuO}}_4$. Our data provide convincing evidence for magnetic breakdown in the system. This shows that a reconstructed multiply connected Fermi surface persists, at least at strong magnetic fields, up to the highest doping level of the superconducting regime.

Figure 1

(a) Sketch of the experimental configuration. (b) Interlayer resistivity ${\rho }_c$ of a slightly overdoped NCCO sample ($x=0.16$) as a function of tilt angle $\theta$, at different temperatures. The range $|\theta |<75°$ corresponds to the normal conducting state; the rapid drop of ${\rho }_c$ outside this range is due to onset of superconductivity. The vertical dashed lines are drawn through the AMRO features centered at $|\theta |\approx 53°$, which are independent of temperature and magnetic field strength. (c) Second derivative of the resistivity in (b) exhibiting dips at the AMRO peak positions. (d) Same as (b) for a strongly overdoped sample ($x=0.17$).

Figure 2

Dependence of the positions of the AMRO features in NCCO with $x=0.16$ (blue circles) and 0.17 (red stars) on the azimuthal orientation $\phi$ of the field rotation plane. Dashed lines are guides to the eye.

Figure 3

Slow and fast SdH oscillations in the interlayer resistance of a strongly overdoped, $x=0.17$, NCCO crystal recorded at two different temperatures. The data are normalized to the field-dependent nonoscillating background resistance. The inset shows high-field fragments of the data, demonstrating regular fast oscillations.

Figure 4

Frequency of the slow SdH oscillations (left scale) and the corresponding Fermi surface area (right scale) as a function of the electron doping level $x$. The dashed line is a guide to the eye.