Pseudogap and related charge dynamics in Nd_2-xCe_xCuO_4
Abstract
The discovery of superconductivity in electron-doped cuprate has demonstrated the electron-hole symmetry in high-T_ c superconductor. This has laid a strong constraint on theories of the high-Tc mechanism. Further comparative study on the electron- and hole-doped systems may also provide useful information to examine controversial issues such as the pseudogap one. To discuss the similarities and differences between electron- and hole-doped systems, we have investigated temperature- and doping-variation of optical and transport properties in the typical electron-doped cuprate, Nd_2-xCe_xCuO4 (0 ≤ x ≤ 0.15)[1,2]. In the optical spectra of underdoped crystals (x < 0.15), a notable pseudogap is observed at low temperatures. Drude-like response evolves concomitantly with the pseudogap formation. Both the magnitude (Δ_PG) and the onset temperature (T) of the pseudogap decrease with electron-doping, while holding the relation that Δ_PG ≈ 10k_BT^*. The Δ_PG is comparable to the magnitude of the pseudogap at around (π /2, π /2) in the photoemission spectra reported by Armitage et al.[3], which indicates that the pseudogap appearing in the optical spectra is identical to that discerned by the photoemission spectroscopy. In accord with the evolution of the Drude response, the in-plane resistivity begins to decrease rapidly at around T^* in the underdoped region. The out-of-plane resistivity shows even more distinct decrease below T^*. This is because the inter-plane charge transport is governed by the electronic states at around (π ,0), where the quasi-particle spectral weight is accumulated in the case of the electron-doped system. This is contrary to the hole-doped case with the pseudogap around this point. The origin of the pseudogap has been ascribed to the antiferromagnetic spin correlation. The pseudogap phenomenon in the electron-doped cuprate will be discussed comparatively with that of the hole-doped cuprate. [1] Y. Onose et al., Phys. Rev. Lett. 87, 217001 (2001). [2] Y. Onose et al., to be published in Phys. Rev. B. [3] N. P. Armitage et al., Phys. Rev. Lett. 88, 257001 (2002).
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MAR.P1003O