Article

# Quantum oscillations in electron doped high temperature superconductors

(Impact Factor: 3.66). 12/2009; 82(9). DOI: 10.1103/PhysRevB.82.094515
Source: arXiv

ABSTRACT Quantum oscillations in hole doped high temperature superconductors are difficult to understand within the prevailing views. An emerging idea is that of a putative normal ground state, which appears to be a Fermi liquid with a reconstructed Fermi surface. The oscillations are due to formation of Landau levels. Recently the same oscillations were found in the electron doped cuprate, $\mathrm{Nd_{2-x}Ce_{x}CuO_{4}}$, in the optimal to overdoped regime. Although these electron doped non-stoichiometric materials are naturally more disordered, they strikingly complement the hole doped cuprates. Here we provide an explanation of these observations from the perspective of density waves using a powerful transfer matrix method to compute the conductance as a function of the magnetic field. Comment: An expanded version, accepted in Phys. Rev. B,

0 Followers
·
310 Views
• Source
• "Assuming that the mean free paths for the hole and the electron pockets are more or less the same, the pockets with larger k F will be strongly suppressed because of the exponential sensitivity. This appears to be reasonable from whatever numerical calculations and approximate analytical calculations exist [65] [22]. Nonetheless, the definitive result in the resistive state of YBCO, including vortex fluctuations, is missing. "
##### Article: Quantum oscillations and key theoretical issues in high temperature superconductors from the perspective of density waves
[Hide abstract]
ABSTRACT: High temperature superconductivity in cuprate superconductors remains an unsolved problem in theoretical physics. The same statement can also be made about a number of other superconductors that have been dubbed novel. What makes these superconductors so elusive is an interesting question in itself. This paper focuses on the recent magnetic oscillation experiments and how they fit into the broader picture. Many aspects of these experiments can be explained by Fermi liquid theory; the key issue is the extent to which this is true. If true, the entire paradigm developed over the past three decades must be reexamined. A critical analysis of this issue has necessitated a broader analysis of questions about distinct ground states of matter, which may be useful in understanding other novel superconductors.
Reports on Progress in Physics 01/2011; 74(2):022501. DOI:10.1088/0034-4885/74/2/022501 · 15.63 Impact Factor
• Source
##### Article: Advances in single crystal growth and annealing treatment of electron-doped HTSC
[Hide abstract]
ABSTRACT: High quality electron-doped HTSC single crystals of Pr2−xCexCuO4+δ and Nd2−xCexCuO4+δ have been successfully grown by the container-free traveling solvent floating zone technique. The optimally doped Pr2−xCexCuO4+δ and Nd2−xCexCuO4+δ crystals have transition temperatures T c of 25 K and 23.5 K, respectively, with a transition width of less than 1 K. We found a strong dependence of the optimal growth parameters on the Ce content x. We discuss the optimization of the post-growth annealing treatment of the samples, the doping extension of the superconducting dome for both compounds as well as the role of excess oxygen. The absolute oxygen content of the as-grown crystals is determined from thermogravimetric experiments and is found to be ≥ 4.0. This oxygen surplus is nearly completely removed by a post-growth annealing treatment. The reduction process is reversible as demonstrated by magnetization measurements. In as-grown samples the excess oxygen resides on the apical site O(3). This apical oxygen has nearly no doping effect, but rather influences the evolution of superconductivity by inducing additional disorder in the CuO2 layers. The very high crystal quality of Nd2−xCexCuO4+δ is particularly manifest in magnetic quantum oscillations observed on several samples at different doping levels. They provide a unique opportunity of studying the Fermi surface and its dependence on the carrier concentration in the bulk of the crystals.
The European Physical Journal Special Topics 10/2010; 188(1):61-72. DOI:10.1140/epjst/e2010-01297-8 · 1.76 Impact Factor
• Source
##### Article: Progress and perspectives on electron-doped cuprates
[Hide abstract]
ABSTRACT: Although the vast majority of high-$T_c$ cuprate superconductors are hole-doped, a small family of electron-doped compounds exists. Under investigated until recently, there has been tremendous recent progress in their characterization. A consistent view is being reached on a number of formerly contentious issues, such as their order parameter symmetry, phase diagram, and normal state electronic structure. Many other aspects have been revealed exhibiting both their similarities and differences with the hole-doped compounds. This review summarizes the current experimental status of these materials, with a goal to providing a snapshot of our current understanding of electron-doped cuprates. When possible we put our results in the context of the hole-doped compounds. We attempt to synthesize this information into a consistent view on a number of topics important to both this material class as well as the overall cuprate phenomenology including the phase diagram, the superconducting order parameter symmetry, phase separation, pseudogap effects, the role of competing orders, the spin-density wave mean-field description of the normal state, and electron-phonon coupling. Comment: 69 pages, 58 figures; Subitted to Reviews of Modern Physics on May 30th, 2009. Accepted February 23, 2010; http://rmp.aps.org/abstract/RMP/v82/i3/p2421_1
Review of Modern Physics 06/2009; 82(3). DOI:10.1103/RevModPhys.82.2421 · 42.86 Impact Factor