Event Detail

Striped Superconductors

John Tranquada, Brookhaven National Laboratory

(11/17/09) 4:30 p.m. 700 Clark Hall

High temperature superconductivity occurs in close proximity to antiferromagnetism in both the long-studied copper oxides and the newer iron-based superconductors. Magnetic excitations are commonly believed to play an important role in the electron pairing necessary for the superconducting state, but there are divergent ideas on how they are involved.  I will discuss our studies of one particular system, La_2-xBa_xCuO₄, which exhibits coexistence of locally antiferromagnetic order and an unusual superconducting state.  Focusing on the x=1/8 composition, neutron and x-ray diffraction studies show that charge and spin stripe order develop below 53~K and 40~K, respectively [1,2].  The usual bulk superconductivity is strongly suppressed, with a transition temperature T_c ~ 5 K; nevertheless, susceptibility and resistivity measurements provide evidence for the onset of two-dimensional superconducting correlations at 40 K, together with the spin stripe order [2,3].  To explain the electronic decoupling of the CuO₂ layers, a form of striped superconductivity, also called a pair density wave, has been proposed [4,5].  I will discuss the potential relevance of these results to other cuprates.

 

[1] M. Fujita et al., Phys. Rev. B 70, 104517 (2004).

[2] J. M. Tranquada et al., Phys. Rev. B 78, 174529 (2008).

[3] Q. Li et al., Phys. Rev. Lett. 99, 067001 (2007).

[4] E. Berg et al., Phys. Rev. Lett. 99, 127003 (2007).

[5] E. Berg et al., arXiv:0901.4826.