Point contact spectroscopy (PCS) on the Fe122 pnictides and Fe11 chalcogenides

We present PCS results on Ba(Fe$_{1-x}$Co$_{x})_{2}$As$_{2}$ and Fe$_{1+y}$Te. The superconducting (S) crystals (x=0.08) show multigap like Andreev peaks. The non-S crystals (x=0.015, y=0.03) also show a conductance enhancement with split peaks at low temperatures (T). This conductance enhancement does not match with the bulk antiferromagnetic (AFM) transition T and survives up to 90 K for y=0.03 (T$_{N}\sim $69 K) and 130 K for x=0.015 (T$_{N}\sim $115 K). For the S samples in the coexisting regime (x=0.05 {\&} 0.055), in addition to the Andreev peaks below T$_{C}$, a zero bias conductance enhancement develops and survives for $\sim $5K above T$_{C}$. PCS detects conductance changes due to quasiparticles scattering off charge or spin ordering. These conductance enhancements may arise from orbital ordering as detected by photoemission spectroscopy$^{1}$ and AFM ordering (Q-scattering), respectively.$^{2}$ $^{1}$Yi et.al, arXiv:1011.0050. $^{2}$Bobkova et.al, PRL 94, 037005 (2005). UIUC work supported by NSF-DMR-0706013, U.S. DOE Award No.DE-AC02-98CH10886, BNL work by DOE Award No.DE-AC0298CH10886, Cambridge work by EPSRC, Trinity College, the Royal Society, the Commonwealth Trust. Ames Lab operated by ISU under DOE Contract No.DE-AC02-07CH11358.