Greg Boebinger

Comparative High Field Magneto-transport Of Rare Earth Oxypnictides With Maximum Transition Temperatures

We compare magnetotransport of the three iron-arsenide-based compounds ReFeAsO (Re=La, Sm, Nd) in very high DC and pulsed magnetic fields up to 45 and 54 T, respectively. Each sample studied exhibits a superconducting transition temperature near the maximum reported to date for that particular compound. While high magnetic fields do not suppress the superconducting state appreciably, the resistivity, Hall coefficient, and critical magnetic fields, taken together, suggest that the phenomenology and superconducting parameters of the oxypnictide superconductors bridges the gap between MgB{sub 2} and YBCO.

Scale-invariant magnetoresistance in a cuprate superconductor

Cranking up the field Cuprate superconductors have many unusual properties even in the “normal” (nonsuperconducting) regions of their phase diagram. In the so-called “strange metal” phase, these materials have resistivity that scales linearly with temperature, in contrast to the usual quadratic dependence of ordinary metals. Giraldo-Gallo et al. now find that at very high magnetic fields—up to 80 tesla—the resistivity of the thin films of a lanthanum-based cuprate scales linearly with magnetic field as well, again in contrast to the expected quadratic law. This dual linear dependence presents a challenge for theories of the normal state of the cuprates. Science, this issue p. 479 At high magnetic fields up to 80 tesla, the resistivity of a thin-film La-based cuprate scales linearly with the field. The anomalous metallic state in the high-temperature superconducting cuprates is masked by superconductivity near a quantum critical point. Applying high magnetic fields to suppress superconductivity has enabled detailed studies of the normal state, yet the direct effect of strong magnetic fields on the metallic state is poorly understood. We report the high-field magnetoresistance of thin-film La2–xSrxCuO4 cuprate in the vicinity of the critical doping, 0.161 ≤ p ≤ 0.190. We find that the metallic state exposed by suppressing superconductivity is characterized by magnetoresistance that is linear in magnetic fields up to 80 tesla. The magnitude of the linear-in-field resistivity mirrors the magnitude and doping evolution of the well-known linear-in-temperature resistivity that has been associated with quantum criticality in high-temperature superconductors.

Giant Hole‐Phonon Coupling In a Strongly Interacting Two‐Dimensional (2D) Hole System

We have studied the temperature dependent phonon emission rate P(T) of a strongly interacting (rs⩾22) dilute 2D metallic GaAs hole system through carrier heating experiment. We observe that P(T) changes from P(T) ∼ T5 to P(T) ∼ T7 above 100mK, indicating a crossover from screened piezoelectric(PZ) coupling to screened deformation potential(DP) coupling for hole‐phonon scattering. Quantitative comparison with theory shows that the short range DP coupling between the low density holes and phonons is more than ten times stronger than expected in the poorly understood 2D metallic state (E. Abrahams, S.V. Kravchenko, and M.P. Sarachik, Rev. Mod. Phys. 73, 251(2001)). The long range PZ coupling between holes and phonons, however, has an expected magnitude.