Alix McCollam

Emergence of the nematic electronic state in FeSe

We present a comprehensive study of the evolution of the nematic electronic structure of FeSe using high-resolution angle-resolved photoemission spectroscopy (ARPES), quantum oscillations in the normal state, and elastoresistance measurements. Our high-resolution ARPES allows us to track the Fermi surface deformation from fourfold to twofold symmetry across the structural transition at ∼87K, which is stabilized as a result of the dramatic splitting of bands associated with dxz and dyz character in the presence of strong electronic interactions. The low-temperature Fermi surface is that of a compensated metal consisting of one hole and two electron bands and is fully determined by combining the knowledge from ARPES and quantum oscillations. A manifestation of the nematic state is the significant increase in the nematic susceptibility approaching the structural transition that we detect from our elastoresistance measurements on FeSe. The dramatic changes in electronic structure cannot be explained by the small lattice distortion and, in the absence of magnetic fluctuations above the structural transition, point clearly towards an electronically driven transition in FeSe, stabilized by orbital-charge ordering.

Evolution of the Fermi Surface of BaFe2(As1-xPx)2 on Entering the Superconducting Dome

Using the de Haas-van Alphen effect we have measured the evolution of the Fermi surface of BaFe2(As1-xPx){2} as a function of isoelectric substitution (As/P) for 0.41<x<1 (T{c} up to 25 K). We find that the volumes of electron and hole Fermi surfaces shrink linearly with decreasing x. This shrinking is accompanied by a strong increase in the quasiparticle effective mass as x is tuned toward the maximum T{c}. These results are not explained by simple band structure calculations, and it is likely that these trends originate from the same many-body interactions which give rise to superconductivity.

Pressure-tuned insulator to metal transition in eu2ir2o7

We have studied the effect of pressure on the pyrochlore iridate Eu

Magnetic-Field Dependence of theYbRh2Si2Fermi Surface

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de Haas-van Alphen Study of the Fermi Surfaces of Superconducting LiFeP and LiFeAs

Ir

Fermi surface of IrTe2 in the valence-bond state as determined by quantum oscillations

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Crystal Growth, Structure, and Incoherent Metallic Behaviour of FeCrAs

O

Field-induced magnetic transitions inCa10(Pt3As8)((Fe1−xPtx)2As2)5compounds

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Field-induced nematic-like magnetic transition in an iron pnictide superconductor, Ca

, which at ambient pressure has a thermally driven insulator to metal transition at

_{10}

T_{MI}sim120