E. J. Singley

Impurity Band Conduction in a High Temperature Ferromagnetic Semiconductor

The band structure of a prototypical dilute magnetic semiconductor (DMS), Ga1-xMnxAs, is studied across the phase diagram via infrared and optical spectroscopy. We prove that the Fermi energy (EF) resides in a Mn-induced impurity band (IB). Specifically the changes in the frequency dependent optical conductivity [sigma1(omega)] with carrier density are only consistent with EF lying in an IB. Furthermore, the large effective mass (m*) of the carriers inferred from our analysis of sigma1(omega) supports this conclusion. Our findings demonstrate that the metal to insulator transition in this DMS is qualitatively different from other III-V semiconductors doped with nonmagnetic impurities. We also provide insights into the anomalous transport properties of Ga1-xMnxAs.

Electron dynamics in Nd 1.85 Ce 0.15 CuO 4 + δ : Evidence for the pseudogap state and unconventional c -axis response

Infrared reflectance measurements were made with light polarized along the a and c axes of both superconducting and antiferromagnetic phases of electron doped

Sum rules and electrodynamics of high-T c cuprates in the pseudogap state

{\mathrm{Nd}}_{1.85}{\mathrm{Ce}}_{0.15}{\mathrm{CuO}}_{4+\ensuremath{\delta}}.

Global trends in the interplane penetration depth of layered superconductors

The results are compared to characteristic features of the electromagnetic response in hole doped cuprates. Within the

Infrared probe of the insulator-to-metal transition in Ga1−xMnxAs and Ga1−xBexAs

{\mathrm{CuO}}_{2}

Interlayer conductivity in the superconductor Tl 2 Ba 2 CuO 6¿d : Energetics and energy scales

planes the frequency dependent scattering rate, 1/\ensuremath{\tau}(\ensuremath{\omega}), is depressed below

Sum Rules and Interlayer Conductivity of High-Tc Cuprates

\ensuremath{\sim}650 {\mathrm{cm}}^{\ensuremath{-}1};

Infrared probe of itinerant ferromagnetism in Ga(1-x)Mn(x)As.

this behavior is a hallmark of the pseudogap state. While in several hole doped compounds the energy scales associated with the pseudogap and superconducting states are quite close, we are able to show that in

INFRARED PROBE OF THE ELECTRONIC STRUCTURE AND CARRIER SCATTERING IN NIMNSB THIN FILMS

{\mathrm{Nd}}_{1.85}{\mathrm{Ce}}_{0.15}{\mathrm{CuO}}_{4+\ensuremath{\delta}}

Electronic structure and carrier dynamics of the ferromagnetic semiconductor Ga 1¿x Mn x As

the two scales differ by more than one order of magnitude. Another feature of the in-plane charge response is a peak in the real part of the conductivity,