Benjamin A Frandsen

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Understanding the role played by broken-symmetry states such as charge, spin and orbital orders in the mechanism of emergent properties, such as high-temperature superconductivity, is a major current topic in materials research. That the order may be within one unit cell, such as nematic, was only recently considered theoretically, but its observation in(More)
Diluted magnetic semiconductors have received much attention due to their potential applications for spintronics devices. A prototypical system (Ga,Mn)As has been widely studied since the 1990s. The simultaneous spin and charge doping via hetero-valent (Ga(3+),Mn(2+)) substitution, however, resulted in severely limited solubility without availability of(More)
We report the successful synthesis and characterization of a new type I-II-V bulk form diluted magnetic semiconductor (DMS) Li(Zn,Mn,Cu)As, in which charge and spin doping are decoupled via (Cu,Zn) and (Mn,Zn) substitution at the same Zn sites. Ferromagnetic transition temperature up to  ∼33 K has been observed with a coercive field  ∼40 Oe for the 12.5%(More)
RENiO3 (RE=rare-earth element) and V2O3 are archetypal Mott insulator systems. When tuned by chemical substitution (RENiO3) or pressure (V2O3), they exhibit a quantum phase transition (QPT) between an antiferromagnetic Mott insulating state and a paramagnetic metallic state. Because novel physics often appears near a Mott QPT, the details of this(More)
The origin of magnetism in metals has been traditionally discussed in two diametrically opposite limits: itinerant and local moments. Surprisingly, there are very few known examples of materials that are close to the itinerant limit, and their properties are not universally understood. In the case of the two such examples discovered several decades ago, the(More)
We present a temperature-dependent atomic and magnetic pair distribution function (PDF) analysis of neutron total scattering measurements of antiferromagnetic MnO, an archetypal strongly correlated transition-metal oxide. The known antiferromagnetic ground-state structure fits the low-temperature data closely with refined parameters that agree with(More)
We report the synthesis and characterization of a bulk form diluted magnetic semiconductor, (La(1-x)Ca(x))(Zn(1-y) Mn(y))AsO, with a layered crystal structure isostructural to that of the 1 1 1 1 type Fe-based high-temperature superconductor LaFeAsO and the antiferromagnetic LaMnAsO. With Ca and Mn codoping into LaZnAsO, the ferromagnetic ordering occurs(More)
An experimental determination of the magnetic pair distribution function (mPDF) defined in an earlier paper [Frandsen et al. (2014). Acta Cryst. A70, 3-11] is presented for the first time. The mPDF was determined from neutron powder diffraction data from a reactor and a neutron time-of-flight total scattering source on a powder sample of the(More)
In its orthorhombic T d polymorph, MoTe2 is a type-II Weyl semimetal, where the Weyl fermions emerge at the boundary between electron and hole pockets. Non-saturating magnetoresistance and superconductivity were also observed in T d-MoTe2. Understanding the superconductivity in T d-MoTe2, which was proposed to be topologically non-trivial, is of eminent(More)
Benjamin A. Frandsen,1 Zizhou Gong,1 Maxwell W. Terban,2 Soham Banerjee,2 Bijuan Chen,3 Changqing Jin,3 Mikhail Feygenson,4 Yasutomo J. Uemura,1 and Simon J. L. Billinge2,5,* 1Department of Physics, Columbia University, New York, New York 10027, USA 2Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA(More)