198 research outputs found
Heavy surface state in a possible topological Kondo insulator: Magneto-thermoelectric transport on the (011)-plane of SmB
Motivated by the high sensitivity to Fermi surface topology and scattering
mechanisms in magneto-thermoelectric transport, we have measured the
thermopower and Nernst effect on the (011)-plane of the proposed topological
Kondo insulator SmB. These experiments, together with electrical
resistivity and Hall effect measurements, demonstrate that the (011)-plane also
harbors a metallic surface with the effective mass in the order of 10-10
. The surface and bulk conductances are well distinguished in these
measurements and are categorized into metallic and non-degenerate
semiconducting regimes, respectively. Electronic correlations play an important
role in enhancing scattering and also contribute to the heavy surface state.Comment: 4 figures, 1 tabl
Spin gap and magnetic resonance in superconducting BaFeNiAs
We use neutron spectroscopy to determine the nature of the magnetic
excitations in superconducting BaFeNiAs ( K).
Above the excitations are gapless and centered at the commensurate
antiferromagnetic wave vector of the parent compound, while the intensity
exhibits a sinusoidal modulation along the c-axis. As the superconducting state
is entered a spin gap gradually opens, whose magnitude tracks the
-dependence of the superconducting gap observed by angle resolved
photoemission. Both the spin gap and magnetic resonance energies are
temperature \textit{and} wave vector dependent, but their ratio is the same
within uncertainties. These results suggest that the spin resonance is a
singlet-triplet excitation related to electron pairing and superconductivity.Comment: 4 pages, 4 figure
Phase diagram of CeFeAsPO obtained from electric resistivity, magnetization, and specific heat measurements
We performed a systematic study on the properties of CeFeAsPO
() by electrical resistivity, magnetization and specific heat
measurements. The c-axis lattice constant decreases significantly with
increasing P content, suggesting a remarkable chemical pressure. The Fe-3d
electrons show the enhanced metallic behavior upon P-doping and undergo a
magnetic quantum phase transition around . Meanwhile, the Ce-4f
electrons develop a ferromagnetic order near the same doping level. The
ferromagnetic order is vanishingly small around . The data suggest a
heavy-fermion-like behavior as . No superconductivity is observed
down to 2 K. Our results show the ferromagnetic ordered state as an
intermediate phase intruding between the antiferromagnetic bad metal and the
nonmagnetic heavy fermion metal and support the cerium-containing iron
pnictides as a unique layered Kondo lattice system.Comment: 7 pages, 6 figures, text and figures revised, references added
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