391 research outputs found
Antiferromagnetism and hot spots in CeIn
Enormous mass enhancement at ''hot spots'' on the Fermi surface (FS) of
CeIn has been reported at strong magnetic field near its antiferromagnetic
(AFM) quantum critical point [T. Ebihara et al., Phys. Rev. Lett. 93, 246401
(2004)] and ascribed to anomalous spin fluctuations at these spots. The ''hot
spots'' lie at the positions on FS where in non-magnetic LaIn the narrow
necks are protruded. In paramagnetic phase CeIn has similar spectrum. We
show that in the presence of AFM ordering its FS undergoes a topological change
at the onset of AFM order that truncates the necks at the ''hot spots'' for one
of the branches. Applied field leads to the logarithmic divergence of the dHvA
effective mass when the electron trajectory passes near or through the neck
positions. This effect explains the observed dHvA mass enhancement at the ''hot
spots'' and leads to interesting predictions concerning the spin-dependence of
the effective electron mass. The (T,B)-phase diagram of CeIn, constructed
in terms of the Landau functional, is in agreement with experiment.Comment: 4 pages, 1 figur
Field-induced quantum fluctuations in the heavy fermion superconductor CeCu2Ge2
Quantum-mechanical fluctuations in strongly correlated electron systems cause
unconventional phenomena such as non-Fermi liquid behavior, and arguably high
temperature superconductivity. Here we report the discovery of a field-tuned
quantum critical phenomenon in stoichiometric CeCu2Ge2, a spin density wave
ordered heavy fermion metal that exhibits unconventional superconductivity
under ~ 10 GPa of applied pressure. Our finding of the associated quantum
critical spin fluctuations of the antiferromagnetic spin density wave order,
dominating the local fluctuations due to single-site Kondo effect, provide new
information about the underlying mechanism that can be important in
understanding superconductivity in this novel compound.Comment: Heavy Fermion, Quantum Critical Phenomeno
Avpr1a variant associated with preschoolers' lower altruistic behavior
10.1371/journal.pone.0025274PLoS ONE69
Interplay of magnetism, Fermi surface reconstructions, and hidden-order in the heavy-fermion material URuSi
URuSi is surely one of the most mysterious of the heavy-fermion
compounds. Despite more than twenty years of experimental and theoretical
works, the order parameter of the transition at K is still
unknown. The state below remains called "hidden-order phase" and the
stakes are still to identify the energy scales driving the system to this
phase. We present new magnetoresistivity and magnetization measurements
performed on very-high-quality single crystals in pulsed magnetic fields up to
60 T. We show that the transition to the hidden-order state in URuSi is
initially driven by a high-temperature crossover at around 40-50 K, which is a
fingerprint of inter-site electronic correlations. In a magnetic field
applied along the easy-axis , the vanishing of this
high-temperature scale precedes the polarization of the magnetic moments, as
well as it drives the destabilization of the hidden-order phase. Strongly
impurity-dependent magnetoresistivity confirms that the Fermi surface is
reconstructed below and is strongly modified in a high magnetic field
applied along , i.e. at a sufficiently-high magnetic polarization.
The possibility of a sharp crossover in the hidden-order state controlled by a
field-induced change of the Fermi surface is pointed out.Comment: 10 pages, 6 figures, accepted in Physical Review
Dichotomy between the hole and electrons behavior in the multiband FeSe probed by ultra high magnetic fields
Magnetoresistivity \r{ho}xx and Hall resistivity \r{ho}xy in ultra high
magnetic fields up to 88T are measured down to 0.15K to clarify the multiband
electronic structure in high-quality single crystals of superconducting FeSe.
At low temperatures and high fields we observe quantum oscillations in both
resistivity and Hall effect, confirming the multiband Fermi surface with small
volumes. We propose a novel and independent approach to identify the sign of
corresponding cyclotron orbit in a compensated metal from magnetotransport
measurements. The observed significant differences in the relative amplitudes
of the quantum oscillations between the \r{ho}xx and \r{ho}xy components,
together with the positive sign of the high-field \r{ho}xy , reveal that the
largest pocket should correspond to the hole band. The low-field
magnetotransport data in the normal state suggest that, in addition to one hole
and one almost compensated electron bands, the orthorhombic phase of FeSe
exhibits an additional tiny electron pocket with a high mobility.Comment: Latex, 4 pages (2 figures, 1 table), and supplemental materia
Quenched nematic criticality separating two superconducting domes in an iron-based superconductor under pressure
The nematic electronic state and its associated nematic critical fluctuations
have emerged as potential candidates for superconducting pairing in various
unconventional superconductors. However, in most materials their coexistence
with other magnetically-ordered phases poses significant challenges in
establishing their importance. Here, by combining chemical and hydrostatic
physical pressure in FeSeS, we provide a unique access to a
clean nematic quantum phase transition in the absence of a long-range magnetic
order. We find that in the proximity of the nematic phase transition, there is
an unusual non-Fermi liquid behavior in resistivity at high temperatures that
evolves into a Fermi liquid behaviour at the lowest temperatures. From quantum
oscillations in high magnetic fields, we trace the evolution of the Fermi
surface and electronic correlations as a function of applied pressure. We
detect experimentally a Lifshitz transition that separates two distinct
superconducting regions: one emerging from the nematic electronic phase with a
small Fermi surface and strong electronic correlations and the other one with a
large Fermi surface and weak correlations that promotes nesting and
stabilization of a magnetically-ordered phase at high pressures. The lack of
mass divergence suggests that the nematic critical fluctuations are quenched by
the strong coupling to the lattice. This establishes that superconductivity is
not enhanced at the nematic quantum phase transition in the absence of magnetic
order.Comment: 4 figures, 9 page
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