1,205 research outputs found
Quantum Griffiths phase in CePd(1-x)Rh(x) with x ~ 0.8
The magnetic field dependence of the magnetisation () and the temperature
dependence of the ac susceptibility () of CePd(1-x)Rh(x) single
crystals with are analysed within the frame of the
quantum Griffiths phase scenario, which predicts and
with . All vs and
vs data follow the predicted power-law behaviour. The parameter
, extracted from , is very sensitive to the Rh content
and varies systematically with from -0.1 to 0.4. The value of ,
derived from measurements on a \cpr single crystal, seems to be rather
constant, , in a broad range of temperatures between 0.05
and 2 K and fields up to about 10 T. All observed signatures and the
values are thus compatible with the quantum Griffiths scenario.Comment: 4 pages, 3 figure
Huge First-Order Metamagnetic Transition in the Paramagnetic Heavy-Fermion System CeTiGe
We report on the observation of large, step-like anomalies in the
magnetization (\,/Ce), in the magnetostriction
(), and in the magnetoresistance in
polycrystals of the paramagnetic heavy-fermion system CeTiGe at a critical
magnetic field 12.5\,T at low temperatures. The size of
these anomalies is much larger than those reported for the prototypical
heavy-fermion metamagnet CeRuSi. Furthermore, hysteresis between
increasing and decreasing field data indicate a real thermodynamic, first-order
type of phase transition, in contrast to the crossover reported for
CeRuSi. Analysis of the resistivity data shows a pronounced decrease of
the electronic quasiparticle mass across . These results establish CeTiGe
as a new metamagnetic Kondo-lattice system, with an exceptionally large,
metamagnetic transition of first-order type at a moderate field.Comment: 5 pages, 4 figure
Non-Fermi liquid states in the pressurized system: two critical points
In the archetypal strongly correlated electron superconductor CeCuSi
and its Ge-substituted alloys CeCu(SiGe) two quantum
phase transitions -- one magnetic and one of so far unknown origin -- can be
crossed as a function of pressure \cite{Yuan 2003a}. We examine the associated
anomalous normal state by detailed measurements of the low temperature
resistivity () power law exponent . At the lower critical point
(at , ) depends strongly on Ge
concentration and thereby on disorder level, consistent with a
Hlubina-Rice-Rosch scenario of critical scattering off antiferromagnetic
fluctuations. By contrast, is independent of at the upper quantum
phase transition (at , ), suggesting critical
scattering from local or Q=0 modes, in agreement with a density/valence
fluctuation approach.Comment: 4 pages, including 4 figures. New results added. Significant changes
on the text and Fig.
Dual-path state reconstruction scheme for propagating quantum microwaves and detector noise tomography
Quantum state reconstruction involves measurement devices that are usually
described by idealized models, but not known in full detail in experiments. For
weak propagating microwaves, the detection process requires linear amplifiers
which obscure the signal with random noise. Here, we introduce a theory which
nevertheless allows one to use these devices for measuring all quadrature
moments of propagating quantum microwaves based on cross-correlations from a
dual-path amplification setup. Simultaneously, the detector noise properties
are determined, allowing for tomography. We demonstrate the feasibility of our
novel concept by proof-of-principle experiments with classical mixtures of weak
coherent microwaves.Comment: 11 pages, 3 figure
Tunable coupling engineering between superconducting resonators: from sidebands to effective gauge fields
In this work we show that a tunable coupling between microwave resonators can
be engineered by means of simple Josephson junctions circuits, such as dc- and
rf-SQUIDs. We show that by controlling the time dependence of the coupling it
is possible to switch on and off and modulate the cross-talk, boost the
interaction towards the ultrastrong regime, as well as to engineer red and blue
sideband couplings, nonlinear photon hopping and classical gauge fields. We
discuss how these dynamically tunable superconducting circuits enable key
applications in the fields of all optical quantum computing, continuous
variable quantum information and quantum simulation - all within the reach of
state of the art in circuit-QED experiments.Comment: 11 pages, 4 figure
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