340 research outputs found
Rigid-Band Shift of the Fermi Level in a Strongly Correlated Metal: Sr(2-y)La(y)RuO(4)
We report a systematic study of electron doping of Sr2RuO4 by non-isovalent
substitution of La^(3+) for Sr^(2+). Using a combination of de Haas-van Alphen
oscillations, specific heat, and resistivity measurements, we show that
electron doping leads to a rigid-band shift of the Fermi level corresponding to
one doped electron per La ion, with constant many-body quasiparticle mass
enhancement over the band mass. The susceptibility spectrum is substantially
altered and enhanced by the doping but this has surprisingly little effect on
the strength of the unconventional superconducting pairing.Comment: 4 pages, 3 figure
Magnetic oscillations in planar systems with the Dirac-like spectrum of quasiparticle excitations II: transport properties
The quantum magnetic oscillations of electrical (Shubnikov de Haas effect)
and thermal conductivities are studied for graphene which represents a
distinctive example of planar systems with a linear, Dirac-like spectrum of
quasiparticle excitations. We show that if a utmost care was taken to separate
electron and phonon contributions in the thermal conductivity, the oscillations
of electron thermal conductivity, and the Lorenz number,
would be observable in the low field (less than a few Teslas) regime.Comment: 11 pages, RevTeX4, 6 EPS figures; 2 references, 1 figure and one more
section are added; final version published in PR
Berry phase and de Haas - van Alphen effect in LaRhIn
We explain the experimental data on the magnetization of recently
published by R. G. Goodrich et al. in Phys. Rev.Lett. {\bf 89}, 026401 (2002).
We show that the magnetization of a small electron group associated with a
band-contact line was detected in that paper. These data provide the first
observation of the Berry phase of electrons in metals via the de Haas - van
Alphen effect.Comment: 4 pages, 2 figure
Pressure induced softening of YB_6: pressure effect on the Ginzburg-Landau parameter \kappa=\lambda/\xi
Measurements of the transition temperature T_c, the second critical filed
H_{c2} and the magnetic penetration depth \lambda under hydrostatic pressure
(up to 9.2 kbar) in the YB_6 superconductor were carried out. A pronounced and
{\it negative} pressure effects (PE) on T_c and H_{c2} with dT_c/dp=-0.0547(4)
K/kbar and \mu_0dH_{c2}(0)/dp =-4.84(20) mT/kbar, and zero PE on \lambda(0)
were observed. The PE on the coherence length d\xi(0)/dp=0.28(2) nm/kbar was
calculated from the measured pressure dependence of H_{c2}(0). Together with
the zero PE on the magnetic penetration depth \lambda(0), our results imply
that the Ginzburg-Landau parameter \kappa(0)=\xi(0)/\lambda(0) depends on
pressure and that pressure "softens" YB_6, e.g. moves it to the type-I
direction.Comment: 4 pages, 2 figure
Evidence for charged critical behavior in the pyrochlore superconductor RbOs2O6
We analyze magnetic penetration depth data of the recently discovered
superconducting pyrochlore oxide RbOs2O6. Our results strongly suggest that in
RbOs2O6 charged critical fuctuations dominate the temperature dependence of the
magnetic penetration depth near Tc. This is in contrast to the mean-field
behavior observed in conventional superconductors and the uncharged critical
behavior found in nearly optimally doped cuprate superconductors. However, this
finding agrees with the theoretical predictions for charged criticality and the
charged criticality observed in underdoped YBa2Cu3O6.59.Comment: 5 pages, 4 figure
Universal linear relations between susceptibility and Tc in cuprates
We developed an experimental method for measuring the intrinsic
susceptibility \chi of powder of cuprate superconductors in the zero field
limit using a DC-magnetometer. The method is tested with lead spheres. Using
this method we determine \chi for a number of cuprate families as a function of
doping. A universal linear (and not proportionality) relation between Tc and
\chi is found. We suggest possible explanations for this phenomenon.Comment: Accepted for publication in PR
Nearly free electrons in the layered oxide superconductor Ag5Pb2O6
We present first measurements of quantum oscillations in the layered oxide
superconductor
Ag5Pb2O6. From a detailed angular and temperature dependent study of the dHvA
effect we determine the electronic structure and demonstrate that the electron
masses are very light, m^* is approximately equalt to 1.2 m_e. The Fermi
surface we observe is essentially that expected of nearly-free electrons -
establishing
Ag5Pb2O6 as the first known example of a monovalent, nearly-free electron
superconductor at ambient pressure.Comment: 4 pages, 3 figure
Fermiology and electronic homogeneity of the superconducting overdoped cuprate Tl-2201 revealed by quantum oscillations
We report an angular quantum oscillation study of Tl_2Ba_2CuO_{6+delta} for
two different doping levels (Tc = 10K and 26 K) and determine the Fermi surface
size and topology in considerable detail. Our results show that Fermi liquid
behavior is not confined to the edge of the superconducting dome and is robust
up to at least T_c^{max}/3.5. Superconductivity is found to survive up to a
larger doping p_c = 0.31 than in La_{2-x}Sr_xCuO_4. Our data imply that
electronic inhomogeneity does not play a significant role in the loss of
superconductivity and superfluid density in overdoped cuprates, and point
towards a purely magnetic or electronic pairing mechanismComment: 4 page
Electric Field Modulation of Galvanomagnetic Properties of Mesoscopic Graphite
Electric field effect devices based on mesoscopic graphite are fabricated for
galvanomagnetic measurements. Strong modulation of magneto-resistance and Hall
resistance as a function of gate voltage is observed as sample thickness
approaches the screening length. Electric field dependent Landau level
formation is detected from Shubnikov de Haas oscillations in
magneto-resistance. The effective mass of electron and hole carriers has been
measured from the temperature dependant behavior of these oscillations.Comment: 4 pages, 4 figures included, submitted to Phys. Rev. Let
Fermi Surface of Alpha-Uranium at Ambient Pressure
We have performed de Haas-van Alphen measurements of the Fermi surface of
alpha-uranium single crystals at ambient pressure within the alpha-3 charge
density wave (CDW) state from 0.020 K - 10 K and magnetic fields to 35 T using
torque magnetometry. The angular dependence of the resulting frequencies is
described. Effective masses were measured and the Dingle temperature was
determined to be 0.74 K +/- 0.04 K. The observation of quantum oscillations
within the alpha-3 CDW state gives new insight into the effect of the charge
density waves on the Fermi surface. In addition we observed no signature of
superconductivity in either transport or magnetization down to 0.020 K
indicating the possibility of a pressure-induced quantum critical point that
separates the superconducting dome from the normal CDW phase.Comment: 11 pages, 4 figures, 3 table
- …