332 research outputs found
Gender discourse, awareness, and alternative responses for men in everyday living
In this paper, the authors use examples from their experiences to explore the nuances and complexities of contemporary gender practices. They draw on discourse and positioning theories to identify the ways in which culturally dominant, and difficult to notice, gender constructions help shape everyday experiences. In addition, the authors share their view that there are benefits in developing skills in noticing contemporary practices made available by dominant gender constructions. Such noticing expands possibilities for ways of responding and relating that might produce outcomes for men and women that fit with their hopes for living
Fermi-surface topology and the effects of intrinsic disorder in a class of charge-transfer salts containing magnetic ions: ÎČ" â (BEDT â TTF)â [(HâO)M(CâOâ)â]΄ (M = Ga, Cr, Fr; ΄ = Câ Hâ N)
We report high-field magnetotransport measurements on ÎČ" â (BEDT â TTF)â [(HâO)M(CâOâ)â]΄, where M =Ga, Cr and Fe and ΄ = Câ
Hâ
N. We observe similar Shubnikovâde Haas oscillations in all compounds, attributable to four quasi-two-dimensional Fermi-surface pockets, the largest of which corresponds to a cross-sectional area â 8.5% of the Brillouin zone. The cross-sectional areas of the pockets are in agreement with the expectations for a compensated semimetal, and the corresponding effective masses are âŒmâ, rather small compared to those of other BEDT-TTF salts. Apart from the case of the smallest Fermi-surface pocket, varying the M ion seems to have little effect on the overall Fermi-surface topology or on the effective masses. Despite the fact that all samples show quantum oscillations at low temperatures, indicative of Fermi liquid behavior, the sample and temperature dependence of the interlayer resistivity suggest that these systems are intrinsically inhomogeneous. It is thought that intrinsic tendency to disorder in the anions and/or the ethylene groups of the BEDT-TTF molecules leads to the coexistence of insulating and metallic states at low temperatures. A notional phase diagram is given for the general family of ÎČ" â (BEDT â TTF)â [(HâO)M(CâOâ)â]΄ salts
Pressure dependence of the Shubnikov-de Haas oscillation pectrum of beta''-(BEDT-TTF)4(NH4)[Cr(C2O4)3].DMF
The Shubnikov-de Haas (SdH) oscillation spectra of the
beta''-(BEDT-TTF)4(NH4)[Cr(C2O4)\_3].DMF organic metal have been studied in
pulsed magnetic fields of up to either 36 T at ambient pressure or 50 T under
hydrostatic pressures of up to 1 GPa. The ambient pressure SdH oscillation
spectra can be accounted for by up to six fundamental frequencies which points
to a rather complex Fermi surface (FS). A noticeable pressure-induced
modification of the FS topology is evidenced since the number of frequencies
observed in the spectra progressively decreases as the pressure increases.
Above 0.8 GPa, only three compensated orbits are observed, as it is the case
for several other isostructural salts of the same family at ambient pressure.
Contrary to other organic metals, of which the FS can be regarded as a network
of orbits, no frequency combinations are observed for the studied salt, likely
due to high magnetic breakdown gap values or (and) high disorder level
evidenced by Dingle temperatures as large as about 7 K.Comment: To be published in European Physical Journal
Landau quantization effects in the charge-density-wave system (Per)(mnt) (where Au and Pt)
A finite transfer integral orthogonal to the conducting chains of a
highly one-dimensional metal gives rise to empty and filled bands that simulate
an indirect-gap semiconductor upon formation of a commensurate
charge-density-wave (CDW). In contrast to semiconductors such as Ge and Si with
bandgaps eV, the CDW system possesses an indirect gap with a greatly
reduced energy scale, enabling moderate laboratory magnetic fields to have a
major effect. The consequent variation of the thermodynamic gap with magnetic
field due to Zeeman splitting and Landau quantization enables the electronic
bandstructure parameters (transfer integrals, Fermi velocity) to be determined
accurately. These parameters reveal the orbital quantization limit to be
reached at T in (Per)(mnt) salts, making them highly
unlikely candidates for a recently-proposed cascade of field-induced
charge-density wave states
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
Low-Frequency Quantum Oscillations due to Strong Electron Correlations
The normal-state energy spectrum of the two-dimensional - model in a
homogeneous perpendicular magnetic field is investigated. The density of states
at the Fermi level as a function of the inverse magnetic field
reveals oscillations in the range of hole concentrations . The
oscillations have both high- and low-frequency components. The former
components are connected with large Fermi surfaces, while the latter with van
Hove singularities in the Landau subbands, which traverse the Fermi level with
changing . The singularities are related to bending the Landau subbands due
to strong electron correlations. Frequencies of these components are of the
same order of magnitude as quantum oscillation frequencies observed in
underdoped cuprates.Comment: 10 pages, 3 figures, Proc. NSS-2013, Yalta. arXiv admin note: text
overlap with arXiv:1308.056
Multi-flavor quantum criticality
In a quantum critical metal, the electronic density of states, or
quasiparticle mass on the Fermi surface, is strongly enhanced through
electronic correlations. The density of states in the quantum critical
unconventional superconductor CeCoIn, can be readily accessed in the normal
state because all energy scales are small. However, the experimental challenges
associated with large nuclear specific heat and long nuclear spin-lattice
relaxation times have impeded unveiling a more detailed physical picture. Here
we report an extensive thermal impedance spectroscopy study of CeCoIn that
assesses the density of states in two independent ways, via the nuclear
spin-lattice relaxation rate and via the specific heat. We establish that the
temperature- and magnetic field dependence of the nuclear spin-lattice
relaxation rate is determined entirely by the energy-scale competition near the
quantum critical point. In particular, mass enhancement is cut off at finite
magnetic fields. However, the specific heat measurements reveal excess entropy
in addition to that associated with the density of states on the Fermi surface.
This excess entropy is direct thermodynamic evidence for a "second flavor" of
fluctuating boson in CeCoIn. The electronic nature of this excess entropy
is evidenced by its suppression in the superconducting state. We suggest such a
multi-flavour character for a broader class of quantum critical metals.Comment: 39 page
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