22,893 research outputs found
Extent of Fermi-surface reconstruction in the high-temperature superconductor HgBaCuO
High magnetic fields have revealed a surprisingly small Fermi-surface in
underdoped cuprates, possibly resulting from Fermi-surface reconstruction due
to an order parameter that breaks translational symmetry of the crystal
lattice. A crucial issue concerns the doping extent of this state and its
relationship to the principal pseudogap and superconducting phases. We employ
pulsed magnetic field measurements on the cuprate HgBaCuO to
identify signatures of Fermi surface reconstruction from a sign change of the
Hall effect and a peak in the temperature-dependent planar resistivity. We
trace the termination of Fermi-surface reconstruction to two hole
concentrations where the superconducting upper critical fields are found to be
enhanced. One of these points is associated with the pseudogap end-point near
optimal doping. These results connect the Fermi-surface reconstruction to both
superconductivity and the pseudogap phenomena.Comment: 5 pages. 3 Figures. PNAS (2020
Surface reconstruction induced geometries of Si clusters
We discuss a generalization of the surface reconstruction arguments for the
structure of intermediate size Si clusters, which leads to model geometries for
the sizes 33, 39 (two isomers), 45 (two isomers), 49 (two isomers), 57 and 61
(two isomers). The common feature in all these models is a structure that
closely resembles the most stable reconstruction of Si surfaces, surrounding a
core of bulk-like tetrahedrally bonded atoms. We investigate the energetics and
the electronic structure of these models through first-principles density
functional theory calculations. These models may be useful in understanding
experimental results on the reactivity of Si clusters and their shape as
inferred from mobility measurements.Comment: 9 figures (available from the author upon request) Submitted to Phys.
Rev.
Fermi Surface Reconstruction by Dynamic Magnetic Fluctuations
We demonstrate that nearly critical quantum magnetic fluctuations in strongly
correlated electron systems can change the Fermi surface topology and also lead
to spin charge separation (SCS) in two dimensions. To demonstrate these effects
we consider a small number of holes injected into the bilayer antiferromagnet.
The system has a quantum critical point (QCP) which separates magnetically
ordered and disordered phases. We demonstrate that in the physically
interesting regime there is a magnetically driven Lifshitz point (LP) inside
the magnetically disordered phase. At the LP the topology of the hole Fermi
surface is changed. We also demonstrate that in this regime the hole spin and
charge necessarily separate when approaching the QCP. The considered model
sheds light on generic problems concerning the physics of the cuprates.Comment: updated version, accepted to PR
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