14 research outputs found
STM/STS Study on 4a X 4a Electronic Charge Order and Inhomogeneous Pairing Gap in Superconducting Bi2Sr2CaCu2O8+d
We performed STM/STS measurements on underdoped Bi2212 crystals with doping
levels p ~ 0.11, ~ 0.13 and ~ 0.14 to examine the nature of the nondispersive
4a X 4a charge order in the superconducting state at T << Tc. The charge order
appears conspicuously within the pairing gap, and low doping tends to favor the
charge order. We point out the possibility that the 4a X 4a charge order will
be dynamical in itself, and pinned down over regions with effective pinning
centers. The pinned 4a X 4a charge order is closely related to the spatially
inhomogeneous pairing gap structure, which has often been reported in STS
measurements on high-Tc cuprates.Comment: 12 pages, 16 figures, to be published in Phys. Rev.
Superconducting Properties of MgCNi3 Films
We report the magnetotransport properties of thin polycrystalline films of
the recently discovered non-oxide perovskite superconductor MgCNi3. CNi3
precursor films were deposited onto sapphire substrates and subsequently
exposed to Mg vapor at 700 C. We report transition temperatures (Tc) and
critical field values (Hc2) of MgCNi3 films ranging in thickness from 7.5 nm to
100 nm. Films thicker than ~40 nm have a Tc ~ 8 K, and an upper critical field
Hc2 ~ 14 T, which are both comparable to that of polycrystalline powders. Hall
measurements in the normal state give a carrier density, n =-4.2 x 10^22 cm^-3,
that is approximately 4 times that reported for bulk samples.Comment: submitted to PR
Occurrence of Fermi Pockets without Pseudogap Hypothesis and Clarification of the Energy Distribution Curves of Angle-Resolved Photoemission Spectroscopy in Underdoped Cuprate Superconductors
Central issues in the electronic structure of underdoped cuprate
superconductors are to clarify the shape of the Fermi surfaces and the origin
of the pseudogap. On the basis of the model proposed by Kamimura and Suwa,
which bears important features originating from the interplay of Jahn-Teller
physics and Mott physics, the feature of Fermi surfaces in underdoped cuprates
is the presence of Fermi pockets constructed from doped holes under the
coexistence of a metallic state and a local antiferromagnetic order. Below
, the holes on Fermi pockets form Cooper pairs with d-wave symmetry
in the nodal region. In the antinodal region, there are no Fermi surfaces. In
this study we calculate the energy distribution curves (EDCs) of angle-resolved
photoemission spectroscopy (ARPES) below . It is shown that the
feature of ARPES profiles of underdoped cuprates consists of a coherent peak in
the nodal region and real transitions of photoexcited electrons from occupied
states below the Fermi level to a free-electron state above the vacuum level in
the antinodal region, where the latter transitions form a broad hump. From this
feature, the origin of the two distinct gaps observed by ARPES is elucidated
without introducing the concept of the pseudogap. Finally, a remark is made on
the phase diagram of underdoped cuprates.Comment: arXiv admin note: significant text overlap with arXiv:1006.058
Common ABO variants evaluated and phenotype and related information.
<p>Common ABO variants evaluated and phenotype and related information.</p