586 research outputs found
A Phase Change Memory Chip Based on TiSbTe Alloy in 40-nm Standard CMOS Technology
In this letter, a phase change random access memory (PCRAM) chip based on Ti0.4Sb2Te3 alloy material was fabricated in a 40-nm 4-metal level complementary metal-oxide semiconductor (CMOS) technology. The phase change resistor was then integrated after CMOS logic fabrication. The PCRAM was successfully embedded without changing any logic device and process, in which 1.1 V negative-channel metal-oxide semiconductor device was used as the memory cell selector. The currents and the time of SET and RESET operations were found to be 0.2 and 0.5 mA, 100 and 10 ns, respectively. The high speed performance of this chip may highlight the design advantages in many embedded applications
Interplay between multiple charge-density waves and the relationship with superconductivity in PdHoTe
HoTe, a member of the rare-earth tritelluride (Te) family, and
its Pd-intercalated compounds, PdHoTe, where superconductivity (SC)
sets in as the charge-density wave (CDW) transition is suppressed by the
intercalation of a small amount of Pd, are investigated using angle-resolved
photoemission spectroscopy (ARPES) and electrical resistivity. Two
incommensurate CDWs with perpendicular nesting vectors are observed in
HoTe at low temperatures. With a slight Pd intercalation ( = 0.01),
the large CDW gap decreases and the small one increases. The momentum
dependence of the gaps along the inner Fermi surface (FS) evolves from
orthorhombicity to near tetragonality, manifesting the competition between two
CDW orders. At = 0.02, both CDW gaps decreases with the emergence of SC.
Further increasing the content of Pd for = 0.04 will completely suppress
the CDW instabilities and give rise to the maximal SC order. The evolution of
the electronic structures and electron-phonon couplings (EPCs) of the multiple
CDWs upon Pd intercalation are carefully scrutinized. We discuss the interplay
between multiple CDW orders, and the competition between CDW and SC in detail.Comment: 6 pages, 5 figure
muSR and Magnetometry Study of the Type-I Superconductor BeAu
We present muon spin rotation and relaxation (muSR) measurements as well as
demagnetising field corrected magnetisation measurements on polycrystalline
samples of the noncentrosymmetric superconductor BeAu. From muSR measurements
in a transverse field, we determine that BeAu is a type-I superconductor with
Hc = 256 Oe, amending the previous understanding of the compound as a type-II
superconductor. To account for demagnetising effects in magnetisation
measurements, we produce an ellipsoidal sample, for which a demagnetisation
factor can be calculated. After correcting for demagnetising effects, our
magnetisation results are in agreement with our muSR measurements. Using both
types of measurements we construct a phase diagram from T = 30 mK to Tc = 3.25
K. We then study the effect of hydrostatic pressure and find that 450 MPa
decreases Tc by 34 mK, comparable to the change seen in type-I elemental
superconductors Sn, In and Ta, suggesting BeAu is far from a quantum critical
point accessible by the application of pressure.Comment: 10 pages, 8 figure
Disentangling superconducting and magnetic orders in NaFe_1-xNi_xAs using muon spin rotation
Muon spin rotation and relaxation studies have been performed on a "111"
family of iron-based superconductors NaFe_1-xNi_xAs. Static magnetic order was
characterized by obtaining the temperature and doping dependences of the local
ordered magnetic moment size and the volume fraction of the magnetically
ordered regions. For x = 0 and 0.4 %, a transition to a nearly-homogeneous long
range magnetically ordered state is observed, while for higher x than 0.4 %
magnetic order becomes more disordered and is completely suppressed for x = 1.5
%. The magnetic volume fraction continuously decreases with increasing x. The
combination of magnetic and superconducting volumes implies that a
spatially-overlapping coexistence of magnetism and superconductivity spans a
large region of the T-x phase diagram for NaFe_1-xNi_xAs . A strong reduction
of both the ordered moment size and the volume fraction is observed below the
superconducting T_C for x = 0.6, 1.0, and 1.3 %, in contrast to other iron
pnictides in which one of these two parameters exhibits a reduction below TC,
but not both. The suppression of magnetic order is further enhanced with
increased Ni doping, leading to a reentrant non-magnetic state below T_C for x
= 1.3 %. The reentrant behavior indicates an interplay between
antiferromagnetism and superconductivity involving competition for the same
electrons. These observations are consistent with the sign-changing s-wave
superconducting state, which is expected to appear on the verge of microscopic
coexistence and phase separation with magnetism. We also present a universal
linear relationship between the local ordered moment size and the
antiferromagnetic ordering temperature TN across a variety of iron-based
superconductors. We argue that this linear relationship is consistent with an
itinerant-electron approach, in which Fermi surface nesting drives
antiferromagnetic ordering.Comment: 20 pages, 14 figures, Correspondence should be addressed to Prof.
Yasutomo Uemura: [email protected]
Discovery of Superconductivity and Electron-Phonon Drag in the Non-Centrosymmetric Semimetal LaRhGe
We present a comprehensive study of the non-centrosymmetric semimetal
LaRhGe. Our transport measurements reveal evidence for electron-hole
compensation at low temperatures, resulting in a large magnetoresistance of
3000% at 1.8 K and 14 T. The carrier concentration is on the order of
, higher than typical semimetals. We predict theoretically
the existence of Weyl nodal lines that are protected
by the tetragonal space group. We discover superconductivity for the first time
in this compound with a of 0.39(1) K and of
2.1(1) mT, with evidence from specific heat and transverse-field muon spin
relaxation (). LaRhGe is a weakly-coupled type-I
superconductor, and we find no evidence for time-reversal symmetry breaking in
our zero-field . We study the electrical transport in the normal
state and find an unusual dependence at low temperature while
Seebeck coefficient and thermal conductivity measurements reveal a peak in the
same temperature range. We conclude that the transport properties of LaRhGe
in its normal state are strongly influenced by electron-phonon interactions.
Furthermore, we examine the temperature dependent Raman spectra of LaRhGe
and find that the lifetime of the lowest energy phonon is dominated by
phonon-electron scattering instead of anharmonic decay
Enhanced polarization and abnormal flexural deformation in bent freestanding perovskite oxides
Recent realizations of ultrathin freestanding perovskite oxides offer a unique platform to probe novel properties in two-dimensional oxides. Here, we observe a giant flexoelectric response in freestanding BiFeO3 and SrTiO3 in their bent state arising from strain gradients up to 3.5 × 107 m−1, suggesting a promising approach for realizing ultra-large polarizations. Additionally, a substantial change in membrane thickness is discovered in bent freestanding BiFeO3, which implies an unusual bending-expansion/shrinkage effect in the ferroelectric membrane that has never been seen before in crystalline materials. Our theoretical model reveals that this unprecedented flexural deformation within the membrane is attributable to a flexoelectricity–piezoelectricity interplay. The finding unveils intriguing nanoscale electromechanical properties and provides guidance for their practical applications in flexible nanoelectromechanical systems
A prognostic index model for assessing the prognosis of ccRCC patients by using the mRNA expression profiles of AIF1L, SERPINC1 and CES1
Background: Kidney carcinoma is a major cause of carcinoma-related
death, with the prognosis for advanced or metastatic renal cell carcinoma still
very poor. The aim of this study was to investigate feasible prognostic
biomarkers that can be used to construct a prognostic index model for clear cell
renal cell carcinoma (ccRCC) patients. Methods: The mRNA expression profiles of ccRCC samples were downloaded
from the The Cancer Genome Atlas (TCGA) dataset and the correlation of
AIF1L with malignancy, tumor stage and prognosis were evaluated.
Differentially expressed genes (DEGs) between AIF1L-low and
AIF1L-high expression groups were selected. Those with prognostic value
as determined by univariate and multivariate Cox regression analysis were then
used to construct a prognostic index model capable of predicting the outcome of
ccRCC patients. Results: The expression level of AIF1L was lower in ccRCC
samples than in normal kidney samples. AIF1L expression showed an
inverse correlation with tumor stage and a positive association with better
prognosis. ccRCC samples were divided into high- and low-expression groups
according to the median value of AIF1L expression. In the
AIF1L-high expression group, 165 up-regulated DEGs and 601
down-regulated DEGs were identified. Three genes (AIF1L,
SERPINC1 and CES1) were selected following univariate and
multivariate Cox regression analysis. The hazard ratio (HR) and 95% confidence
intervals (CI) for these genes were: AIF1L (HR = 0.83, 95% CI:
0.76–0.91), SERPINC1 (HR = 1.33, 95% CI: 1.12–1.58), and
CES1 (HR = 0.87, 95% CI: 0.78–0.97). A prognostic index model based on
the expression level of the three genes showed good performance in predicting
ccRCC patient outcome, with an area under the ROC curve (AUC) of 0.671. Conclusion: This research provides a better understanding of the
correlation between AIF1L expression and ccRCC. We propose a novel
prognostic index model comprising AIF1L, SERPINC1 and
CES1 expression that may assist physicians in determining the prognosis
of ccRCC patients
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