We present an exact quantum Monte Carlo study of the attractive one-dimensional Hubbard model with imbalanced fermion population. The pair-pair correlation function, which decays monotonically in the absence of polarization P, develops oscillations when P is nonzero, characteristic of Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase. The pair momentum distribution peaks at a momentum equal to the difference in the Fermi momenta. At strong coupling, the minority and majority momentum distributions are shown to be deformed, reflecting the presence of the other species and its Fermi surface. The FFLO oscillations survive the presence of a confining potential, and the local polarization at the trap center exhibits a marked dip, similar to that observed experimentally. 相似文献
Using scanning tunneling microscopy (STM) and density functional theory simulations, we have studied the diffusion of alkoxy species formed by the dissociation of alcohols on bridge-bonded oxygen (BBO) vacancies (BBO(V)'s) on TiO2(110). At elevated temperatures (>or=400 K) the sequential isothermal STM images show that mobile BBO(V)'s mediate the diffusion of alkoxy species by providing space for alkyl-group-bearing BBO atom to diffuse into. The experimental findings are further supported by simulations that find that BBO(V) diffusion is the rate limiting step in the overall diffusion mechanism. 相似文献
In the past few decades, several models have predicted an energy dependence of the speed of light in the context of quantum gravity. For cosmological sources such as active galaxies, this minuscule effect can add up to measurable photon-energy dependent time lags. In this Letter a search for such time lags during the High Energy Stereoscopic System observations of the exceptional very high energy flare of the active galaxy PKS 2155-304 on 28 July 2006 is presented. Since no significant time lag is found, lower limits on the energy scale of speed of light modifications are derived. 相似文献
Within the last decade mid-infrared absorption spectroscopy between 3 and 20 μm, known as infrared laser absorption spectroscopy
(IRLAS) and based on tuneable semiconductor lasers, namely lead salt diode lasers, often called tuneable diode lasers (TDL),
and quantum cascade lasers (QCL) has progressed considerably as a powerful diagnostic technique for in situ studies of the
fundamental physics and chemistry of molecular plasmas. The increasing interest in processing plasmas containing hydrocarbons,
fluorocarbons, organo-silicon and boron compounds has lead to further applications of IRLAS because most of these compounds
and their decomposition products are infrared active. IRLAS provides a means of determining the absolute concentrations of
the ground states of stable and transient molecular species, which is of particular importance for the investigation of reaction
kinetics. Since plasmas with molecular feed gases are used in many applications such as thin film deposition, semiconductor
processing, surface activation and cleaning, and materials and waste treatment, this has stimulated the adaptation of infrared
spectroscopic techniques to industrial requirements. The recent development of QCLs offers an attractive new option for the
monitoring and control of industrial plasma processes as well as for highly time-resolved studies on the kinetics of plasma
processes.
The aim of the present article is twofold: (i) to review recent achievements in our understanding of molecular phenomena in
plasmas using TDLs and (ii) to report on selected new applications of QCLs in the mid-infrared.
PACS 07.57.Ty; 52.70.Kz; 52.80.-s 相似文献
The aim of this paper is to check the effect of artefacts introduced by focused ion beam (FIB) milling on the strain measurement by convergent beam electron diffraction (CBED). We show that on optimized silicon FIB samples, the strain measurement can be performed with a sensitivity of about 2.5 × 10−4 which is very close to the theoretical one and we conclude that FIB preparation can be suitable for such measurements in microelectronic devices.
To achieve this, we first used CBED and electron energy loss spectroscopy (EELS) which provide a procedure permitting an exact knowledge of the sample geometry, i.e. the thickness of both amorphous and crystalline layers. This procedure was used in order to measure the FIB-amorphized sidewall layer. It was found that if the FIB preparation is optimized one can reduce this amorphous layer down to around 7 nm on each side. Secondly different preparation techniques (cleavage, Tripod™ and FIB) permit to check if the surface damaged layer introduced by FIB influences the strain state of the sample. Finally, it was found that the damaged layer does not introduce measurable strain in pure silicon but reduces appreciably the quality of the CBED patterns. 相似文献
This paper determines lower bounds on the number of different cycle lengths in a graph of given minimum degree k and girth g. The most general result gives a lower bound of ckg/8. 相似文献
The 81, 82, 83, 85Se nuclei have been produced as fission fragments in the fusion reaction 18O + 208Pb at 85MeV bombarding energy and studied with the Euroball IV array. Their high-spin level schemes have been built from the
triple -ray coincidence data and - angular correlations have been analyzed in order to assign spin and parity values to many observed states. The lowest-spin
states of the two-neutron and three-neutron configurations are strongly mixed with two-proton excitations among the fp orbits. On the other hand, the highest-spin states of these neutron configurations are found to remain almost pure. Neutron
excitation across the N = 50 gap is observed both in 83Se49 and in 85Se51 . 相似文献
A series of 4,4-difluoroisofagomine analogues were synthesized. These compounds were tested for inhibition of eight glycosidases. The 3R,5R isomer 1 is a new and potent inhibitor against β-glucosidase from almonds with Ki value of 1.2 μM. The influence of the gem-difluoromethylene group (CF2) on binding to glycosidases is discussed. It is concluded that only non-essential hydroxyl groups can be replaced by the gem-difluoro group and that in such a case (β-glycosidase) the change in inhibition is, interestingly, a result of the change in base strength. 相似文献