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排序方式: 共有78条查询结果,搜索用时 8 毫秒
1.
Ennio Arimondo 《量子光学学报》2006,12(B08):59-60
Cold atoms and, more recently, Bose-Einstein condensates (BEC's) in optical lattices have attracted increasing interest since their first realization. In particular, the formal similarity between the wavefunction of a BEC inside the periodic potential of an optical lattice and of the electrons in a crystal lattice has triggered theoretical and experimental efforts alike. Many phenomena from condensed matter physics, such as Bloch oscillations and Landau-Zener tunneling have been shown to be observable also in optical lattices. An important difference between electrons in a crystal lattice and a BEC inside the periodic potential of an optical lattice is the strength of the self interaction and hence the magnitude of the nonlinearity of the system. Electrons in a metal are almost noninteracting, whereas atoms inside a BEC interact strongly. A' perturbation approach is appropriate in the former case while in the latter the full nonlinearity must be taken into account. From this feature new physics is expected. Most experiments to date have been carried out in the regime of shallow lattice depth, for which the system is well described by the mean field Gross-Pitaevskii equation with a periodic potential. Moreover, the nonlinearity induced by the mean-field of the condensate has been shown, both theoretically and experimentally, to give rise to instabilities in certain regions of the Brillouin zone. These instabilities are not present in the corresponding linear system, i.e. the electron system. Experimental and theoretical results on the subject of nonlinear Landau-Zener tunneling and nonlinearity-induced instabilities in a Bose-Einstein condensate interacting with an external periodic potential will be presented. 相似文献
2.
3.
Simultaneous observations of the optogalvanic and optoacoustic effects were performed in CO2, NH3 and SF6 discharges under irradiation by resonant infrared 10 μm laser radiation. The dependence of the galvanic and acoustic signals on the discharge current, and their time evolution following a switch of the laser radiation were investigated. The observations proved that the infrared optogalvanic effect occurs through two different mechanisms, a gas kinetic temperature dependence of the discharge parameters and a modification of the pion production through the vibrational molecular excitation. 相似文献
4.
We have developed an apparatus for nanostructure fabrication based on direct deposition of laser-manipulated cesium vapors onto pyrolitic graphite. Key features of our apparatus are production and manipulation of a longitudinally cooled atom beam, which allows for straightforward operation in the moderate to low flux density conditions. Both unstructured and structured low surface coverage depositions have been carried out and samples carefully analyzed at the atom scale by in situ tunneling microscopy. Results represent a step forward to the realization of a novel technology for space-controlled deposition of few, eventually single, atoms. 相似文献
5.
An optical atomic clock scheme is proposed that utilizes two lasers to establish coherent coupling between the 5s2 1S0 ground state of 88Sr and the first excited state, 5s5p 3P0. The coupling is mediated by the broad 5s5p 1P1 state, exploiting the phenomenon of electromagnetically induced transparency. The effective linewidth of the clock transition can be chosen at will by adjusting the laser intensity. By trapping the 88Sr atoms in an optical lattice, long interaction times with the two lasers are ensured; Doppler and recoil effects are eliminated. Based on a careful analysis of systematic errors, a clock accuracy of better than 2 x 10(-17) is expected. 相似文献
6.
A.?Camposeo A.?Fioretti F.?Tantussi S.?Gozzini E.?Arimondo C.?GabbaniniEmail author 《Applied physics. B, Lasers and optics》2004,79(5):539-542
Self assembled monolayers (SAM) formed from nonanethiols on thin gold films were exposed to a beam of ground state and metastable neutral barium atoms through a nickel mask. The interaction of the Ba atoms with the nonanethiol layer, followed by an etching process, creates well defined structures on the gold film, with features below 100 nm. We compared the interaction of ground state Ba atoms and SAM molecules with respect to metastable Ba atoms, finding that by using metastable atoms the Ba dose per SAM molecule is reduced. The results indicate that nanofabrication in the nanometer range with barium atoms is feasible. PACS 07.77.Gx; 42.82.Cr; 81.16.Ta 相似文献
7.
Pulsed laser deposition of NiTi shape memory effect thin films 总被引:1,自引:0,他引:1
F. Ciabattari F. Fuso E. Arimondo 《Applied Physics A: Materials Science & Processing》1997,64(6):623-626
2 O3(100) substrates. We also produced free-standing NiTi films by deposition on KBr substrates and subsequent substrate removal
by immersion in water. The presence of the solid-solid phase transformation responsible for the shape memory effect has been
demonstrated through temperature-dependent X-ray diffraction and four-probe resistance versus temperature measurements. On
cooling the deposited film, the austenite-martensite transformation was measured at around 195 K; on heating the film the
reverse transformation was around 250 K. Evidence of the shape-memory effect for free-standing films was obtained in a bending
deformation-shape recovery experiment.
Received: 31 July 1996/Accepted: 6 January 1997 相似文献
8.
Viteau M Bason MG Radogostowicz J Malossi N Ciampini D Morsch O Arimondo E 《Physical review letters》2011,107(6):060402
We experimentally realize Rydberg excitations in Bose-Einstein condensates of rubidium atoms loaded into quasi-one-dimensional traps and in optical lattices. Our results for condensates expanded to different sizes in the one-dimensional trap agree well with the intuitive picture of a chain of Rydberg excitations. We also find that the Rydberg excitations in the optical lattice do not destroy the phase coherence of the condensate, and our results in that system agree with the picture of localized collective Rydberg excitations including nearest-neighbor blockade. 相似文献
9.
Jona-Lasinio M Morsch O Cristiani M Malossi N Müller JH Courtade E Anderlini M Arimondo E 《Physical review letters》2003,91(23):230406
Using a simple model for nonlinear Landau-Zener tunneling between two energy bands of a Bose-Einstein condensate in a periodic potential, we find that the tunneling rates for the two directions of tunneling are not the same. Tunneling from the ground state to the excited state is enhanced by the nonlinearity, whereas in the opposite direction it is suppressed. These findings are confirmed by numerical simulations of the condensate dynamics. Measuring the tunneling rates for a condensate of rubidium atoms in an optical lattice, we have found experimental evidence for this asymmetry. 相似文献
10.
D. Ciampini E. Courtade C. Sias D. Cossart G. Carelli F. Mango O. Morsch E. Arimondo 《Optics Communications》2006,257(2):340-348
We used microwave radiation to evaporatively cool a mixture of of 133Cs and 87Rb atoms in a magnetic trap. A mixture composed of an equal number (around 104) of Rb and Cs atoms in their doubly polarized states at ultracold temperatures was prepared. We also used microwaves to selectively evaporate atoms in different Zeeman states. 相似文献