Time evolution of condensed state of interacting bosons with reduced number fluctuation in a leaky box

We study the time evolution of the Bose-Einstein condensate of interacting bosons confined in a leaky box, when its number fluctuation is initially (t=0) suppressed. We take account of quantum fluctuations of all modes, including k = 0. We identify a ``natural coordinate'' b_0 of the interacting bosons, by which many physical properties can be simply described. Using b_0, we successfully define the cosine and sine operators for interacting many bosons. The wavefunction, which we call the ``number state of interacting bosons'' (NSIB), of the ground state that has a definite number N of interacting bosons can be represented simply as a number state of b_0. We evaluate the time evolution of the reduced density operator \rho(t) of the bosons in the box with a finite leakage flux J, in the early time stage for which Jt << N. It is shown that \rho(t) evolves from a single NSIB at t = 0, into a classical mixture of NSIBs of various values of N at t > 0. We define a new state called the ``number-phase squeezed state of interacting bosons'' (NPIB). It is shown that \rho(t) for t>0 can be rewritten as the phase-randomized mixture (PRM) of NPIBs. It is also shown that the off-diagonal long-range order (ODLRO) and the order parameter defined by it do not distinguish the NSIB and NPIB. On the other hand, the other order parameter \Psi, defined as the expectation value of the boson operator, has different values among these states. For each element of the PRM of NPIBs, we show that \Psi evolves from zero to a finite value very quickly. Namely, after the leakage of only two or three bosons, each element acquires a full, stable and definite (non-fluctuating) value of \Psi.Comment: 25 pages including 3 figures. To appear in Phys. Rev. A (1999). The title is changed to stress the time evolution. Sections II, III and IV of the previous manuscript have been combined into one section. The introduction and summary of the previous manuscript have been combined into the Introduction and Summary. The names and abbreviations of quantum states are changed to stress that they are for interacting many bosons. More references are cite

Low temperature calorimetry and transmission electron microscopy of helium bubbles in Cu

Helium has been introduced into 100 $\mu$m thick pure Cu specimens by implantation of $\alpha$-particles at T = 300 K. Post-implantation annealing of the specimens at high temperatures caused helium to precipitate into bubbles. We have measured the low-temperature heat capacity of helium confined in bubbles of average radius of less than 100 $\mathring{A}$. The size of the bubbles was obtained by transmission electron microscope investigations. We have observed that helium liquifies at low temperatures and undergoes the transition to the superfluid state in bubbles of average radius larger than 35 $\mathring{A}$. Strong modification of supefluidity of helium in bubbles has been observed. It is attributed to the effective confinement of helium in such microscopic bubbles. Thetemperature of the transition to the superfluid state is discussed in terms of the Ginzburg-Pitaevskii-Mamaladze mean field model. To calculate thermodynamic parameters of helium in bubbles we have used an EOS for "superdense" helium in bubbles, whose prediction is found to be in good agreement to our calorimetric observations. The confining geometry of bubbles is $\underline{new}$ and possesses unique features for investigations of confined helium. It provides the possibility to study properties of extremely small, spherical, completely isolated Bose "particles" consisting of 10$^{4}$ helium atoms each. Furthermore, as we show, it can be known with better accuracy than formerly investigated confining geometries

Unusual magnetic properties of LaMnO3+δ

DC magnetization measurements on polycrystalline LaMnO3+δ at different cooling rates have shown a remarkably unusual temperature dependence. The difference of MZFC(T) observed for slow and fast cooling experiments might be attributed to different magnetic states frozen in the sample at temperatures around TN. Based on the similarity between the MFC(T) of the YVO3+δ compound and the MZFC (T) of fast cooled LaMnO3+δ specimen, the observed behavior might be attributed to the Dzyaloshinsky-Moriya interaction. © 2003 Elsevier B.V. All rights reserved

Synthesis of magnetocaloric Mn5-xFexSi3 (2.5≤x≤4.0) compounds and the influence of various sintering atmospheres on the magnetic and electrical properties

Polycrystalline powders of Mn5-xFexSi3 (x ​= ​2.5, 3.0, 3.5, 4.0) compounds (Mn5Si3-type, space group P63/mcm, No. 193) were prepared by solid state reaction of pure Mn, Fe and Si powders under High Vacuum (HV) conditions at T ​= ​1000 ​°C. Samples were sintered at T ​= ​1100 ​°C under HV as well as under Ar-4%H2 conditions. X-ray Diffraction (XRD) analysis revealed that the compounds crystallize with hexagonal symmetry in accordance with previous reports. The χac susceptibility measurements for the samples sintered under HV conditions show systematic strengthening of the ferromagnetic (FM) state upon increasing x. The electrical resistivity, ρ, remains metallic for all x, with a very weak temperature dependence at T ​&amp;gt; ​300 ​K. At T ​&amp;lt; ​300 ​K, ρ(T) shows a linear temperature dependence with a change of slope observed upon approaching the corresponding magnetic ordering temperature. For the samples sintered under flowing Ar-4%H2 atmosphere, the electrical properties are similar to those of the samples sintered under HV, while a strong enhancement of χac was observed. © 2021 Elsevier Inc

Low-temperature transport properties of non-stoichiometric La0.95-xSrxMnO3 manganites

The low-temperature specific heat and electrical resistivity of the polycrystalline non-stoichiometric manganites La0.95-xSrxMnO3 have been investigated in the doping region x = 0.00-0.30. The specific heat has terms proportional to T and T3. The resistivity of the samples decreases as T1/2 with increasing temperature, goes through a minimum and then increases proportionally to T3. The temperature Train, corresponding to the minimum of the resistivity, shifts with Sr content as Tmin ∼ x-2/5

Structural and high temperature electrical properties of Lay-xSrxMnO3 perovskite materials

The phase constitution of Lay-xSrxMnO3 perovskite materials with [MATH] and [MATH] prepared by wet chemical techniques has been determined. Single phase La-deficient materials have been obtained at y=0.95 and [MATH] as well as for [MATH] and [MATH]. The observed variation of the lattice parameters leads to shrinking unit cell volume with Sr-content and with La-deficiency. Small polaron conduction has been observed for [MATH], while for [MATH] metallic-like behaviour is observed for La-deficient materials. The electrical conductivity of Sr-free materials at 950 °C approaches 100 S/cm. The activation energy for conduction changes strongly with sintering temperature and composition of the specimen

VO2 thin films fabricated by reduction of thermal evaporated V2O5 under N2 flow

VO2 thin films were fabricated by thermal evaporation of V2O5 on quartz and glass and subsequent reduction in nitrogen (N2). This Physical Vapor Deposition (PVD) method resulted in high-quality single phase VO2(M1) films with sharp changes in resistance (3–4 orders of magnitude) and transmittance (40–45%) at λ= 1550 nm accompanied by narrow hysteresis loops (~ 4–5 K) around the Semiconductor-to-Metal Transition (SMT). © 2021 Elsevier B.V