J. Keller
YOU?
Author Swipe
View article: Radio-frequency-induced ground-state degeneracy in a Bose-Einstein condensate of chromium atoms
Radio-frequency-induced ground-state degeneracy in a Bose-Einstein condensate of chromium atoms Open
We study the effect of strong radio-frequency (rf) fields on a chromium Bose-Einstein condensate (BEC), in a regime where the rf frequency is much larger than the Larmor frequency. We use the modification of the Land\'{e} factor by the rf …
View article: Radio-frequency induced ground state degeneracy in a Chromium Bose-Einstein condensate
Radio-frequency induced ground state degeneracy in a Chromium Bose-Einstein condensate Open
We study the effect of strong radio-frequency (rf) fields on a chromium Bose-Einstein condensate (BEC), in a regime where the rf frequency is much larger than the Larmor frequency. We use the modification of the Landé factor by the rf fiel…
View article: Radio-frequency control of the Lande factor of Bose-condensed chromium atoms
Radio-frequency control of the Lande factor of Bose-condensed chromium atoms Open
We study the effect of strong radio-frequency (rf) fields on a chromium Bose-Einstein condensate, in a regime where the rf frequency is much larger than the Larmor frequency. We show that the Lande factor of the atoms is lowered by the pre…
View article: All-optical production of chromium Bose-Einstein condensates
All-optical production of chromium Bose-Einstein condensates Open
We report on the production of ^52Cr Bose Einstein Condensates (BEC) with an all-optical method. We first load 5.10^6 metastable chromium atoms in a 1D far-off-resonance optical trap (FORT) from a Magneto Optical Trap (MOT), by combining t…
View article: Averaging out magnetic forces with fast rf sweeps in an optical trap for metastable chromium atoms
Averaging out magnetic forces with fast rf sweeps in an optical trap for metastable chromium atoms Open
We introduce a novel type of time-averaged trap, in which the internal state of the atoms is rapidly modulated to modify magnetic trapping potentials. In our experiment, fast radiofrequency (rf) linear sweeps flip the spin of atoms at a fa…
View article: Accumulation and thermalization of cold atoms in a finite-depth magnetic trap
Accumulation and thermalization of cold atoms in a finite-depth magnetic trap Open
We experimentally and theoretically study the continuous accumulation of cold atoms from a magneto-optical trap (MOT) into a finite depth trap, consisting in a magnetic quadrupole trap dressed by a radiofrequency (RF) field. Chromium atoms…
View article: Simultaneous magneto-optical trapping of bosonic and fermionic chromium atoms
Simultaneous magneto-optical trapping of bosonic and fermionic chromium atoms Open
We report on magneto-optical trapping of fermionic 53Cr atoms. A Zeeman-slowed atomic beam provides loading rates up to 3 10^6 /s. We present systematic characterization of the magneto-optical trap (MOT). We obtain up to 5 10^5 atoms in th…
View article: Inelastic resonant tunneling through single molecules and quantum dots: Spectrum modification due to nonequilibrium effects
Inelastic resonant tunneling through single molecules and quantum dots: Spectrum modification due to nonequilibrium effects Open
Resonant electron transport through a mesoscopic region (quantum dot or\nsingle molecule) with electron-phonon interaction is considered at finite\nvoltage. In this case the standard Landauer-B\\"uttiker approach cannot be\napplied. Using …
View article: Static charge-imbalance effects in intrinsic Josephson systems
Static charge-imbalance effects in intrinsic Josephson systems Open
Nonequilibrium effects created by stationary current injection in layered\nd-wave superconductors forming a stack of intrinsic Josephson junctions are\nstudied. Starting from a nonequilibrium Green function theory we derive\nmicroscopic ex…
View article: Thermal fluctuations in ultrasmall intrinsic Josephson junctions
Thermal fluctuations in ultrasmall intrinsic Josephson junctions Open
Current-voltage curves of small area hysteretic intrinsic Josephson\njunctions, for which the Josephson energy $E_J=\\hbar J_c/2e$ is of order of\nthermal energy $kT$, are investigated. A non-monotonic temperature dependence\nof the switch…
View article: Superlattice with hot electron injection: An approach to a Bloch oscillator
Superlattice with hot electron injection: An approach to a Bloch oscillator Open
A semiconductor superlattice with hot electron injection into the miniband is\nconsidered. The injection changes the stationary distribution function and\nresults in a qualitative change of the frequency behaviour of the differential\ncond…
View article: Non-equilibrium effects due to charge fluctuations in intrinsic Josephson systems
Non-equilibrium effects due to charge fluctuations in intrinsic Josephson systems Open
Nonequilibrium effects in layered superconductors forming a stack of\nintrinsic Josephson junctions are investigated. We discuss two basic\nnonequilibrium effects caused by charge fluctuations on the superconducting\nlayers: a) the shift o…
View article: <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="italic">d</mml:mi></mml:math>-Wave Superconductivity in the Hubbard Model
-Wave Superconductivity in the Hubbard Model Open
The superconducting instabilities of the doped repulsive 2D Hubbard model are studied in the intermediate to strong coupling regime with the help of the dynamical cluster approximation. To solve the effective cluster problem we employ an e…
View article: LDA+DMFT study for $La_{1-x}Sr_{x}TiO_{3}$
LDA+DMFT study for $La_{1-x}Sr_{x}TiO_{3}$ Open
The dynamical mean-field theory together with the non-crossing approximation is used to set up a novel scheme to study the electronic structure of strongly correlated electron systems. The non-interacting band structure is obtained from a …
View article: Collective modes in the electronic polarization of double-layer systems in the superconducting state
Collective modes in the electronic polarization of double-layer systems in the superconducting state Open
Standard weak coupling methods are used to study collective modes in the\nsuperconducting state of a double-layer system with intralayer and interlayer\ninteraction, as well as a Josephson-type coupling and single particle hopping\nbetween…
View article: Interaction of three-level atoms with stochastic fields
Interaction of three-level atoms with stochastic fields Open
laser pulses are used to drive transitions between three levels in Sr vapor.
View article: INHOMOGENEOUS DEPHASING INHIBITION BY A STRONG STOCHASTIC FIELD
INHOMOGENEOUS DEPHASING INHIBITION BY A STRONG STOCHASTIC FIELD Open
We examine the formation of coherent transient optical signals produced by the rephasing of dipoles which are built up by a strong broadband light pulse. The inhibition of inhomogeneous dephasing by a strong stochastic field is predicted w…
View article: Investigation of elastic and depolarizing collisions in strontium using broadband stimulated photon echoes
Investigation of elastic and depolarizing collisions in strontium using broadband stimulated photon echoes Open
Elastic and depolarizing collisions between excited strontium (5s5p 3 P 1 ) and noble gases are investigated in a broadband stimulated photon echo (SPE) experiment. The stimulated photon echo signal produced under broadband (incoherent) e…
View article: COLLISIONAL IONIZATION IN A RESONANTLY EXCITED ATOMIC VAPOR
COLLISIONAL IONIZATION IN A RESONANTLY EXCITED ATOMIC VAPOR Open
Collisional ionization of sodium and barium vapors resonantly excited with c.w. or pulsed laser sources, and subsequent electron-atom energy transfers, are studied by electron spectroscopy. Cross sections for associative and Penning ioniza…
View article: Observation of Ionization of Laser Excited Atoms by Synchrotron Radiation
Observation of Ionization of Laser Excited Atoms by Synchrotron Radiation Open
We have begun a program to measure oscillator strengths of autoionizing resonances that result from a transition in the VUV between a laser excited initial state and a final state in which a core electron is promoted. These measurements de…
View article: Investigation of the dynamic Stark effect of a J = 0 ↔ J = 1 optical transition
Investigation of the dynamic Stark effect of a J = 0 ↔ J = 1 optical transition Open
The dynamic Stark effect (Autler-Townes splitting and radiative shift) of a J = 0 ↔ J = 1 optical transition have been investigated. The barium atomic beam is illuminated by a strong pump beam, resonant or slightly non-resonant with the Ba…
View article: The optical autler-townes effect in doppler-broadened three-level systems
The optical autler-townes effect in doppler-broadened three-level systems Open
2014 Some features of the optical Autler-Townes effect as observed in Doppler-broadened three-level systems, including the physical significance of the observed line splitting, the conditions for the observation of the doublet, the doublet…
View article: Shell model investigation of the Raman scattering in the ordered and disordered phases of NH4Br
Shell model investigation of the Raman scattering in the ordered and disordered phases of NH4Br Open
We describe a formalism for the Raman scattering from orientationally disordered solids, in particular for the ammonium halides. The electronic polarizability is treated in a shell model. Applying the theory to the ordered phase of NH4Br w…
View article: ELECTRONIC STRUCTURE OF LIQUID TRANSITION AND RARE-EARTH METALS AND THEIR ALLOYS
ELECTRONIC STRUCTURE OF LIQUID TRANSITION AND RARE-EARTH METALS AND THEIR ALLOYS Open
The recent progress in the experimental work on liquid transition and rare earth metals and their alloys is reviewed. The results are compared with recent theories taking into account the 3d, 4f and 5d states, respectively.