arXiv subjects

Sebastian Kling

Publications and source records attributed to Sebastian Kling.

7 recordsLinked to original sources

arXiv2013

Klein-Tunneling of a Quasirelativistic Bose-Einstein Condensate in an Optical Lattice

Optical lattices have proven to be powerful systems for quantum simulations of solid state physics effects. Here we report a proof-of-principle experiment simulating effects predicted by relativistic wave equations with ultracold atoms in a bichromatic optical lattice that allows for a tailoring of the dispersion relation. We observe the analog of Klein-tunneling, the penetration of relativistic particles through a potential barrier without the exponential damping that is characteristic for nonrelativistic quantum tunneling. Both linear (relativistic) and quadratic (nonrelativistic) dispersion relations are investigated, and significant barrier transmission is observed only for the relativistic case.

quant-ph↗

arXiv2011

Atomic Landau-Zener tunneling in Fourier-synthesized optical lattices

We report on an experimental study of quantum transport of atoms in variable periodic optical potentials. The band structure of both ratchet-type asymmetric and symmetric lattice potentials is explored. The variable atom potential is realized by superimposing a conventional standing wave potential of λ/2 spatial periodicity with a fourth-order multiphoton potential of λ/4 periodicity. We find that the Landau-Zener tunneling rate between the first and the second excited Bloch band depends critically on the relative phase between the two spatial lattice harmonics.

cond-mat.other↗

arXiv2010

Atomic Bloch-Zener Oscillations and Stückelberg Interferometry in Optical Lattices

We report on experiments investigating quantum transport and band interferometry of an atomic Bose-Einstein condensate in an optical lattice with a two-band miniband structure, realized with a Fourier-synthesized optical lattice potential. Bloch-Zener oscillations, the coherent superposition of Bloch oscillations and Landau-Zener tunneling between the two bands are observed. When the relative phase between paths in different bands is varied, an interference signal is observed, demonstrating the coherence of the dynamics in the miniband system. Measured fringe patterns of this Stückelberg interferometer allow to interferometrically map out the band structure of the optical lattice over the full Brillouin zone.

cond-mat.quant-gas↗

arXiv2009

Directed Transport of Atoms in a Hamiltonian Quantum Ratchet

We demonstrate the operation of a quantum ratchet in the absence of dissipative processes within the observation time (Hamiltonian regime). An atomic rubidium Bose-Einstein condensate is exposed to a sawtooth-like optical lattice potential, whose amplitude is periodically modulated in time. The ratchet transport arises from broken spatiotemporal symmetries of the driven potential, resulting in a desymmetrisation of transporting Eigenstates (Floquet states). The measured atomic current oscillates around a non-zero stationary value at longer observation times, shows resonances at positions determined by the photon recoil and depends on the initial phase of the drive, providing different lines of evidence for the full quantum character of the ratchet transport. The results provide a proof of principle demonstration of a quantum motor.

cond-mat.quant-gas↗

arXiv2009

Bloch oscillations of atoms in an optical multiphoton potential

We report on experiments studying transport properties of an atomic Bose-Einstein condensate in an optical lattice of spatial period $λ/2n$, where $n$ is an integer, realized with the dispersion of multiphoton Raman transitions. We observe Bloch oscillations, as a clear effect of quantum transport, in the sub-wavelength scale periodicity lattice. The unusually strong localisation of atoms is evident from the measured effective mass. Future prospects of the novel lattice structures are expected in the search for new quantum phases in tailored lattice structures up to quantum computing in optical nanopotentials.

cond-mat.other↗

arXiv2007

Dynamical Properties of a Rotating Bose-Einstein Condensate

Within a variational approach to solve the Gross-Pitaevskii equation we investigate dynamical properties of a rotating Bose-Einstein condensate which is confined in an anharmonic trap. In particular, we calculate the eigenfrequencies of low-energy excitations out of the equilibrium state and the aspect ratio of the condensate widths during the free expansion.

cond-mat.stat-mech↗

arXiv2007

Thermodynamical Properties of a Rotating Ideal Bose Gas

In a recent experiment, a Bose-Einstein condensate was trapped in an anharmonic potential which is well approximated by a harmonic and a quartic part. The condensate was set into such a fast rotation that the centrifugal force in the corotating frame overcompensates the harmonic part in the plane perpendicular to the rotation axis. Thus, the resulting trap potential became Mexican-hat shaped. We present an analysis for an ideal Bose gas which is confined in such an anharmonic rotating trap within a semiclassical approximation where we calculate the critical temperature, the condensate fraction, and the heat capacity. In particular, we examine in detail how these thermodynamical quantities depend on the rotation frequency.

cond-mat.stat-mech↗