arXiv subjects

A. Helzel

Publications and source records attributed to A. Helzel.

4 recordsLinked to original sources

arXiv2012

Counting Statistics and Dephasing Transition in an Electronic Mach-Zehnder Interferometer

It was recently suggested that a novel type of phase transition may occur in the visibility of electronic Mach-Zehnder Interferometers. Here, we present experimental evidence for the existence of this transition. The transition is induced by strongly non-Gaussian noise that originates from the strong coupling of a quantum point contact to the interferometer. We provide a transparent physical picture of the effect, by exploiting a close analogy to the neutrino-oscillations of particle physics. In addition, our experiment constitutes a probe of the singularity of the elusive full counting statistics of a quantum point contact.

cond-mat.mes-hall↗

arXiv2009

Measurement of the Transmission Phase through a Quantum Dot Embedded in One Arm of an Electronic Mach-Zehnder Interferometer

We investigate an electronic Mach-Zehnder interferometer with high visibility in the quantum Hall regime. The superposition of the electrostatic potentials from a quantum point contact (QPC) and the residual disorder potential from doping impurities frequently results in the formation of inadvertent quantum dots (QD) in one arm of the interferometer. This gives rise to resonances in the QPC transmission characteristics. While crossing the QD resonance in energy, the interferometer gains a phase shift of $\pi$ in the interference pattern.

cond-mat.mes-hall↗

arXiv2008

Edge Channel Interference Controlled by Landau Level Filling

We study the visibility of Aharonov-Bohm interference in an electronic Mach-Zehnder interferometer (MZI) in the integer quantum Hall regime. The visibility is controlled by the filling factor $ν$ and is observed only between $ν\approx 2.0$ and 1.0, with an unexpected maximum near $ν=1.5$. Three energy scales extracted from the temperature and voltage dependences of the visibility change in a very similar way with the filling factor, indicating that the different aspects of the interference depend sensitively on the local structure of the compressible and incompressible strips forming the quantum Hall edge channels.

cond-mat.mtrl-sci↗

arXiv2006

Nonlocal vortex motion in mesoscopic amorphous Nb0.7Ge0.3 structures

We study nonlocal vortex transport in mesoscopic amorphous Nb0.7Ge0.3 samples. A dc current I is passed through a wire connected via a perpendicular channel, of a length L= 2-5 um, with a pair of voltage probes where a nonlocal response Vnl ~ I is measured. The maximum of Rnl=Vnl/I for a given temperature occurs at an L-independent magnetic field and is proportional to 1/L. The results are interpreted in terms of the dissipative vortex motion along the channel driven by a remote current, and can be understood in terms of a simple model.

cond-mat.supr-con↗