arXiv subjects

U. Merkt

Publications and source records attributed to U. Merkt.

3 recordsLinked to original sources

arXiv2004

Supercurrent-phase relationship of a Nb/InAs(2DES)/Nb Josephson junction in overlapping geometry

Superconductor/normal conductor/superconductor (SNS) Josephson junctions with highly transparent interfaces are predicted to show significant deviations from sinusoidal supercurrent-phase relationships (CPR) at low temperatures. We investigate experimentally the CPR of a ballistic Nb/InAs(2DES)/Nb junction in the temperature range from 1.3 K to 9 K using a modified Rifkin-Deaver method. The CPR is obtained from the inductance of the phase-biased junction. Transport measurements complement the investigation. At low temperatures, substantial deviations of the CPR from conventional tunnel-junction behavior have been observed. A theoretical model yielding good agreement to the data is presented.

cond-mat.supr-con↗

arXiv2003

Coherent current transport in wide ballistic Josephson junctions

We present an experimental and theoretical investigation of coherent current transport in wide ballistic superconductor-two dimensional electron gas-superconductor junctions. It is found experimentally that upon increasing the junction length, the subharmonic gap structure in the current-voltage characteristics is shifted to lower voltages, and the excess current at voltages much larger than the superconducting gap decreases. Applying a theory of coherent multiple Andreev reflection, we show that these observations can be explained in terms of transport through Andreev resonances.

cond-mat.mes-hall↗

arXiv2001

Superconductivity-induced changes of the phonon resonances in RBa_2Cu_3O_7 (R=rare earth)

We observe a characteristic energy $\hbarω_{c}\approx 2.1$ eV which separates regions of different behavior of the phonon intensities in the Raman spectra of the $R\rm Ba_2Cu_3O_7$ system. A superconductivity-induced drop of phonon intensities is found for the oxygen modes O(4) and O(2)-O(3) only for excitation energies below $\hbarω_c$. This intensity drop indicates an order parameter which affects energies in the vicinity of $\hbarω_c$.

cond-mat.supr-con↗