4 research outputs found
Reemergence of missing Shapiro steps in the presence of in-plane magnetic field
In the presence of a 4-periodic contribution to the current phase
relation, for example in topological Josephson junctions, odd Shapiro steps are
expected to be missing. While missing odd Shapiro steps have been observed in
several material systems and interpreted in the context of topological
superconductivity, they have also been observed in topologically trivial
junctions. Here, we study the evolution of such trivial missing odd Shapiro
steps in Al-InAs junctions in the presence of an in-plane magnetic field
. We find that the odd steps reappear at a crossover
value, exhibiting an in-plane field angle anisotropy that depends on spin-orbit
coupling effects. We interpret this behavior by theoretically analyzing the
Andreev bound state spectrum and the transitions induced by the non-adiabatic
dynamics of the junction. Our results highlight the complex phenomenology of
missing Shapiro steps and the underlying current phase relations in planar
Josephson junctions designed to realize Majorana states
Superconducting resonators with voltage-controlled frequency and nonlinearity
Voltage-tunable superconductor-semiconductor devices offer a unique platform
to realize dynamic tunability in superconducting quantum circuits. By
galvanically connecting a gated InAs-Al Josephson junction to a coplanar
waveguide resonator, we demonstrate the use of a wide-range gate-tunable
superconducting element. We show that the resonant frequency is controlled via
a gate-tunable Josephson inductance and that the non-linearity of the
voltage-controlled InAs-Al junction is non-dissipative as is the case with
conventional Al-AlO junctions. As the gate voltage is decreased, the
inductive participation of the junction increases up to , resulting in
the resonant frequency being tuned by over 2 GHz. Utilizing the wide tunability
of the device, we demonstrate that two resonant modes can be adjusted such that
they strongly hybridize, exhibiting an avoided level crossing with a coupling
strength of 51 MHz. Implementing such voltage-tunable resonators is the first
step toward realizing wafer-scale continuous voltage control in superconducting
circuits for qubit-qubit coupling, quantum-limited amplifiers, and quantum
memory platforms
Superconducting diode effect sign change in epitaxial Al-InAs Josephson junctions
Abstract There has recently been a surge of interest in studying the superconducting diode effect (SDE) partly due to the possibility of uncovering the intrinsic properties of a material system. A change of sign of the SDE at finite magnetic field has previously been attributed to different mechanisms. Here, we observe the SDE in epitaxial Al-InAs Josephson junctions with strong Rashba spin-orbit coupling (SOC). We show that this effect strongly depends on the orientation of the in-plane magnetic field. In the presence of a strong magnetic field, we observe a change of sign in the SDE. Simulation and measurement of supercurrent suggest that depending on the superconducting widths, W S, this sign change may not necessarily be related to 0–π or topological transitions. We find that the strongest sign change in junctions with narrow W S is consistent with SOC-induced asymmetry of the critical current under magnetic-field inversion, while in wider W S, the sign reversal could be related to 0–π transitions and topological superconductivity