218 research outputs found
Possible signatures of mixed-parity superconductivity in doped polar SrTiO3 films
Superconductors that possess both broken spatial inversion symmetry and
spin-orbit interactions exhibit a mix of spin singlet and triplet pairing.
Here, we report on measurements of the superconducting properties of
electron-doped, strained SrTiO3 films. These films have an enhanced
superconducting transition temperature and were previously shown to undergo a
transition to a polar phase prior to becoming superconducting. We show that
some films show signatures of an unusual superconducting state, such as an
in-plane critical field that is higher than both the paramagnetic and orbital
pair breaking limits. Moreover, nonreciprocal transport, which reflects the
ratio of odd versus even pairing interactions, is observed. Together, these
characteristics indicate that these films provide a tunable platform for
investigations of unconventional superconductivity
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
Quasiparticle dynamics in epitaxial Al-InAs planar Josephson junctions
Quasiparticle (QP) effects play a significant role in the coherence and
fidelity of superconducting quantum circuits. The Andreev bound states of high
transparency Josephson junctions can act as low-energy traps for QPs, providing
a mechanism for studying the dynamics and properties of both the QPs and the
junction. We study the trapping and clearing of QPs from the Andreev bound
states of epitaxial Al-InAs Josephson junctions incorporated in a
superconducting quantum interference device (SQUID) galvanically shorting a
superconducting resonator to ground. We use a neighboring voltage-biased
Josephson junction to inject QPs into the circuit. Upon the injection of QPs,
we show that we can trap and clear QPs when the SQUID is flux-biased. We
examine effects of the microwave loss associated with bulk QP transport in the
resonator, QP-related dissipation in the junction, and QP poisoning events. By
monitoring the QP trapping and clearing in time, we study the dynamics of these
processes and find a time-scale of few microseconds that is consistent with
electron-phonon relaxation in our system and correlated QP trapping and
clearing mechanisms. Our results highlight the QP trapping and clearing
dynamics as well as the associated time-scales in high transparency Josephson
junctions based fabricated on Al-InAs heterostructures
The Lantern Vol. 2, No. 1, December 1933
• Petition • Keep it Burning! • Jes\u27 Before Christmas • Noel: Translation from Theophile Gautier • A Young Jew Meets Jesus • Book Review: Little Man, What Now? • Book Review: Thunder and Dawn • Continuity • La Veille de Noel (Reflexions d\u27un Provincial) • Noel Sceptique par Jules LaFargue • Horizon • Winter Night • Linoleum Cutshttps://digitalcommons.ursinus.edu/lantern/1001/thumbnail.jp
Characterizing losses in InAs two-dimensional electron gas-based gatemon qubits
The tunnelling of cooper pairs across a Josephson junction (JJ) allow for the
nonlinear inductance necessary to construct superconducting qubits, amplifiers,
and various other quantum circuits. An alternative approach using hybrid
superconductor-semiconductor JJs can enable superconducting qubit architectures
with all electric control. Here we present continuous-wave and time-domain
characterization of gatemon qubits and coplanar waveguide resonators based on
an InAs two-dimensional electron gas. We show that the qubit undergoes a vacuum
Rabi splitting with a readout cavity and we drive coherent Rabi oscillations
between the qubit ground and first excited states. We measure qubit relaxation
times to be 100 ns over a 1.5 GHz tunable band. We detail the loss
mechanisms present in these materials through a systematic study of the quality
factors of coplanar waveguide resonators. While various loss mechanisms are
present in III-V gatemon circuits we detail future directions in enhancing the
relaxation times of qubit devices on this platform
Measurement of inclusive D*+- and associated dijet cross sections in photoproduction at HERA
Inclusive photoproduction of D*+- mesons has been measured for photon-proton
centre-of-mass energies in the range 130 < W < 280 GeV and a photon virtuality
Q^2 < 1 GeV^2. The data sample used corresponds to an integrated luminosity of
37 pb^-1. Total and differential cross sections as functions of the D*
transverse momentum and pseudorapidity are presented in restricted kinematical
regions and the data are compared with next-to-leading order (NLO) perturbative
QCD calculations using the "massive charm" and "massless charm" schemes. The
measured cross sections are generally above the NLO calculations, in particular
in the forward (proton) direction. The large data sample also allows the study
of dijet production associated with charm. A significant resolved as well as a
direct photon component contribute to the cross section. Leading order QCD
Monte Carlo calculations indicate that the resolved contribution arises from a
significant charm component in the photon. A massive charm NLO parton level
calculation yields lower cross sections compared to the measured results in a
kinematic region where the resolved photon contribution is significant.Comment: 32 pages including 6 figure
Measurement of Jet Shapes in Photoproduction at HERA
The shape of jets produced in quasi-real photon-proton collisions at
centre-of-mass energies in the range GeV has been measured using the
hadronic energy flow. The measurement was done with the ZEUS detector at HERA.
Jets are identified using a cone algorithm in the plane with a
cone radius of one unit. Measured jet shapes both in inclusive jet and dijet
production with transverse energies GeV are presented. The jet
shape broadens as the jet pseudorapidity () increases and narrows
as increases. In dijet photoproduction, the jet shapes have been
measured separately for samples dominated by resolved and by direct processes.
Leading-logarithm parton-shower Monte Carlo calculations of resolved and direct
processes describe well the measured jet shapes except for the inclusive
production of jets with high and low . The observed
broadening of the jet shape as increases is consistent with the
predicted increase in the fraction of final state gluon jets.Comment: 29 pages including 9 figure
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