39 research outputs found
Quantum oscillations of the critical current and high-field superconducting proximity in ballistic graphene
Graphene-based Josephson junctions provide a novel platform for studying the
proximity effect due to graphene's unique electronic spectrum and the
possibility to tune junction properties by gate voltage. Here we describe
graphene junctions with a mean free path of several micrometres, low contact
resistance and large supercurrents. Such devices exhibit pronounced
Fabry-P\'erot oscillations not only in the normal-state resistance but also in
the critical current. The proximity effect is mostly suppressed in magnetic
fields below 10mT, showing the conventional Fraunhofer pattern. Unexpectedly,
some proximity survives even in fields higher than 1 T. Superconducting states
randomly appear and disappear as a function of field and carrier concentration,
and each of them exhibits a supercurrent carrying capacity close to the
universal quantum limit. We attribute the high-field Josephson effect to
mesoscopic Andreev states that persist near graphene edges. Our work reveals
new proximity regimes that can be controlled by quantum confinement and
cyclotron motion
Quantum coherent control of a hybrid superconducting circuit made with graphene-based van der Waals heterostructures
Quantum coherence and control is foundational to the science and engineering
of quantum systems. In van der Waals (vdW) materials, the collective coherent
behavior of carriers has been probed successfully by transport measurements.
However, temporal coherence and control, as exemplified by manipulating a
single quantum degree of freedom, remains to be verified. Here we demonstrate
such coherence and control of a superconducting circuit incorporating
graphene-based Josephson junctions. Furthermore, we show that this device can
be operated as a voltage-tunable transmon qubit, whose spectrum reflects the
electronic properties of massless Dirac fermions traveling ballistically. In
addition to the potential for advancing extensible quantum computing
technology, our results represent a new approach to studying vdW materials
using microwave photons in coherent quantum circuits
Sexual dimorphism in cancer.
The incidence of many types of cancer arising in organs with non-reproductive functions is significantly higher in male populations than in female populations, with associated differences in survival. Occupational and/or behavioural factors are well-known underlying determinants. However, cellular and molecular differences between the two sexes are also likely to be important. In this Opinion article, we focus on the complex interplay that sex hormones and sex chromosomes can have in intrinsic control of cancer-initiating cell populations, the tumour microenvironment and systemic determinants of cancer development, such as the immune system and metabolism. A better appreciation of these differences between the two sexes could be of substantial value for cancer prevention as well as treatment