13 research outputs found
Charge density wave and Weyl Semimetal phase in YIrO
The subtle interplay of band topology and symmetry broken phase, induced by
electron correlations, has immense contemporary relevance and potentially
offers novel physical insights. Here, we demonstrate charge density wave (CDW)
in bulk YIrO for T < 10 K, and its transition to the Weyl semimetal
(WSM) phase at higher temperatures. The CDW phase is evidenced by a) current
induced nonlinear conductivity with negative differential resistance at low
temperature, b) low frequency Debye like dielectric relaxation at low
temperature with a large dielectric constant, and c) an anomaly in the
temperature dependence of the thermal expansion coefficient. The WSM phase at
higher temperature is confirmed by the DC and AC transport measurements which
show an inductive response at low frequencies. More interestingly, we show that
by reducing the crystallite size, the low temperature CDW phase can be
eliminated leading to the restoration of the WSM phase.Comment: 5 pages, 4 figures; minor correction
A gate-tunable graphene Josephson parametric amplifier
With a large portfolio of elemental quantum components, superconducting
quantum circuits have contributed to dramatic advances in microwave quantum
optics. Of these elements, quantum-limited parametric amplifiers have proven to
be essential for low noise readout of quantum systems whose energy range is
intrinsically low (tens of eV ). They are also used to generate non
classical states of light that can be a resource for quantum enhanced
detection. Superconducting parametric amplifiers, like quantum bits, typically
utilize a Josephson junction as a source of magnetically tunable and
dissipation-free nonlinearity. In recent years, efforts have been made to
introduce semiconductor weak links as electrically tunable nonlinear elements,
with demonstrations of microwave resonators and quantum bits using
semiconductor nanowires, a two dimensional electron gas, carbon nanotubes and
graphene. However, given the challenge of balancing nonlinearity, dissipation,
participation, and energy scale, parametric amplifiers have not yet been
implemented with a semiconductor weak link. Here we demonstrate a parametric
amplifier leveraging a graphene Josephson junction and show that its working
frequency is widely tunable with a gate voltage. We report gain exceeding 20 dB
and noise performance close to the standard quantum limit. Our results complete
the toolset for electrically tunable superconducting quantum circuits and offer
new opportunities for the development of quantum technologies such as quantum
computing, quantum sensing and fundamental science
The Mordell-Weil bases for the elliptic curve
summary:Let be an elliptic curve over of the form , where is an integer. In this paper we prove that the two points and on can be extended to a basis for under certain conditions described explicitly
An asymptotic expansion of a Lambert series associated to cusp forms
by Kalyan Chakraborty, Abhishek Juyal, Shiv Datt Kumar and Bibekananda Maj
A gate-tunable graphene Josephson parametric amplifier
With a large portfolio of elemental quantum components, superconducting quantum circuits have contributed to dramatic advances in microwave quantum optics. Of these elements, quantum-limited parametric amplifiers have proven to be essential for low noise readout of quantum systems whose energy range is intrinsically low (tens of eV ). They are also used to generate non classical states of light that can be a resource for quantum enhanced detection. Superconducting parametric amplifiers, like quantum bits, typically utilize a Josephson junction as a source of magnetically tunable and dissipation-free nonlinearity. In recent years, efforts have been made to introduce semiconductor weak links as electrically tunable nonlinear elements, with demonstrations of microwave resonators and quantum bits using semiconductor nanowires, a two dimensional electron gas, carbon nanotubes and graphene. However, given the challenge of balancing nonlinearity, dissipation, participation, and energy scale, parametric amplifiers have not yet been implemented with a semiconductor weak link. Here we demonstrate a parametric amplifier leveraging a graphene Josephson junction and show that its working frequency is widely tunable with a gate voltage. We report gain exceeding 20 dB and noise performance close to the standard quantum limit. Our results complete the toolset for electrically tunable superconducting quantum circuits and offer new opportunities for the development of quantum technologies such as quantum computing, quantum sensing and fundamental science