Non-equilibrium breakdown of quantum Hall state in graphene

In this report we experimentally probe the non-equilibrium breakdown of the quantum Hall state in monolayer graphene by injecting a high current density ($\sim$1A/m). The measured critical currents for dissipationless transport in the vicinity of integer filling factors show a dependence on filling factor. The breakdown can be understood in terms of inter Landau level (LL) scattering resulting from mixing of wavefunctions of different LLs. To further study the effect of transverse electric field, we measured the transverse resistance between the $\nu=2$ to $\nu=6$ plateau transition for different bias currents and observed an invariant point.Comment: to appear in PRB Rapi

Strong backaction on a mechanical resonator by a few photons

Cavity electromechanical systems, consisting of a mechanical resonator coupled to an electromagnetic mode, are extensively used for sensing of various forces and controlling the vibrations of a mechanical mode down to their quantum limit. In the microwave domain, such devices based on magnetic-flux coupling have emerged as a promising platform with the potential to reach a single-photon strong coupling regime. Here, we demonstrate a flux-coupled electromechanical device using a frequency tunable superconducting transmon qubit, and a microwave cavity. By tuning the qubit in resonance with the cavity, the hybridized state (dressed mode) of the qubit and the cavity mode is used to achieve a magnetic field-dependent electromechanical coupling. It is established by performing an electromagnetically-induced transparency (EIT)-like experiment. At the largest applied field, we estimate the single-photon coupling rate of 60 kHz. Further, in the presence of the pump signal, we observe backaction, showing both cooling and heating of the mechanical mode. With a stronger pump, the dressed mode shows the signature of "super-splitting", and a strong backaction on the mechanical resonator, reflected in the broadening of the mechanical linewidth by a factor of 42 while using less than 1 photon in the dressed mode.Comment: Total 9 figures; 13 page

Simulation Based Analysis of Temperature Effect on Breakdown Voltage of Ion Implanted Co/n-Si Schottky Diode

In semiconductor devices, breakdown voltage variation with temperature is a very significant study, since the reliability and performance of semiconductor devices especially depends upon the temperature. In this paper, the influence of temperature on breakdown characteristic of Ion Implanted edge terminated Co/n-Si Schottky Diode formed on n-Si epitaxial layer has been investigated by using SILVACO TCAD. It is also reported that not only resistive area present in close proximity to the edges of boron ion implanted Schottky diode are responsible for improvement in breakdown voltage but also the formation of PN junction near the edges, affect the breakdown voltage to a significant amount. The dopant concentration of epitaxial layer is 1 × 1015/cm3. The variation in reverse breakdown characteristics as a junction of temperature in the range of 300-1000 K is presented in this paper. A comparative study of breakdown voltages of Ion Implanted and as-prepared Schottky diode is also presented. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3026

Multi-mode ultra-strong coupling in circuit quantum electrodynamics

With the introduction of superconducting circuits into the field of quantum optics, many novel experimental demonstrations of the quantum physics of an artificial atom coupled to a single-mode light field have been realized. Engineering such quantum systems offers the opportunity to explore extreme regimes of light-matter interaction that are inaccessible with natural systems. For instance the coupling strength $g$ can be increased until it is comparable with the atomic or mode frequency $\omega_{a,m}$ and the atom can be coupled to multiple modes which has always challenged our understanding of light-matter interaction. Here, we experimentally realize the first Transmon qubit in the ultra-strong coupling regime, reaching coupling ratios of $g/\omega_{m}=0.19$ and we measure multi-mode interactions through a hybridization of the qubit up to the fifth mode of the resonator. This is enabled by a qubit with 88% of its capacitance formed by a vacuum-gap capacitance with the center conductor of a coplanar waveguide resonator. In addition to potential applications in quantum information technologies due to its small size and localization of electric fields in vacuum, this new architecture offers the potential to further explore the novel regime of multi-mode ultra-strong coupling.Comment: 15 pages, 9 figure

Approaching ultra-strong coupling in Transmon circuit-QED using a high-impedance resonator

In this experiment, we couple a superconducting Transmon qubit to a high-impedance $645\ \Omega$ microwave resonator. Doing so leads to a large qubit-resonator coupling rate $g$, measured through a large vacuum Rabi splitting of $2g\simeq 910$ MHz. The coupling is a significant fraction of the qubit and resonator oscillation frequencies $\omega$, placing our system close to the ultra-strong coupling regime ($\bar{g}=g/\omega=0.071$ on resonance). Combining this setup with a vacuum-gap Transmon architecture shows the potential of reaching deep into the ultra-strong coupling $\bar{g} \sim 0.45$ with Transmon qubits