No abstract

The Compact Muon Solenoid collaboration is designing a new high-granularity endcap calorimeter, HGCAL, to be installed later this decade. As part of this development work, a prototype system was built, with an electromagnetic section consisting of 14 double-sided structures, providing 28 sampling layers. Each sampling layer has an hexagonal module, where a multipad large-area silicon sensor is glued between an electronics circuit board and a metal baseplate. The sensor pads of approximately 1.1 cm2 are wire-bonded to the circuit board and are readout by custom integrated circuits. The prototype was extensively tested with beams at CERN's Super Proton Synchrotron in 2018. Based on the data collected with beams of positrons, with energies ranging from 20 to 300 GeV, measurements of the energy resolution and linearity, the position and angular resolutions, and the shower shapes are presented and compared to a detailed Geant4 simulation.

We have performed magnetotransport measurements on a multi-layer graphene flake. At the crossing magnetic field Bc, an approximately temperature-independent point in the measured longitudinal resistivity ρxx, which is ascribed to the direct insulator-quantum Hall (I-QH) transition, is observed. By analyzing the amplitudes of the magnetoresistivity oscillations, we are able to measure the quantum mobility μq of our device. It is found that at the direct I-QH transition, μqBc ≈ 0.37 which is considerably smaller than 1. In contrast, at Bc, ρxx is close to the Hall resistivity ρxy, i.e., the classical mobility μBc is ≈ 1. Therefore, our results suggest that different mobilities need to be introduced for the direct I-QH transition observed in multi-layered graphene. Combined with existing experimental results obtained in various material systems, our data obtained on graphene suggest that the direct I-QH transition is a universal effect in 2D.

A quantum dot (QD) sensing device, fabricated from nanoscaled carbon material has been studied using of a bilayer graphene field effect transistor in order to enable its application to the detection of microwave (GHz) and/or terahertz (THz) radiation. Recently, it has been found that there exist several common features in low temperature quantum transport, found in experimental results of conductance quantization in a semiconductor QDs and the magnetoresistance of a graphene QDs. The applicability of a graphene field effect transistor at the GHz/THz range is discussed in terms of the microwave transconductance characteristics up to 40 GHz.

Multi-layer graphene has many unique properties for realizing graphene-based nano-electronic device applications as well as for fundamental studies. This paper mainly focuses on the conductance fluctuations in multi-layer graphene. The low-temperature saturation of dephasing time in multi-layer graphene is one order magnitude shorter than that in single-layer graphene, and the onset temperature of the low-temperature saturation of dephasing time in multi-layer graphene was significantly lower than that in single-layer graphene, which is noteworthy in the low-temperature saturation of dephasing time. We speculate that the carrier transport is shielded by capping transport and bottom layer graphene due to the substrate impurities and air molecules scattering.