Coherence assisted resonance with sub-lifetime-limited linewidth

We demonstrate a novel approach to obtain resonance linewidth below that limited by coherence lifetime. Cross correlation between induced intensity modulation of two lasers coupling the target resonance exhibits a narrow spectrum. 1/30 of the lifetime-limited width was achieved in a proof-of-principle experiment where two ground states are the target resonance levels. Attainable linewidth is only limited by laser shot noise in principle. Experimental results agree with an intuitive analytical model and numerical calculations qualitatively. This technique can be easily implemented and should be applicable to many atomic, molecular and solid state spin systems for spectroscopy, metrology and resonance based sensing and imaging.Comment: 5 pages 5 figure

Development of a time-to-digital converter ASIC for the upgrade of the ATLAS Monitored Drift Tube detector

The upgrade of the ATLAS muon spectrometer for high-luminosity LHC requires new trigger and readout electronics for the various elements of the detector. We present the design of a time-to-digital converter (TDC) ASIC prototype for the ATLAS Monitored Drift Tube (MDT) detector. The chip was fabricated in a GlobalFoundries 130 nm CMOS technology. Studies indicate that its timing and power consumption characteristics meet the design specifications, with a timing bin variation of 40 ps for all 48 channels with a power consumption of about 6.5 mW per channel.Comment: 9 pages, 12 figure

Enhancing the Critical Current of a Superconducting Film in a Wide Range of Magnetic Fields with a Conformal Array of Nanoscale Holes

The maximum current (critical current) a type-II superconductor can transmit without energy loss is limited by the motion of the quantized magnetic flux penetrating into a superconductor. Introducing nanoscale holes into a superconducting film has been long pursued as a promising way to increase the critical current. So far the critical current enhancement was found to be mostly limited to low magnetic fields. Here we experimentally investigate the critical currents of superconducting films with a conformal array of nanoscale holes that have non-uniform density while preserving the local ordering. We find that the conformal array of nanoscle holes provides a more significant critical current enhancement at high magnetic fields. The better performance can be attributed to its arching effect that not only gives rise to the gradient in hole-density for pinning vortices with a wide range of densities but also prevent vortex channeling occurring in samples with a regular lattice of holes.Comment: 5 pages, 3 figure

Yak and Tibet sheep grazing ingestion restrain seed germination of two Saussurea species in Tibetan meadow

Grazing disturbance had been defined as an important mechanism that allows the maintenance of species diversities in plant communities. To help understand effect of grazing on seed germination characteristics, we conducted a laboratory germination experiment with two Saussurea species, which were dominant species in alpine meadow communities of the Qinghai-Tibetan Plateau, and yak and Tibet sheep rumen juices. Results showed that yak rumen juices completely restrained seed germination for two species. Tibet sheep rumen juices significantly decreased seed germination percentage, germination index and weighted germination index, prolonged first germination time and mean germination time for two species. Saussurea japonica showed a significantly higher germination percentage, germination index and weighted germination index, but a significantly shorter first germination time and mean germination time than Saussurea iodostegia. Our study suggests that yak and Tibet sheep grazing ingestion may affect species population dynamic by significantly restraining seed germination in alpine area of the Qinghai-Tibetan Plateau.Key words: Rumen juices, seed germination, Saussurea iodostegia, Saussurea japonica

The single t-quark productions via the flavor-changing processes in the topcolor-assisted technicolor model at the hadron colliders

In the framework of topcolor-assisted technicolor(TC2) model, there exist tree-level flavor-changing (FC) couplings which can result in the loop-level FC coupling $tcg$. Such $tcg$ coupling can contribute significant clues at the forthcoming Large Hadron Collider (LHC) experiments. In this paper, based on the TC2 model, we study some single t-quark production processes involving $tcg$ coupling at the Tevatron and LHC: $pp(p\bar{p})\to t\bar{q}(q=u,d,s),tg$. We calculate the cross sections of these processes. The results show that the cross sections at the Tevatron are too small to observe the signal, but at the LHC it can reach a few pb. With the high luminosity, the LHC has considerable capability to find the single t-quark signal produced via some FC processes involving coupling $tcg$. On the other hand, these processes can also provide some valuable information of the coupling $tcg$ with detailed study of the processes and furthermore provide the reliable evidence to test the TC2 model.Comment: 15 pages, 10 figure

Negative longitudinal magnetoresistance in GaAs quantum wells

Negative longitudinal magnetoresistances (NLMRs) have been recently observed in a variety of topological materials and often considered to be associated with Weyl fermions that have a defined chirality. Here we report NLMRs in non-Weyl GaAs quantum wells. In the absence of a magnetic field the quantum wells show a transition from semiconducting-like to metallic behaviour with decreasing temperature. We observed pronounced NLMRs up to 9 Tesla at temperatures above the transition and weak NLMRs in low magnetic fields at temperatures close to the transition and below 5 K. The observed NLMRs show various types of magnetic field behaviour resembling those reported in topological materials. We attribute them to microscopic disorder and use a phenomenological three-resistor model to account for their various features. Our results showcase a new contribution of microscopic disorder in the occurrence of novel phenomena. They may stimulate further work on tuning electronic properties via disorder/defect nano-engineering

Electrical Conductivity Adjustment for Interface Capacitive-Like Storage in Sodium-Ion Battery

Sodium‐ion battery (SIB) is significant for grid‐scale energy storage. However, a large radius of Na ions raises the difficulties of ion intercalation, hindering the electrochemical performance during fast charge/discharge. Conventional strategies to promote rate performance focus on the optimization of ion diffusion. Improving interface capacitive‐like storage by tuning the electrical conductivity of electrodes is also expected to combine the features of the high energy density of batteries and the high power density of capacitors. Inspired by this concept, an oxide‐metal sandwich 3D‐ordered macroporous architecture (3DOM) stands out as a superior anode candidate for high‐rate SIBs. Taking Ni‐TiO2 sandwich 3DOM as a proof‐of‐concept, anatase TiO2 delivers a reversible capacity of 233.3 mAh g−1 in half‐cells and 210.1 mAh g−1 in full‐cells after 100 cycles at 50 mA g−1. At the high charge/discharge rate of 5000 mA g−1, 104.4 mAh g−1 in half‐cells and 68 mAh g−1 in full‐cells can also be obtained with satisfying stability. In‐depth analysis of electrochemical kinetics evidence that the dominated interface capacitive‐like storage enables ultrafast uptaking and releasing of Na‐ions. This understanding between electrical conductivity and rate performance of SIBs is expected to guild future design to realize effective energy storage