Vortex Dynamics in Amorphous MoSi Superconducting Thin Films

Vortex dynamics in superconductors have received a great deal of attention from both fundamental and applied researchers over the past few decades. Because of its critical role in the energy relaxation process of type II superconductors, vortex dynamics have been deemed a key factor for the emerging superconducting devices, but the effect of irradiation on vortex dynamics remains unclear. With the support of electrical transport measurements under external magnetic fields and irradiation, photon effect on vortex dynamics in amorphous MoSi (a MoSi) superconducting thin films are investigated in this work. The magnetic field dependent critical vortex velocity v* derived from the Larkin Ovchinnikov model is not significantly affected by irradiation. However, vortex depinning is found to be enhanced by photon-induced reduction in potential barrier, which mitigates the adverse effect of film inhomogeneity on superconductivity in the a MoSi thin films. The thorough understanding of the vortex dynamics in a MoSi thin films under the effect of external stimuli is of paramount importance for both further fundamental research in this area and optimization of future superconducting devices

(Nicholas Jose's "trans-cultural writing" in Avenue of Eternal Peace)

Avenue of Eternal Peace is an early novel written by Australian novelist Nicholas Jose. Set completely in China, the novel presents a panoramic description of a foreign culture with which the author has been closely associated. In that sense, it is Jose’s first "trans-cultural" novel. Jose claims that the novel represents an attempt on his part as an Australian writer to translate China. Indeed, Avenue of Eternal Peace offers a fascinating translation of Chinese culture. To Jose, cultural translation is different from interlingual translation because it all happens intralingually: it integrates the author’s understanding of the source culture and expression of it in the same process. In so doing Jose shapes his knowledge of a foreign culture through his own language and directly presents it to members of his own culture. This essay first looks into the contents of the Chinese culture in Jose’s translation. Employing what Raymond Williams refers to as the "three levels of culture", namely, the lived culture, the recorded culture and the culture of selective tradition, it then examines Jose’s translation strategies and offers a discussion of the underlying reasons. It concludes that the way in which Jose translates China in his early "trans-cultural" novels betrays a lot of affinities with what Bill Ashcroft calls the "transnational" writing in some postcolonial discourse

Noncollinear parametric fluorescence by chirped quasi-phase matching for monocycle temporal entanglement

Quantum entanglement of two photons created by spontaneous parametric downconversion (SPDC) can be used to probe quantum optical phenomena during a single cycle of light. Harris [Opt. Express 98, 063602 (2007)] suggested using ultrabroad parametric fluorescence generated from a quasi-phase-matched (QPM) device whose poling period is chirped. In the Harris's original proposal, it is assumed that the photons are collinearly generated and then spatially separated by frequency filtering. Here, we alternatively propose using noncollinearly generated SPDC. In our numerical calculation, to achieve 1.2 cycle temporal correlation for a 532 nm pump laser, only 10%-chirped device is sufficient when noncollinear condition is applied, while a largely chirped (50%) device is required in collinear condition. We also experimentally demonstrate an octave-spanning (790-1610 nm) noncollinear parametric fluorescence from a 10% chirped MgSLT crystal using both a superconducting nanowire single-photon detector and photomultiplier tube as photon detectors. The observed SPDC bandwidth is 194 THz, which is the largest width achieved to date for a chirped QPM device. From this experimental result, our numerical analysis predicts that the bi-photon can be compressed to 1.2 cycles with appropriate phase compensation

The value of using heterogeneous detector groups for the development of time-of-flight (TOF) positron emission tomography (PET) systems

Objective. Much recent attention on positron emission tomography (PET) is the development of time-of-flight (TOF) systems with ever-improving coincidence time resolution (CTR). This is because, when all other factors remain the same, a better CTR leads to images of better statistics and effectively increases the sensitivity of the system. However, detector designs that aggressively improve the CTR often compromise the detection efficiency (DE) and offset the benefit gained. Under this circumstance, in developing a TOF PET system it may be beneficial to employ heterogeneous detector groups to balance the overall CTR and DE of the system. In this study, we examine the potential value of this system design strategy by considering two-dimensional systems that assume several representative ways of mixing two detector groups. Approach. The study is based on computer simulation and specifically considers medium time-resolution (MTR) detectors that have a 528 ps CTR and high time-resolution (HTR) detectors that have a 100 ps CTR and a DE that is 0.7 times that of the MTR detector. We examine contrast recovery, noise, and subjective quality of the resulting images under various ways of mixing the MTR and HTR detectors. Main results. With respect to the traditional configuration that adopts only the HTR detectors, symmetric heterogeneous configurations may offer comparable or better images while using considerably fewer HTRs. On the other hand, asymmetric heterogeneous configurations may allow the use of only a few HTRs for improving image quality locally. Significance. This study demonstrates the value of the proposed system-level design strategy of using heterogeneous detector groups for achieving high effective system sensitivity by factoring into the tradeoff between the CTR and DE of the detector

An on-chip photon-pair source with negligible two-photon absoprtion

While photon-pair sources using silicon waveguides have shown great promise, strong two-photon absorption (TPA) may limit their brightness. Recently, high-index contrast doped glass (HICDG) has attracted attention because of its CMOS compatibility and low propagation loss. It is also expected that TPA in HICDG is small, though it has not yet been directly measured by conventionally used CW pumping. In this paper, we report that the estimated genuine coincidence events by photon-pairs increase quadratically as the pump power increased and do not show any saturation behavior up to 100 mW CW pump power. (C) 2019 The Japan Society of Applied Physic

Electronic Modulation of Non‐van der Waals 2D Electrocatalysts for Efficient Energy Conversion

The exploration of efficient electrocatalysts for energy conversion is important for green energy development. Owing to their high surface areas and unusual electronic structure, 2D electrocatalysts have attracted increasing interest. Among them, non-van der Waals (non-vdW) 2D materials with numerous chemical bonds in all three dimensions and novel chemical and electronic properties beyond those of vdW 2D materials have been studied increasingly over the past decades. Herein, the progress of non-vdW 2D electrocatalysts is critically reviewed, with a special emphasis on electronic structure modulation. Strategies for heteroatom doping, vacancy engineering, pore creation, alloying, and heterostructure engineering are analyzed for tuning electronic structures and achieving intrinsically enhanced electrocatalytic performances. Lastly, a roadmap for the future development of non-vdW 2D electrocatalysts is provided from material, mechanism, and performance viewpoints.Ministry of Education (MOE)This work was financially supported by the AcRF Tier 1 grant (RG105/19) from the Ministry of Education in Singapore; the UESTC start-up funding (A1098531023601243); the National Natural Science Foundation of China (U1401248, K121402819); the postdoctoral start-up funding in Soochow University (3231703217)