Optical tuning of exciton and trion emissions in monolayer phosphorene

Monolayer phosphorene provides a unique two-dimensional (2D) platform to investigate the fundamental dynamics of excitons and trions (charged excitons) in reduced dimensions. However, owing to its high instability, unambiguous identification of monolayer phosphorene has been elusive. Consequently, many important fundamental properties, such as exciton dynamics, remain underexplored. We report a rapid, noninvasive, and highly accurate approach based on optical interferometry to determine the layer number of phosphorene, and confirm the results with reliable photoluminescence measurements. Furthermore, we successfully probed the dynamics of excitons and trions in monolayer phosphorene by controlling the photo-carrier injection in a relatively low excitation power range. Based on our measured optical gap and the previously measured electronic energy gap, we determined the exciton binding energy to be ~0.3 eV for the monolayer phosphorene on SiO2/Si substrate, which agrees well with theoretical predictions. A huge trion binding energy of ~100 meV was first observed in monolayer phosphorene, which is around five times higher than that in transition metal dichalcogenide (TMD) monolayer semiconductor, such as MoS2. The carrier lifetime of exciton emission in monolayer phosphorene was measured to be ~220 ps, which is comparable to those in other 2D TMD semiconductors. Our results open new avenues for exploring fundamental phenomena and novel optoelectronic applications using monolayer phosphorene

Functional Foveal Splitting: Evidence from Neuropsychological and Multimodal MRI Investigations in a Chinese Patient with a Splenium Lesion

It remains controversial and hotly debated whether foveal information is double-projected to both hemispheres or split at the midline between the two hemispheres. We investigated this issue in a unique patient with lesions in the splenium of the corpus callosum and the left medial occipitotemporal region, through a series of neuropsychological tests and multimodal MRI scans. Behavioral experiments showed that (1) the patient had difficulties in reading simple and compound Chinese characters when they were presented in the foveal but left to the fixation, (2) he failed to recognize the left component of compound characters when the compound characters were presented in the central foveal field, (3) his judgments of the gender of centrally presented chimeric faces were exclusively based on the left half-face and he was unaware that the faces were chimeric. Functional MRI data showed that Chinese characters, only when presented in the right foveal field but not in the left foveal field, activated a region in the left occipitotemporal sulcus in the mid-fusiform, which is recognized as visual word form area. Together with existing evidence in the literature, results of the current study suggest that the representation of foveal stimuli is functionally split at object processing levels

Transmission Enhancement through Sub-Wavelength Aperture Based on Regulable Water-Based Metamaterial

A realization form of the Mie resonance with adjustable characteristics based on a water-based metamaterial is proposed. A novel local electromagnetic field coupling mechanism based on a water-based metamaterial is established, which is used for transmission enhancement through the sub-wavelength aperture for the first time. The water-based metamaterial particle for transmission enhancement at a specific frequency is designed. By designing the microfluidic control system to control the water filling (i.e., height) of the metamaterial particle, the adjustable transmission enhancement characteristics are realized. The influence of bilateral symmetry and flexible deformation of the metamaterial particle on the transmission characteristics is analyzed. The influence of the design parameters on the enhanced transmission characteristics is discussed

Implicit reading in Chinese pure alexia

Science and Technology Project of Zhejiang Province [2007C33007]; Zhejiang Province Funds [Y2080132]; Key Project of Education Department of Zhejiang Province [Z200805185]A number of recent studies have shown that some patients with pure alexia display evidence of implicit access to lexical and semantic information about words that they cannot read explicitly. This phenomenon has not been investigated systematically in Chinese patients. We report here a case study of a Chinese patient who met the criteria for pure alexia and had lesions in the left occipitotemporal region and the splenium of the corpus callosum. His explicit and implicit reading was evaluated with various stimuli in a number of tasks. We found that despite his severe impairment in overt reading and the definition of any characters, his performance was well above chance in various implicit tasks. His accuracy with respect to lexical decisions was so high that his performance was almost normal. These findings provide unequivocal evidence for the existence of implicit reading in Chinese patients with pure alexia and further support the involvement of the right hemisphere. (C) 2010 Elsevier Inc. All rights reserved

Transmission Enhancement through Sub-Wavelength Aperture Based on Regulable Water-Based Metamaterial

A realization form of the Mie resonance with adjustable characteristics based on a water-based metamaterial is proposed. A novel local electromagnetic field coupling mechanism based on a water-based metamaterial is established, which is used for transmission enhancement through the sub-wavelength aperture for the first time. The water-based metamaterial particle for transmission enhancement at a specific frequency is designed. By designing the microfluidic control system to control the water filling (i.e., height) of the metamaterial particle, the adjustable transmission enhancement characteristics are realized. The influence of bilateral symmetry and flexible deformation of the metamaterial particle on the transmission characteristics is analyzed. The influence of the design parameters on the enhanced transmission characteristics is discussed

Examples of compound and simple characters used in Experiment 1 and Experiment 2.

<p>A. Example of the two types of left-right structured Chinese characters presented centrally to the foveal field (behavioral Experiment 1.). Note that the left and right components were presented completely within the left and right halves of the foveal field; the red dot between the left and right components is the fixation point. B. Divided visual field presentation of simple characters (behavioral Experiment 2). Note that the whole character was presented either within the left or right foveal field; the red dot is the fixation point. C. Divided visual field presentation of compound characters (behavioral Experiment 2). Note that the whole character was presented either within the left or right foveal field; the red dot is the fixation point.</p

An example of the chimeric faces and its possible representations in the patient's two hemispheres.

<p>A. According to SFT, the information of the left half of the chimeric face (left to the fixation, half of a female face, upper panel) is exclusively projected to the right hemisphere (RH) and that of the right half of the chimeric face (right to the fixation, half of a male face, upper panel) is exclusively projected to the left hemisphere (LH). Because face recognition is right hemispheric dominant, the patients with interrupted splenium of the corpus callosum would make a gender judgment by the left part of the chimeric face (in this case, the patient would judge the chimeric face as a whole female face, owing to “hallucinated completions” of faces. [ Levy, Trevarthen and Sperry, 1972; Trevarthen and Kinsbourne, 1972] ). B. According to BPT, the information of the left half as well as right half of the chimeric face (upper panel) are projected simultaneously to both RH and LH. The patient would see both parts of the chimeric face.</p