We have investigated the defects introduced by Ar ion bombardment on cleaved MoS2 surface by scanning tunneling microscopy (STM). The resultant defects have been observed at room temperature as dark regions typically 6–8 nm in diameter and their contrast is found to depend on the sample bias voltage (SB). The high-temperature STM observations at 600°C and 800°C show a reduction of the diameter to 2–4 nm. Based on these experimental results it is concluded that the S atom complex produced at the defect site is partially negatively ionized and a depletion region of conduction electrons is produced around it. The observed lateral extent of the depletion region is in good agreement with that calculated from the repulsive Coulomb potential due to the negatively charged complex. The calculated screening length, however, disagrees with the observed size of the dark region.

The gigantic decrease of resistance by an applied magnetic field, which is often referred to as colossal magnetoresistance (CMR) 1-9 , has been an attracting phenomenon in strongly correlated electron systems. The discovery of CMR in manganese oxide compounds has developed the science of strong coupling among charge, orbital, and spin degrees of freedom. CMR is also attracting scientists from the viewpoint of possible applications to sensors, memories, and so on. However, no application using CMR effect has been achieved so far, partly because the CMR materials which satisfy all of the required conditions for the application, namely, high operating temperature, low operating magnetic field, and sharp resistive change, have not been discovered. Here we report a resistance change of more than two-orders of magnitude at a magnetic field lower than 2 T near 300 K in an A-site ordered NdBaMn 2 O 6 crystal. When temperature and a magnetic field sweep from insulating (metallic) phase to metallic (insulating) phase, the insulating (metallic) conduction changes to the metallic (insulating) conduction within 1 K and 0.5 T, respectively. The CMR is ascribed to the melting of the charge ordering. The entropy change which is estimated from the B-T phase diagram is smaller than what is expected for the charge and orbital ordering.The suppression of the entropy change is attributable to the loss of the short range ferromagnetic fluctuation of Mn spin moments, which an important key of the high temperature and low magnetic field CMR effect. arXiv:1811.07596v1 [cond-mat.str-el]

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Porphyrin-based molecules inserted into the oxide layer of a metal–oxide–semiconductor structure served as Coulomb islands. A Coulomb staircase originating from the single-electron tunneling was observed in a current–voltage curve. We found that light irradiation induced a shift in the Coulomb staircase. This shift was reversible; the shifted Coulomb staircase returned to its original position when the light irradiation was turned off. We thus demonstrated optical switching of a tunneling current. This result indicates that the molecular Coulomb islands have the potential to provide a range of optical functionality in single-electron tunneling devices.

How does an individual choose to pursue tertiary education in Indonesia in an era of mass tertiary education? What factors affect this decision? In thisarticle, we analyze the determinants of access to tertiary education in Indonesia from the demand side using household survey data. We also examine theimpact of regional and family background factors on inequity of access to tertiary education. In order to analyze the demand side factors for tertiaryeducation, we use a multi-nominal logit model to examine what factors influence an individual’s decision to pursue a sarjana (bachelor’s) program,diploma program, or work after s/he graduates from high school. The data used is from the fourth Indonesia Family Life Survey (IFLS4) which wasconducted by the RAND Corporation and others between 2007 and 2008. Key findings of the analysis are as follows: (1) the education level of the head ofhousehold and family income per household member have significant positive effects on the choice of pursuing tertiary education; (2) in urban areas, theeducation level of household spouse and students’ test scores in high school are positively significant; (3) living in urban areas per se does not have acorrelation with entry into tertiary education; (4) access to bachelor’s programs for urban residents is most likely affected by the family backgroundfactors; (5) holding everything else constant, the tendency is for females to enroll in diploma programs, but not for bachelor’s programs.

It is shown that the four-particle amplitude of superstring theory at two loops obtained in [1, 2] is equivalent to the previously obtained results in [3]- [5]. Here the Z 2 symmetry in hyperelliptic Riemann surface plays an important role in the proof.

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