Laser-like vibrational instability in rectifying molecular conductors

We study the damping of molecular vibrations due to electron-hole pair excitations in donor-acceptor(D-A) type molecular rectifiers. At finite voltage additional non-equilibrium electron-hole pair excitations involving both electrodes become possible, and contribute to the stimulated emission and absorption of phonons. We point out a generic mechanism for D-A molecules, where the stimulated emission can dominate beyond a certain voltage due to inverted position of the D and A quantum resonances. This leads to current-driven amplification (negative damping) of the phonons similar to laser-action. We investigate the effect in realistic molecular rectifier structures using first principles calculations.Comment: 4 pages, 4 figure

Light emission and finite frequency shot noise in molecular junctions: from tunneling to contact

Scanning tunneling microscope induced light emission from an atomic or molecular junction has been probed from the tunneling to contact regime in recent experiments. There, the intensity of the light emission shows strong correlation with the current/charge fluctuations at optical frequencies. We show that this is consistent with the established theory in the tunneling regime, by writing the finite-frequency shot noise as a sum of inelastic transitions between different electronic states. Based on this, we develop a practical scheme to perform calculations on realistic structures using Green's functions. The photon emission yields obtained re-produce the essential feature of the experiments.Comment: published version, Phys. Rev. B 88, 045413 (2013

The Study of Chinese Nian Customs:Spring Festival Couplets

This paper focuses on the study of the unique art form of Chinese literature – Spring Festival couplets. It probes into the origin, evolution and history of the development of this typical Chinese Nian custom. It reveals the implications of Chinese culture and the connotations of the folklore contained in Spring Festival couplets. It shows the national psychology of optimism, positive attitude of life and the pursuit of happiness of Chinese people. Based on the study of many historical and modern literatures, the author approaches the subject from different angles and gives her understanding and opinions of the couplets in this paper. Key words: Spring Festival couplets; Customs; History; Characteristics; ConnotationRésumé: Le présent document se concentre sur l'étude de la forme d'art unique de la littérature chinoise - les couplets de la Fête du Printemps. Il sonde dans l'origine, dans l'évolution et dans l'histoire du développement de cette coutume de Nian typiquement chinois. Il révèle les implications de la culture chinoise et les connotations du folklore figurant dans les couplets de la Fête du Printemps. Il montre la psychologie nationale de l'optimisme, l'attitude positive de la vie et la poursuite du bonheur du peuple chinois. Sur la base de l'étude de nombreuses littératures modernes et historiques, l'auteur aborde le sujet sous des angles différents et donne sa propre compréhension et ses opinions des couplets dans le présent document.Mots-Clés: couplets de la Fête du Printemps; coutumes; histoire; charactéristiques; connotatio

A Comparative Study of Sino-US Festival Culture

Festival culture is an important carrier of the emotion and spirit of a nation. The study of holiday culture is an indispensable part of the study of a national culture. Since both American culture and Chinese culture have the characteristics of diversity and pluralism, a comparative study of them is meaningful. This paper studies some of the major festivals in both China and the United States of America, compares the similarities and the differences in the festival practices and trys to reveal the national personality, cultural value orientation, and the national spirit of them for the purpose of a better understanding and harmonious developmeng of the two cultures. Keywords: festival culture; comparative study; Sino-USRésumé: La culture festival est un vecteur important de l'émotion et l'esprit d'une nation. L'étude de la culture de vacances est un élément indispensable de l'étude d'une culture nationale. Comme la culture américaine et la culture chinoises ont toutes les deux les caractéristiques de la diversité et du pluralisme, une étude comparative d'entre eux est significative. Cet article étudie plusieurs grands festivaux en Chine et aux États-Unis, compare les similitudes et les différences dans les pratiques de festival et essaie de révéler la personnalité nationale, l'orientation des valeurs culturelles et l'esprit national pour une meilleure compréhension et un developpement harmonieux de ces deux cultures.Mots-clés: culture festival; étude comparative; sino-américai