Valley excitons in two-dimensional semiconductors

Monolayer group-VIB transition metal dichalcogenides have recently emerged as a new class of semiconductors in the two-dimensional limit. The attractive properties include: the visible range direct band gap ideal for exploring optoelectronic applications; the intriguing physics associated with spin and valley pseudospin of carriers which implies potentials for novel electronics based on these internal degrees of freedom; the exceptionally strong Coulomb interaction due to the two-dimensional geometry and the large effective masses. The physics of excitons, the bound states of electrons and holes, has been one of the most actively studied topics on these two-dimensional semiconductors, where the excitons exhibit remarkably new features due to the strong Coulomb binding, the valley degeneracy of the band edges, and the valley dependent optical selection rules for interband transitions. Here we give a brief overview of the experimental and theoretical findings on excitons in two-dimensional transition metal dichalcogenides, with focus on the novel properties associated with their valley degrees of freedom.Comment: Topical review, published online on National Science Review in Jan 201

Strategic Pricing in Service Industries.

This dissertation studies several strategic-level pricing decisions of firms that are motivated by recent changes of pricing policies in several service industries. It consists of three essays, each analyzing a different problem of selecting the optimal pricing policy for firms in a certain service industry. All three essays contribute to the arising areas of strategic-level revenue management and consumer-driven operations management. The first essay studies whether preventing resale of tickets benefits the ticket providers for sporting and entertainment events. Different from what common wis- dom may suggest, I find that this event organizers can benefit from reductions in consumers’ (and speculators’) transaction costs of resale in many cases. Further, I propose ticket options (where consumers would initially purchase an option to buy a ticket and then exercise at a later date) as a novel ticket pricing policy, and show that ticket options naturally reduce ticket resale and increase event organizers’ revenues. The second essay studies a conditional upgrade strategy that has recently become common in the travel industry. A consumer can accept a conditional upgrade offer after making a reservation and pay the fee to upgrade at check-in if the higher-quality product type is still available. I identify multiple benefits of conditional upgrades including demand expansion, price correction, and risk management. Moreover, I find that using conditional upgrades can generate higher revenues than having the ability to optimize product prices and use dynamic pricing. The third essay studies the firm’s strategic decision of whether to bundle the an- cillary service (e.g., baggage delivery) into the main service (e.g., air travel) or to unbundle and charge separate prices. I find that a firm that can price-discriminate when selling the main service should unbundle the ancillary service because con- sumers’ likelihoods of purchasing the ancillary service are low, or a large proportion of consumers are myopic instead of forward-looking, or the firm is dependent on inter- mediaries to make sales. I also find that the firm’s ability to price-discriminate when selling the main service reverses some classic bundling results for a uniform-pricing firm.PhDBusiness AdministrationUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/113531/1/cuiyao_1.pd

Fast and accurate simulations of transmission-line metamaterials using transmission-matrix method

Recently, two-dimensional (2D) periodically L and C loaded transmission-line (TL) networks have been applied to represent metamaterials. The commercial Agilent's Advanced Design System (ADS) is a commonly-used tool to simulate the TL metamaterials. However, it takes a lot of time to set up the TL network and perform numerical simulations using ADS, making the metamaterial analysis inefficient, especially for large-scale TL networks. In this paper, we propose transmission-matrix method (TMM) to simulate and analyze the TL-network metamaterials efficiently. Compared to the ADS commercial software, TMM provides nearly the same simulation results for the same networks. However, the model-process and simulation time has been greatly reduced. The proposed TMM can serve as an efficient tool to study the TL-network metamaterials.Comment: 15 pages, 13 figure