How Law and Institutions Shape Financial Contracts: The Case of Bank Loans

We examine empirically how legal origin, creditor rights, property rights, legal formalism, and financial development affect the design of price and non-price terms of bank loans in almost 60 countries. Our results support the law and finance view that private contracts reflect differences in legal protection of creditors and the enforcement of contracts. Loans made to borrowers in countries where creditors can seize collateral in case of default are more likely to be secured, have longer maturity, and have lower interest rates. We also find evidence, however, that ?Coasian? bargaining can partially offset weak legal or institutional arrangements. For example, lenders mitigate risks associated with weak property rights and government corruption by securing loans with collateral and shortening maturity. Our results also suggest that the choice of loan ownership structure affects loan contract terms.

Fluctuation Theorems of Brownian Particles Controlled by a Maxwell's Demon

We study the stochastic dynamics of Brownian particles in a heat bath and subject to an active feedback control by an external, Maxwell's demon-like agent. The agent uses the information of the velocity of a particle and reduces its thermal agitation by applying a force. The entropy of the particle and the heat bath as a whole, thus, reduces. Entropy pumping [Phys. Rev. Lett. 93, 120602 (2004)] quantifies the entropy reduction. We discover that the entropy pumping has a dual role of work and heat contributing to free energy changes and entropy production of the open-system with the feedback control. Generalized Jarzynski equality and fluctuation theorems for work functional and entropy production are developed with the presence of the entropy pumping.Comment: 4 page

Valley Dependent Optoelectronics from Inversion Symmetry Breaking

Inversion symmetry breaking allows contrasted circular dichroism in different k-space regions, which takes the extreme form of optical selection rules for interband transitions at high symmetry points. In materials where band-edges occur at noncentral valleys, this enables valley dependent interplay of electrons with light of different circular polarizations, in analogy to spin dependent optical activities in semiconductors. This discovery is in perfect harmony with the previous finding of valley contrasted Bloch band features of orbital magnetic moment and Berry curvatures from inversion symmetry breaking [Phys. Rev. Lett. 99, 236809 (2007)]. A universal connection is revealed between the k-resolved optical oscillator strength of interband transitions, the orbital magnetic moment and the Berry curvatures, which also provides a principle for optical measurement of orbital magnetization and intrinsic anomalous Hall conductivity in ferromagnetic systems. The general physics is demonstrated in graphene where inversion symmetry breaking leads to valley contrasted optical selection rule for interband transitions. We discuss graphene based valley optoelectronics applications where light polarization information can be interconverted with electronic information.Comment: Expanded version, to appear in Phys. Rev.

Half metallic digital ferromagnetic heterostructure composed of a δ\delta-doped layer of Mn in Si

We propose and investigate the properties of a digital ferromagnetic heterostructure (DFH) consisting of a $\delta$-doped layer of Mn in Si, using \textit{ab initio} electronic-structure methods. We find that (i) ferromagnetic order of the Mn layer is energetically favorable relative to antiferromagnetic, and (ii) the heterostructure is a two-dimensional half metallic system. The metallic behavior is contributed by three majority-spin bands originating from hybridized Mn-$d$ and nearest-neighbor Si-$p$ states, and the corresponding carriers are responsible for the ferromagnetic order in the Mn layer. The minority-spin channel has a calculated semiconducting gap of 0.25 eV. Analysis of the total and partial densities of states, band structure, Fermi surfaces and associated charge density reveals the marked two-dimensional nature of the half metallicity. The band lineup is found to be favorable for retaining the half metal character to near the Curie temperature ($T_{C}$). Being Si based and possibly having a high $T_{C}$ as suggested by an experiment on dilutely doped Mn in Si, the heterostructure may be of special interest for integration into mature Si technologies for spintronic applications.Comment: 4 pages, 4 figures, Revised version, to appear in Phys. Rev. Let