Detection of the Faraday Chiral Anisotropy.

The connection between chirality and electromagnetism has attracted much attention through the recent history of science, allowing the discovery of crucial nonreciprocal optical phenomena within the context of fundamental interactions between matter and light. A major phenomenon within this family is the so-called Faraday chiral anisotropy, the long-predicted but yet unobserved effect which arises due to the correlated coaction of both natural and magnetically induced optical activities at concurring wavelengths in chiral systems. Here, we report on the detection of the elusive anisotropic Faraday chiral phenomenon and demonstrate its enantioselectivity. The existence of this fundamental effect reveals the accomplishment of envisioned nonreciprocal electromagnetic metamaterials referred to as Faraday chiral media, systems where novel electromagnetic phenomena such as negative refraction of light at tunable wavelengths or even negative reflection can be realized. From a more comprehensive perspective, our findings have profound implications for the general understanding of parity-violating photon-particle interactions in magnetized media.

Electrostatics of metal-graphene interfaces: sharp p-n junctions for electron-optical applications.

Creation of sharp lateral p-n junctions in graphene devices, with transition widths w well below the Fermi wavelength λF of graphene's charge carriers, is vital to study and exploit these electronic systems for electron-optical applications. The achievement of such junctions is, however, not trivial due to the presence of a considerable out-of-plane electric field in lateral p-n junctions, resulting in large widths. Metal-graphene interfaces represent a novel, promising and easy to implement technique to engineer such sharp lateral p-n junctions in graphene field-effect devices, in clear contrast to the much wider (i.e. smooth) junctions achieved via conventional local gating. In this work, we present a systematic and robust investigation of the electrostatic problem of metal-induced lateral p-n junctions in gated graphene devices for electron-optics applications, systems where the width w of the created junctions is not only determined by the metal used but also depends on external factors such as device geometries, dielectric environment and different operational parameters such as carrier density and temperature. Our calculations demonstrate that sharp junctions (w ≪ λF) can be achieved via metal-graphene interfaces at room temperature in devices surrounded by dielectric media with low relative permittivity (<10). In addition, we show how specific details such as the separation distance between metal and graphene and the permittivity of the gap in-between plays a critical role when defining the p-n junction, not only defining its width w but also the energy shift of graphene underneath the metal. These results can be extended to any two-dimensional (2D) electronic system doped by the presence of metal clusters and thus are relevant for understanding interfaces between metals and other 2D materials.

A Graphene-Edge Ferroelectric Molecular Switch.

We show that polar molecules (water, ammonia, and nitrogen dioxide) adsorbed solely at the exposed edges of an encapsulated graphene sheet exhibit ferroelectricity, collectively orienting and switching reproducibly between two available states in response to an external electric field. This ferroelectric molecular switching introduces drastic modifications to the graphene bulk conductivity and produces a large and ambipolar charge bistability in micrometer-size graphene devices. This system comprises an experimental realization of envisioned memory capacitive ("memcapacitive") devices whose capacitance is a function of their charging history, here conceived via confined and correlated polar molecules at the one-dimensional edge of a two-dimensional crystal.

Strong light-matter interaction in systems described by a modified Dirac equation.

The bulk states of some materials, such as topological insulators, are described by a modified Dirac equation. Such systems may have trivial and non-trivial phases. In this article, we show that in the non-trivial phase a strong light-matter interaction exists in a two-dimensional system, which leads to an optical conductivity at least one order of magnitude larger than that of graphene.

Renewal processes and fluctuation analysis of molecular motor stepping.

We present a systematic method of analysis of experiments performed with single motor proteins. The use of such a method should allow a more detailed description of the motor's chemical cycle through the precise fitting of the experimental data. We model the dynamics of a processive or rotary molecular motor using a renewal process, in line with the work initiated by Svoboda, Mitra and Block. We apply a functional technique to compute different types of multiple-time correlation function of the renewal process, which have applications to bead-assay experiments performed both with processive molecular motors, such as myosin V and kinesin, and rotary motors, such as F1-ATPase.

Domain wall roughening in dipolar films in the presence of disorder.

We derive a low-energy Hamiltonian for the elastic energy of a Néel domain wall in a thin film with in-plane magnetization, where we consider the contribution of the long-range dipolar interaction beyond the quadratic approximation. We show that such a Hamiltonian is analogous to the Hamiltonian of a one-dimensional polaron in an external random potential. We use a replica variational method to compute the roughening exponent of the domain wall for the case of two-dimensional dipolar interactions.