Attosecond science, studies of electron dynamics in their natural time scale, stems from the development of mostly extreme ultraviolet sources through high-order harmonic generation in gas-phase systems. Recently, being ignited by the researches done in Stanford, high-order harmonic generation in solids has been discovered and been actively investigated. The coherent, extreme ultraviolet radiation from solids can be utilized not only as a new source for technical applications but it also offers a great tool to study electronic properties of solids. In this talk, we briefly review the developments in this emerging field and we report our newest results. In details, we demonstrate the first polarimetry measurement of high-order harmonic generation from solids and use it to uncover the non-vanishing Berry curvature underlying the generation of even harmonics in quartz, in orthogonal polarization with respect to the linearly incident electric field. First ab initio calculation of Berry curvature of quartz has been carried out and it shows a high degree of agreement to the experimentally retrieved Berry curvature which concludes an important spectroscopic application. Furthermore, we extend high-order harmonic generation in condensed matter by reporting on the unambiguous, systematic, experimental investigations of the high-order harmonic generation in liquids, the third phase of matter. By utilizing a liquid flat-jet as a target for light-matter interaction, coherent, intense extreme ultraviolet radiation is recorded in the form of multiple odd-order harmonics reaching up to 27 order and extending beyond 20 electron Volt. The intensity scaling and the ellipticity measurement show the non-perturbative, solid-like nature of the radiation. Highest cut-off energy photons were obtained using ethanol by comparison to water and other liquids. Our investigation serves as a promising first step in utilizing the new source of coherent extreme ultraviolet radiation as well as exploring electron dynamics in liquid-phase of matter.
The talk is devoted to recent advance in the field of low-dimensional electronic systems with induced superconductivity and nontrivial topological properties. The examples of such systems are topological insulators and semiconducting nanowires, carrying Majorana modes. The main focus of the talk is on the microscopic theory of the induced topological superconducting ordering and of the properties of underlying Majorana states. In particular, we investigate the consequences of the inverse proximity effect in these hybrid structures and discuss the resulting restrictions on the dynamical operation of Majorana-based devices. We concern as well the distinctive features of the superconducting order parameter and dynamics of quasiparticle modes leading to the beating dynamics of subgap quasiparticles and the effect of this dynamical phenomenon on the topological protection and quantum teleportation of Majorana states.
We show that a conformal anomaly in Weyl/Dirac semimetals generates a bulk electric current perpendicular to a temperature gradient and the direction of a background magnetic field. The associated conductivity of this novel contribution to the Nernst effect is fixed by a beta function associated with the electric charge renormalization in the material. I will give a pedagogical introduction to anomaly related response functions.
The input-output relations of a molecular machine summarize its biological functional characteristics. Therefore, answering many fundamental questions on molecular machines ultimately reduce to understanding their input-output relations. Many chemical reactions, particularly reactions catalyzed by enzymes, follow one of the few “universal” relations between input concentrations and output concentration of the molecular species involved in the reaction. We begin with a graph theoretic analysis of the input-output relation of a single enzyme. Input-output response of a graph can be characterized by the steady-state concentrations of the vertices. This analysis sets the stage for understanding, at the next level of complexity, the input-output relation of a molecular machine, that is a macromolecular complex, and then at an even broader context of a group of interacting machines. I'll present an overview of our recent results on these input-output relations at multiple scales.
Ensembles of atoms or other quantum emitters are envisioned to be an important component of quantum applications, ranging from quantum memories for light to photon-photon gates to metrology. It has historically been an outstanding challenge to exactly solve for the quantum dynamics of an optical field as it propagates through and interacts with an ensemble. The standard axiomatic approach is to use the one-dimensional Maxwell-Bloch equations, which treats the interaction between the ensemble and a quasi-1D optical mode of interest, while the interaction with the remaining 3D continuum of modes is assumed to result in independent spontaneous emission of excited atoms. Strictly speaking, this assumption cannot be correct, as the emission of light is a wave phenomenon, and thus the emitted intensity must depend on interference and correlations between the atoms. Here, we discuss an alternative theoretical approach, which accounts for interference and the precise atomic positions. In this formalism, an interacting quantum spin model describes the dynamics of the atomic internal degrees of freedom under multiple photon scattering, while the field properties can subsequently be re-constructed from the spin correlations. Using this model, we then show how interference can be exploited as an extremely powerful resource to suppress the unwanted emission of light and the subsequent loss of information into undesirable directions. The effects of interference are particularly prominent in ordered arrays of emitters. As two specific examples, we construct a new protocol for a quantum memory for light based upon an ordered array, whose error rate as a function of system resources scales exponentially better than previously known bounds. We also show the interrogation time in an optical lattice clock can be significantly extended, through the excitation of collective subradiant atomic states whose spontaneous emission rates are strongly suppressed. These results raise the intriguing question of whether interference can be used to broadly re-define the performance limits of all applications involving atomic light-matter interfaces.