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Introduction

 

The Laboratoire de Physique des Solides (LPS) is a joint research unit of the Université Paris-Sud and the CNRS: the UMR 8502. It mainly depends on the CNRS Institute of Physics, and on the 28th section of the National Council of Universities. It gathers about a hundred researchers, experimentalists and theorists, and welcomes many students and visitors (more than sixty). Our research activity is supported by about 60 engineers, technicians and administrators.

At the LPS, we cover a wider variety of topics than our name suggests — “Laboratory of Solid State Physics”. In fact, we seek to address the physics of the condensed matter in all its diversity. We organise our research along three main topics or “axes”, each one involving roughly the same number of researchers:

New and exotic electronic states arise from three main causes: electronic correlations, symmetry of the electronic wavefunction, or non-linear response to large excitations. Electronic correlations promote the competition between different equilibrium states, resulting in phenomena like superconductivity, spin liquids or metal-insulator transitions. Topological electronic states occur when the symmetry of the electronic wavefunction is of different nature across the Brillouin zone, as is the case of the two-dimensional electron gas found at the surface of some oxides. Finally, a non-linear response to a large excitation can lead to a new electronic state, such as resistive switching, where an otherwise insulating material conducts when excited with a high voltage. This axis includes both experimental research (NMR, µSR, photoemission spectroscopy,…) and theoretical studies (numerical techniques such as ab-initio, quantum Monte-Carlo or dynamical mean-field theory, and analytical models).

Spatial confinement below the relevant length scales — such as domain size, quantum coherence length, superconducting correlation length, spin characteristic length, … — gives rise to new structural and quantum effects and renders nano-objects fundamentally different from bulk materials. The axis 2 covers the physics of these nano-materials, from their structural to their electronic, magnetic and optical properties. We explore these properties both experimentally and theoretically in a large variety of systems, such as thin layers, nanowires, dots, graphene, nanotubes or topological insulators.

This research axis gathers activities spanning the classical fields of “soft matter” (liquid crystals, surfactants, colloids, polymers, hybrid materials, …) and biophysics (confined DNA, viruses, membranes, cells, living tissues…). Using experiments, theory, and numerical simulations, we study the self-assembly, self-organisation, and dynamics of these systems and we try to describe them with the same physical concepts. Our research activity lies at the interface with chemistry and biology and makes intensive use of very large instruments such as synchrotrons and neutron reactors.