What is theoretical condensed matter physics, and why is it interesting?

Condensed Matter Physics is the study of the structure and behaviour of the matter that makes up most of the usual (and unusual) stuff that surrounds us every day. It is not the study of the very small (particle theory) or of the very large (astrophysics and cosmology) but of the things in between. It takes for granted that most of these are made up of electrons and nuclei interacting according to the well-established laws of electromagnetism and quantum mechanics, and tries to explain their properties.

What makes it an interesting and fundamental branch of physics? It turns out that large assemblies of electrons and nuclei in a condensed state often exhibit so-called cooperative behaviour which is quite different from that of the individual parts. Superconductivity, for example. And the study of this new behaviour requires theoretical methods which can be every bit as sophisticated as those of particle theory or relativity. In fact, mathematically they often have a lot in common. But while there is (we hope) only one `theory of everything' which describes the building blocks of matter, at intermediate scales there are any number of `effective' theories which account for the wealth of phenomena which we observe. Thus the subject is very diverse.

In condensed matter physics, experiment and observation play a key role. As compared with particle physics, most experiments are much easier to carry out, generally much more precise, and take far less time. So the link between experiment and theory is that much stronger.

Condensed matter physics is both fast-moving and outward looking. Developments come from fresh theoretical ideas, from ideas transplanted to a novel context, and from (sometimes serendipitous) experimental discoveries. Some of these developments involve topics at the interface between condensed matter physics and other fields - examples include atomic physics and biology.

Condensed matter physics is also very important because it often uncovers phenomena which are technologically important. As well as solid state devices, the whole field of polymers, complex fluids and other so-called `soft' condensed matter systems has all sorts of applications. More recently, the methods which condensed matter theorists use to study interacting systems with many degrees of freedom have been used to attack problems in such diverse fields as economics and the life sciences.

As a study in itself, as well as being a sound basis for any career where quantitative skills and problem-solving are at a premium, an apprenticeship in condensed matter theory is fascinating and invaluable.

Nombre: Franklin J. Quintero C.

Asignatura: CRF
Dirección: http://www-thphys.physics.ox.ac.uk/research/condensedmatter/intro.php
Ver Blog: http://franklinqcrf.blogspot.com/

The Inelastic Neutron Scattering Spectrum Of Nicotinic Acid And Its Assignment By Solid-State Density Functional Theory

Accepted in Chemical Physics Letters. What began as a reasonably straightforward inelastic neutron scattering (INS) assignment was expanded upon reviewer request to include an analysis of the potential for in-cell nicotinic acid (or niacin, depending on who you ask. Not to be confused with this Niacin, which would be another post altogether) prototropic tautomerization (technically, one might consider this just proton migration along the chain of the nicotinic acid molecules in the solid-state, which might just be more supported as, providing the punch line early, proton migration does not seem to occur in this system), a point that was mentioned in the paper as a possibility within the crystal cell but not originally examined as part of the spectral assignment. In the crystal cell picture shown below, tautomerization would result in proton H5 migrating to N’, yielding a chain (if it propagated down the entire one-dimensional chain of nicotinic acid molecules in the solid-state) of zwitterions (molecules with both positive and negative charges on the covalent framework). Anyone with experience in the solid-state study of amino acids knows that zwitterions are not only stable species in the solid-state, but they can also the dominant species in the solid-state, as ionic interactions and the dipole alignment that results from the alignment of, in this case, zwitterions, can yield greater stability than the neutral species, where only hydrogen bonding and dispersions forces occur in the crystal packing arrangement.

The inelastic neutron scattering assignment by solid-state density functional theory (DFT) strongly supports that, at the 25 K temperature of the neutron experiment, the crystal cell is of the neutral, non-zwitterionic form (as shown below, which labels the possible arrangements of hydrogens in the Z=4 crystal cell). Furthermore, despite the existence of several potentially stable proton arrangements in the crystal cell (the three additional forms shown below), the nicotinic acid crystal cell seems to prefer the neutral form even through room temperature. Fortunately, previous studies using other spectroscopic methods seem to agree. As has been the case for the vast majority of all of the previous INS studies, the solid-state DFT calculations were performed with DMol3 and the INS simulated spectra generated with Dr. A. J. Ramirez-Cuesta’s most excellent aClimax program.

As is often the case when a competent reviewer serves you a critical analysis of your submitted work, the final result is all the better for it.

Matthew R. Hudson, Damian G. Allis, and Bruce S. Hudson

Department of Chemistry, 1-014 Center for Science and Technology, Syracuse University, Syracuse, NY 13244-4100, USA

Keywords: nicotinic acid, niacin, vitamin B3, inelastic neutron scattering spectroscopy, solid-state density functional theory

Abstract: The 25 K inelastic neutron scattering (INS) spectrum of nicotinic acid has been measured and assigned by solid-state density functional theory (DFT). Vibrational mode energies involving the carboxylic acid proton are found to be significantly altered due to intermolecular hydrogen-bonding. There is good overall agreement between experiment and simulation in all regions of the spectrum, with identified deviations considered in detail by spectral region: phonon (25 – 300 cm-1), molecular (300 – 1600 cm-1), and high-frequency (>2000 cm-1). The relative energies, geometries, and vibrational spectra associated with hypothesized tautomerization in the solid-state have also been investigated.

Nombre: Franklin J. Quintero C.

Asignatura: CRF
Dirección: http://www.somewhereville.com/?p=563
Ver Blog: http://franklinqcrf.blogspot.com/

Experimental Polymer Physics

The polymer physics group conducts research on thermal and electrical properties of macromolecules in relation to structure. Macromolecules exhibit a wide variety of organizational structures, including disordered liquid phases, thermotropic liquid crystals, and true three-dimensional crystals. The liquid-to-solid state phase transformations in liquid crystalline polymers and polymer melts is investigated using dielectric relaxation spectroscopy, and wide and small angle X-ray scattering. Our research group travels to the Brookhaven National Laboratory several times a year to conduct scattering experiments using the high intensity X-radiation at the National Synchrotron Light Source.

In-house research facilities in the polymer physics group at Tufts include systems for measuring spatially resolved optical retardance, electric dipole relaxation, heat capacity and thermal properties. Wide angle X-ray diffraction and molecular modeling capabilties also exist in the polymer physics group. One fundamental problem we are studying is the kinetics of phase transformation in polymers, and the competition between ordering (eg., isotropic-to-nematic-to-crystal) and phase separation under the influence of external fields. In another project in the nano-technology area, we are investigating the effects of restricted dimensionality on the phase transformation kinetics in crystallizable thin films. The research in this group is interdisciplinary in nature, combining solid state physics with materials science.

The polymer physics group collaborates with researchers in the Biomedical Engineering Dept. at Tufts, and has shared facilities including the Biomaterials Characterization Laboratory. We are studying silk and silk-inspired diblock copolymers. Our model system consists of protein sequences found in native spider dragline silk and we use genetic variants of these sequences to provide the copolymer building blocks in order to assess relationships between block sequence and morphological and structural features. Target applications included drug delivery and medical implants based on silks which are biocompatible.

Recent students graduating with the Ph. D. from our group have been employed at Exxon Research Center, Michelin Americas Research Center, Assumption College, and Cisco Systems.

Nombre: Franklin J. Quintero C.

Asignatura: CRF
Dirección: https://wikis.uit.tufts.edu/confluence/display/cmp/Polymer+Physics
Ver Blog: http://franklinqcrf.blogspot.com/

Condensed Matter Physics

Condensed matter physics is the study of materials in the solid or liquid state, including their structure and mechanical, electrical, magnetic, thermal, optical and chemical properties. In addition to presenting rich and fascinating questions about the physical world, it is an area of physics with many real-world applications in such areas as microelectronics, information storage and communication, chemistry and the development and use of new materials. Students with strong backgrounds in condensed matter physics are often well qualified for research and engineering positions in industry, as well as for academic careers.

Experimental condensed matter physics at Tufts focuses on crystal structure and phase transitions in polymers and biopolymers, interactions of atoms and molecules with metal surfaces, ultrafast nonlinear optics and photonics, and the study of nanometer-scale biophysical systems. On-site facilities are housed in the modern Science and Technology Center, and include X-ray diffractometers, infrared spectrometers, ultrahigh vacuum surface analysis equipment, femtosecond lasers, scanning calorimeters, and atomic force microscopes. Researchers at Tufts also collaborate widely, including using facilities at Brookhaven National Laboratory.

Theoretical work at Tufts is concerned with the dynamic behavior of spin systems, including transitions caused both by thermally activated processes and by quantum tunneling.

Nombre: Franklin J. Quintero C.
Asignatura: CRF
Dirección: https://wikis.uit.tufts.edu/confluence/display/cmp/Home
Ver Blog: http://franklinqcrf.blogspot.com/

Liquid Crystals

The focus of our research activities is the physical chemistry of the liquid-crystalline state of matter. Classical topics of physical chemistry like the relation between structure and properties, thermodynamics and kinetics of phase transitions, electrical and optical properties of matter as well as structure and dynamics of low-dimensional and biological systems can be studied by means of liquid-crystalline systems in an excellent way. The following sections should deliver introductory insight into the research field of liquid crystals and its technical application.

Liquid crystals are liquids with long-range orientational order (anisotropic fluids), which combine the fluidity of ordinary liquids with the interesting electrical and optical properties of crystalline solids. They are observed as thermodynamically stable phases between the crystalline solid and ordinary isotropic liquid states (thermotropic liquid crystals). Liquid-crystalline structures result from self-organization of strongly anisometric molecules (Figure 1): The majority of liquid crystals are formed by rod-like (calamitic) molecules with a length of approximately 20 to 40 Ångströms. However disc-like (discotic) molecules, such as Phthalocyanincomplexes, Phospholipids as well as rigid DNA-double-helices also form liquid-crystalline systems.

Figure 1: Example of the self-organization of anisometric molecules in liquid-crystalline phases. On the left: rod-like molecules form a nematic liquid, in which the longitudinal axes of the molecules are parallelly aligned to a common preferred direction ("director"). On the right: disc-like (discotic) molecules arrange to molecule-stacks (columns), in which the longitudinal axes are also aligned parallely to the director. As a result of their orientational order, liquid crystals exhibit anisotropic physical properties, just like crystals.

Figure 2: Polarizing microscope picture of the formation of a nematic liquid crystal upon cooling out of the isotropic melt. Because of its optical anisotropy (birefringence) the liquid crystal appears bright between the crossed polarizers of the microscope. In the black areas (left side) we still have an optical isotropic melt.

A fascinating and characteristic feature of liquid-crystalline systems is, that they change their molecular and supermolecular organization drastically as an effect of very small external perturbations: The molecules in liquid crystal displays for instance are reoriented by relatively weak electrical fields. If one dissolves a small amount of chiral molecules in an achiral liquid-crystalline host phase, this results in remarkable macroscopic chirality effects, ranging from helical superstructures to the appearence of ferroelectricity. For this and other reasons liquid crystals - combined with polymers and colloids - are therefore summed up under the generic term ''Soft Matter" and treated under the branch of physical chemistry of condensed matter.

Figure 3: In liquid-crystalline systems elastic deformations are already induced by relatively weak perturbations (e.g. an electric field E). The scale of length of those deformations lies within the range of optical wave lenghts.

Figure 4: Schematic classification of the branch of "liquid crystals" into the physical chemistry of condensed matter.

Nombre: Franklin J. Quintero C.
Asignatura: CRF
Dirección:http://www.ipc.unistuttgart.de/~giesselm/AG_Giesselmann/Forschung/Fluessigkristalle/Fluessigkristalle.html
Ver Blog: http://franklinqcrf.blogspot.com/

State of matter

States of matter are the distinct forms that different phases of matter take on. Historically, the distinction is made based on qualitative differences in bulk properties. Solid is the state in which matter maintains a fixed volume and shape; liquid is the state in which matter maintains a fixed volume but adapts to the shape of its container; and gas is the state in which matter expands to occupy whatever volume is available.

More recently, distinctions between states have been based on differences in molecular interrelationships. Solid is the state in which intermolecular attractions keep the molecules in fixed spatial relationships. Liquid is the state in which intermolecular attractions keep molecules in proximity, but do not keep the molecules in fixed relationships. Gas is that state in which the molecules are comparatively separated and intermolecular attractions have relatively little effect on their respective motions. Plasma is a highly ionized gas that occurs at high temperatures. The intermolecular forces created by ionic attractions and repulsions give these compositions distinct properties, for which reason plasma is described as a fourth state of matter.

Forms of matter that are not composed of molecules and are organized by different forces can also be considered different states of matter. Fermionic condensate and the quark–gluon plasma are examples.

Although solid, gas and liquid are the most common states of matter on Earth, much of the baryonic matter of universe is in the form of hot plasma, both as rarefied interstellar medium and as dense stars.

States of matter may also be defined in terms of phase transitions. A phase transition indicates a change in structure and can be recognized by an abrupt change in properties. By this definition, a distinct state of matter is any set of states distinguished from any other set of states by a phase transition. Water can be said to have several distinct solid states. The appearance of superconductivity is associated with a phase transition, so there are superconductive states. Likewise, liquid crystal states and ferromagnetic states are demarcated by phase transitions and have distinctive properties.

This diagram shows the nomenclature for the different phase transitions.

Nombre: Franklin J. Quintero C.
Asignatura: CRF
Dirección: http://www.answers.com/topic/state-of-matter-1
Ver Blog: http://franklinqcrf.blogspot.com/

Condensed matter physics

Condensed matter physics is the field of physics that deals with the macroscopic and microscopic physical properties of matter. In particular, it is concerned with the "condensed" phases that appear whenever the number of constituents in a system is extremely large and the interactions between the constituents are strong. The most familiar examples of condensed phases are solids and liquids, which arise from the electromagnetic forces between atoms. More exotic condensed phases include the superconducting phase exhibited by certain materials at low temperature, the ferromagnetic and antiferromagnetic phases of spins on atomic lattices, and the Bose-Einstein condensate found in certain ultracold atomic systems.

The aim of condensed matter physics is to understand the behavior of these phases by using well-established physical laws, in particular those of quantum mechanics, electromagnetism and statistical mechanics. The diversity of systems and phenomena available for study makes condensed matter physics by far the largest field of contemporary physics. By one estimate,[citation needed] one third of all United States physicists identify themselves as condensed matter physicists. The field has a large overlap with chemistry, materials science, and nanotechnology, and there are close connections with the related fields of atomic physics and biophysics. Theoretical condensed matter physics also shares many important concepts and techniques with theoretical particle and nuclear physics.

Historically, condensed matter physics grew out of solid-state physics, which is now considered one of its main subfields. The name of the field was apparently[citation needed] coined in 1967 by Philip Anderson and Volker Heine when they renamed their research group in the Cavendish Laboratory of the University of Cambridge from "Solid-State Theory" to "Theory of Condensed Matter". In 1978, the Division of Solid State Physics at the American Physical Society was renamed as the Division of Condensed Matter Physics.[1] One of the reasons for this change is that many of the concepts and techniques developed for studying solids can also be applied to fluid systems. For instance, the conduction electrons in an electrical conductor form a Fermi liquid, with similar properties to conventional liquids made up of atoms or molecules. Even the phenomenon of superconductivity, in which the quantum-mechanical properties of the electrons lead to collective behavior fundamentally different from that of a classical fluid, is closely related to the superfluid phase of liquid helium.

Condensed matter physics

Nombre: Franklin J. Quintero C.

Asignatura: CRF

Dirección: http://www.answers.com/topic/condensed-matter-physics

Ver Blog: http://franklinqcrf.blogspot.com/