H2020Индивидуална стипендия2021–2023

PhononMoments · Phonon Magnetic Moments and Angular Momentum in Flexible Framework Materials

„Хоризонт 2020“ — Действия „Мария Склодовска-Кюри“

Период: 2021-07-01 → 2023-06-30
Финансиране от ЕС: 191 149 €
Участници: 1
Схема: MSCA-IF

Линиите свързват координатора с партньорите.

Накратко на български

Хиралните фонони са вибрации на атомите в кристали, които се движат по кръг и създават магнитни полета. Разбирането на тези процеси помага да се разбере как се променят магнетизмът и преносът на топлина в различните материали.

Този кратък обзор е генериран от изкуствен интелект

Кратко обяснение, генерирано от езиков модел по текста на CORDIS. Оригиналът е по-долу.

Резултати накратко

Phonon Magnetic Moments and Angular Momentum in Flexible Framework Materials

When heat is added to a crystal, its atoms vibrate, generating tiny quantum excitations known as “phonons”. Understanding the behavior and properties of these phonons is crucial for advancing materials science and technology. When a phonon causes atoms to move in circles (see attached image), the phonon has an associated handedness, or chirality. Essentially, this means that phonons wherein the atoms rotate counter-clockwise can have distinct properties from those wherein the atoms move clockwise. These “chiral phonons” have only been intensely studied recently, and much remains unknown about how they affect the bulk properties of crystals. One of the most fascinating aspects of chiral phonons is that they can generate magnetic fields. If the atoms are electrically charged, their circular motions act like a tiny electric induction coil, producing magnetism. Since the charges of atoms are generally small in comparison to their mass, it was thought that this effect would be almost undetectably small. However, recent experiments have indicated much larger phonon-generated magnetic fields than initially thought, although the reason for this is still not perfectly understood. Since chiral phonons are still a relatively unstudied phenomenon, our research into them is principally fundamental in nature. If the properties of chiral phonons, and how they affect, for example, the magnetism or heat transfer of a material, are better understood, this could lead to new applications which cannot currently be foreseen. Indeed, one of these applications was unexpectedly discovered during the project, as described below. The first major goal of this research project was to use computational and theoretical techniques to study the magnetism of chiral phonons in a variety of materials, in order to determine if careful selection of the crystal structure could enhance the magnetic fields generated by phonons. A second goal was to study phonon magnetism in chiral materials (materials which have an inherent handedness). In these materials, phonons with non-zero momentum can naturally have a handedness and magnetism, whereas most previous studies had focused on phonons with near-zero momentum since these can be created using light. A third goal was to use the resulting theoretical predictions to detect chiral phonons experimentally.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз

Цел на проекта

This project will study how the magnetic moments and orbital angular momenta of phonons are related to chemical structure, electronic structure, and to each other. Phonons, which are particle-like vibrational excitations in solids, are not normally considered to have an angular momentum (a mechanical spin) or a magnetic moment (an electromagnetic spin). However, it has recently been discovered that vibrations that cause atoms to move in circles can in fact have these properties, although their magnitudes are thought to be extremely small in conventional materials. We aim to study these exotic properties of phonons in flexible framework materials, which are materials which combine extreme stiffness in some directions with extreme compliance in others. This combination can give rise to very low energy vibrational modes, which results in very large motions of the atoms, and therefore we expect flexible frameworks to have much larger phonon magnetic moments and angular momenta than in conventional materials. Our goal is to discover materials with very large phono-magnetic effects, ideally sufficiently large that they can be measured using existing experimental techniques. Large phono-magnetic effects would also allow the magnetic moment of the phonon to interact with magnetism due to the spins of electrons, leading to a heretofore undescribed physical interaction which could be useful in the study of magnetic materials. We will use computational and theoretical methods to study both materials where the circular motions of atoms require external stimulus to occur, and also chiral materials where the atoms can naturally move in circles. In this latter case, the introduction of magnetic order in the material can break the symmetry between phonons of one handedness and the other, potentially leading to emergent bulk effects such as a thermally driven angular momentum of the crystal as a whole.

Оригинален текст от CORDIS (на английски).

Участници

EIDGENOESSISCHE TECHNISCHE HOCHSCHULE ZUERICH · ZuerichКоординаторШвейцария