19 research outputs found
Violation of the London Law and Onsager-Feynman quantization in multicomponent superconductors
Non-classical response to rotation is a hallmark of quantum ordered states
such as superconductors and superfluids. The rotational responses of all
currently known single-component "super" states of matter (superconductors,
superfluids and supersolids) are largely described by two fundamental
principles and fall into two categories according to whether the systems are
composed of charged or neutral particles: the London law relating the angular
velocity to a subsequently established magnetic field and the Onsager-Feynman
quantization of superfluid velocity. These laws are theoretically shown to be
violated in a two-component superconductor such as the projected liquid
metallic states of hydrogen and deuterium at high pressures. The rotational
responses of liquid metallic hydrogen or deuterium identify them as a new class
of dissipationless states; they also directly point to a particular
experimental route for verification of their existence.Comment: Nature Physics in print. This is an early version of the paper. The
final version will be posted 6 months after its publication Nature Physics,
according to the journal polic
Quantized vortices in superfluid helium and atomic Bose-Einstein condensates
This article reviews recent developments in the physics of quantized vortices
in superfluid helium and atomic Bose-Einstein condensates. Quantized vortices
appear in low-temperature quantum condensed systems as the direct product of
Bose-Einstein condensation. Quantized vortices were first discovered in
superfluid 4He in the 1950s, and have since been studied with a primary focus
on the quantum hydrodynamics of this system. Since the discovery of superfluid
3He in 1972, quantized vortices characteristic of the anisotropic superfluid
have been studied theoretically and observed experimentally using rotating
cryostats. The realization of atomic Bose-Einstein condensation in 1995 has
opened new possibilities, because it became possible to control and directly
visualize condensates and quantized vortices. Historically, many ideas
developed in superfluid 4He and 3He have been imported to the field of cold
atoms and utilized effectively. Here, we review and summarize our current
understanding of quantized vortices, bridging superfluid helium and atomic
Bose-Einstein condensates. This review article begins with a basic
introduction, which is followed by discussion of modern topics such as quantum
turbulence and vortices in unusual cold atom condensates.Comment: 99 pages, 20 figures, Review articl
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Exotic vortices in superfluids and matrix product states for quantum optimization and machine learning
The interest in vortices and vortex lattices was sparked by the prediction of quantisation of circulation by Onsager in the 1940s. The field has since developed dramatically and attracted a lot of interest across the physics community. In this dissertation we study vortices in two different systems: a rotating, Rabi-coupled, two-component Bose--Einstein condensate (BEC) and a rotating spinor-BEC, in two spatial dimensions.
Vortex molecules can form in a two-component superfluid when a Rabi field drives transitions between the
two components. We study the ground state of an infinite system of vortex molecules in two dimensions, using
a numerical scheme which makes no use of the lowest Landau level approximation.
We find the ground state lattice geometry for different values of intercomponent interactions and strength of the Rabi field. In the limit of large field, when molecules are tightly bound, we develop a complementary analytical description. The energy
governing the alignment of molecules on a triangular lattice is found to correspond to that of an infinite system of
two-dimensional quadrupoles, which may be written in terms of an elliptic function . This allows for a numerical evaluation of the energy enabling us to find the ground state configuration of the molecules.
In the phase of a two-component BEC, in which the spin density is zero, the emergent of the order parameter allows for the presence of half-quantum vortices (HQVs). We numerically search for this object in the variational ground state of a spinor-BEC and find it in certain region of the phase diagram. We provide analytical arguments that suggest that this object is energetically favorable in the ground state.
Matrix product state (MPS) based methods are currently regarded as one of the most powerful tools to study the low-energy physics of one-dimensional many-body quantum systems. In this work we find a connection between MPS in the left canonical form and the Stiefel manifold. This relation allows us to constrain the optimisation to this subspace of the otherwise larger MPS manifold. We find that our method suffers from two undesirable features. First, the need of a large unit cell to achieve machine precision. Second, because of the presence of the power method in the variational energy expression, it is possible for the convergence process to get stuck in regions of the Stiefel manifold where the modulus of the second largest eigenvalue of the transfer matrix is very close to one.
Since the foundation of the field of (AI) in 1956, at a workshop held in Dartmouth College (New Hampshire, US), the excitement and optimism towards it has oscillated throughout the years. The last AI boom started in 2012 and we live in a time where people from disciplines, both in industry and academia, are getting involved in machine learning. We contribute to the field with a generative model for raw audio. Our model is based on continuous matrix product states and it takes the form of a , describing the continuous time measurement of a quantum system. We test our model on three different synthetic datasets and we find its performance promising
Physics of Neutron Star Crusts
The physics of neutron star crusts is vast, involving many different research
fields, from nuclear and condensed matter physics to general relativity. This
review summarizes the progress, which has been achieved over the last few
years, in modeling neutron star crusts, both at the microscopic and macroscopic
levels. The confrontation of these theoretical models with observations is also
briefly discussed.Comment: 182 pages, published version available at
<http://www.livingreviews.org/lrr-2008-10
Field Theoretic Aspects of Condensed Matter Physics: An Overview
In this chapter I discuss the impact of concepts of Quantum Field Theory in
modern Condensed Physics. Although the interplay between these two areas is
certainly not new, the impact and mutual cross-fertilization has certainly
grown enormously with time, and Quantum Field Theory has become a central
conceptual tool in Condensed Matter Physics. In this chapter I cover how these
ideas and tools have influenced our understanding of phase transitions, both
classical and quantum, as well as topological phases of matter, and dualities.Comment: Revised version to appear as a chapter in the Encyclopedia of
Condensed Matter Physics 2e. 126 pages, including 380 reference
Reaction rates and transport in neutron stars
Understanding signals from neutron stars requires knowledge about the
transport inside the star. We review the transport properties and the
underlying reaction rates of dense hadronic and quark matter in the crust and
the core of neutron stars and point out open problems and future directions.Comment: 74 pages; commissioned for the book "Physics and Astrophysics of
Neutron Stars", NewCompStar COST Action MP1304; version 3: minor changes,
references updated, overview graphic added in the introduction, improvements
in Sec IV.A.
Superconductors at the Nanoscale
By covering theory, design, and fabrication of nanostructured superconducting materials, this monograph is an invaluable resource for research and development. Examples are energy saving solutions, healthcare, and communication technologies. Key ingredients are nanopatterned materials which help to improve the superconducting critical parameters and performance of superconducting devices, and lead to novel functionalities. Contents Tutorial on nanostructured superconductors Imaging vortices in superconductors: from the atomic scale to macroscopic distances Probing vortex dynamics on a single vortex level by scanning ac-susceptibility microscopy STM studies of vortex cores in strongly confined nanoscale superconductors Type-1.5 superconductivity Direct visualization of vortex patterns in superconductors with competing vortex-vortex interactions Vortex dynamics in nanofabricated chemical solution deposition high-temperature superconducting films Artificial pinning sites and their applications Vortices at microwave frequencies Physics and operation of superconducting single-photon devices Josephson and charging effect in mesoscopic superconducting devices NanoSQUIDs: Basics & recent advances intrinsic Josephson junction stacks as emitters of terahertz radiation| Interference phenomena in superconductor-ferromagnet hybrids Spin-orbit interactions, spin currents, and magnetization dynamics in superconductor/ferromagnet hybrids Superconductor/ferromagnet hybrid