A new law gives the energy needed to fracture stretchable networks
https://phys.org/news/2025-03-law-energy-fracture-stretchable-networks.html
Phys.org · A new law gives the energy needed to fracture stretchable networks
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Fractional quantum Hall states in atom arrays
Our second approach to create a topological order in atom arrays is to focus on a different kind of topological order: fractional quantum Hall (FQH) states. These were first discovered in condensed matter. It is possible to confine electrons to move in two-dimensions only (such as in the 2D material graphene or in so-called metal-oxide-semiconductor transistors) and then put them in a strong perpendicular magnetic fields. The electrons then move in circles (so-called “cyclotron motion”), but since they are quantum objects, only some values of radius are allowed. Thus, the energy can only take certain fixed values (we call them “Landau levels”). There are however different possibilities of an electron having the same energy, because the center of the orbit can be located in different places – we say that Landau levels are “degenerate”. And when there is degeneracy, the interaction between electrons becomes very important. Without interactions, there are many possible ways of arranging electrons within a Landau level, all with the same energy. In the presence of interactions, some arrangements become preferred – and it turns out those correspond to topological orders known as the FQH states. Such systems host anyons which look like fractions of an electron – like somehow the electron split into several parts.
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Spin liquids in Rydberg atom arrays in cavities
What is our proposal for the realization of spin liquid?
We consider an atom array held by optical tweezers and placed in an optical cavity. The cavity consists of two mirrors placed on the opposite sides of the system. The photons which normally would escape the system (at least some of them) will bounce back and forth between the mirrors. In such a configuration, the distance between atoms becomes irrelevant and the probability of an excitation hopping between any two atoms becomes the same.
The second ingredient is that the excited state of the atoms would be a Rydberg state – a very high-energy state where the electron is far away from the nucleus. The atoms in Rydberg states interact strongly by van der Waals forces. In our case it would mean that two excitations will have much higher energy when they are at nearest-neighboring atoms than if they are far away.
This setting seems much different from usual crystals. In the typical material, the electrons are much more likely to hop between nearest-neighboring atoms than far-away ones, while in our case they would be able hop arbitrarily far with the same probability. But it turns out that there is in equivalence between such “infinite-range hopping + Rydberg” model and the Heisenberg model, commonly used to describe magnets, including the frustrated ones.
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#Physics #Quantum #TopologicalOrder #CondMat #CondensedMatter #QuantumOptics #Science
Atom arrays
Scientists have developed ways of trapping atoms and arranging them in space using laser beams (such as “optical tweezers” and “optical lattices”). What can one do using these tools? One possibility is arranging the atoms in a regular array.
Why people find it interesting? It was found that such systems have properties much different than clouds of atoms randomly flying around. The lattice structure changes how the atoms emit and absorb light. This is because light emitted from different atoms can interfere, and a regular structure of array works like a diffraction grating. This happens especially if the distance between atoms is smaller than one wavelength.
For example, a 1D chain of atoms in a certain state emits light only on its ends. And a 2D array can act as a perfect mirror (for certain wavelength), even though it is only one atom thin.
It was theoretically shown that these effects can be used to boost the efficiency of optical quantum devices such as memories and gates, which may be used in the future for a “quantum internet” and quantum computers.
#Physics #Science #Quantum #QuantumOptics #atoms #CondensedMatter #CondMat
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New general law governs fracture energy of networks across materials and length scales
https://techxplore.com/news/2025-01-general-law-fracture-energy-networks.html
Tech Xplore · New general law governs fracture energy of networks across materials and length scales
Anyons in spin liquids
To see how anyons can arise in topological orders, one can look again on the simplified picture of the Z2 spin liquid (see the previous post: https://fediscience.org/@quinto/113465683021157305). Anyons can be created on the top of the spin liquid by altering the singlet pattern.
First, we can break one singlet bond into two spins, one up and one down, which can move freely throughout the pattern by rearranging the singlets. The two spins can be thought of as (quasi)particles called spinons.
By the way, spinons can also be created by flipping a spin. In a spin liquid ground state, we have as many up spins as down spins, so all of them can be paired into singlets. But if we flip one of, say, down spins, we have *two* up spins that cannot be paired – two spinons. One flipped spin somehow turns into two quasiparticles. This is known as “fractionalization”.
Secondly, we can do something more complicated. We can draw a line intersecting some bonds. Then, in the sum over all singlet configurations, we put a plus if the line intersect an even number of singlets and minus if this number is odd. The ends of the line are quasiparticles called visons. It does not matter how we draw the line – it only matters where it starts and ends.
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#physics #science #CondensedMatter #CondMat #TopologicalOrder #Anyons
Yesterday Charlie-Ray Mann gave a talk as a part of the "Many-Body Quantum Optics" program at KITP. Charlie is a postdoc working in the same group as me. Part of presented work (2D numerics which is not directly referenced) was done by me within the QUINTO project. You can listen to the recording of the talk here: https://online.kitp.ucsb.edu/online/mbqoptics24/mann/
We are now in Santa Barbara, California, for a program “Many-body quantum optics” at Kavli Institute for Theoretical Physics. The program is co-organized by the supervisor of QUINTO, prof Darrick Chang, and is aimed at fostering collaborations between the condensed matter and quantum optics researchers. We already had a couple of interesting discussions and are looking forward to more!
Spin liquid
As an example of how a topological order can look like, one can look at simplified picture of so-called Z2 spin liquid. This type of topological order is postulated to occur in some “frustrated magnets”.
#physics #TopologicalOrder #science #CondensedMatter #CondMat
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Interactions and order
Interactions can do many things, but one of the most important effects is causing the system to order. A simple example is a magnet. As I mentioned in the previous post, electrons have a quantum property called “spin”. In a crude, cartoon picture, it means that they can rotate around an axis (say, the “z” axis) clockwise or anticlockwise, which is represented by up and down arrow.
#physics #CondensedMatter #CondMat #science #topology #quantum #QuantumComputing
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QUNITO and condensed matter physics
Condensed matter physics study systems such as crystals, systems often containing many electrons (a macroscopic piece of any material will contain about 10^23 of them). Electrons, unlike photons, do interact with each other, and in some settings, this interaction becomes really important.
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#Physics #CondensedMatter #CondMat #science
What is QUINTO about?
For many years, physicists studied interaction between atoms and light – be it single atoms, or clouds containing many of them. A relatively new setup is an array of atoms – a system where atoms are held in place e.g. by so-called “optical tweezers” and arranged in a regular, periodic lattice, quite similar to a crystal.
#Physics #Science #CondensedMatter #CondMat #QuantumOptics
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Hi!
We are conducting a research project on the intersection of quantum optics and condensed matter. We study what happens if an ordered array of atoms absorbs many photons, thus becoming a complex system of many interacting particles. We want to find and exploit analogies between such systems and so-called topological orders, and build a “bridge” between the two fields of physics.
#introduction #Physics #CondensedMatter #CondMat #QuantumOptics #TopologicalOrder #ManyBody #ColdAtoms
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Today's #arXivsummary: https://arxiv.org/abs/2311.06350 by Romen et. al. Authors investigate deconfined quantum critical points in the long-range, anisotropic Heisenberg chain. Model undergoes a continuous phase transition from valence bond solid to an antiferromagnet. Long-range interactions are irrelevant & transition is well described by a double frequency sine-Gordon model. #CondMat #arXiv_2311_06350
arXiv.orgDeconfined Quantum Criticality in the long-range, anisotropic Heisenberg ChainDeconfined quantum criticality describes continuous phase transitions that are not captured by the Landau-Ginzburg paradigm. Here, we investigate deconfined quantum critical points in the long-range, anisotropic Heisenberg chain. With matrix product state simulations, we show that the model undergoes a continuous phase transition from a valence bond solid to an antiferromagnet. We extract the critical exponents of the transition and connect them to an effective field theory obtained from bosonization techniques. We show that beyond stabilizing the valance bond order, the long-range interactions are irrelevant and the transition is well described by a double frequency sine-Gordon model. We propose how to realize and probe deconfined quantum criticality in our model with trapped-ion quantum simulators.
Today's #arXivsummary: https://arxiv.org/abs/2311.04266 by Radzihovsky. Author points out a simple and generic mechanism for a thermally-driven reentrant supersolidity. Mechanism reduces to a re-enterant low-temperature normal-superfluid transition. #CondMat #arXiv_2311_04266
arXiv.orgReentrant supersolidityA "supersolid" -- a crystal that exhibits an off-diagonal long-range order and a superflow -- has been a subject of much research since its first proposal [Andreev and Lifshitz 1969], but has not been realized as a ground state of short-range interacting bosons in a continuum. In this note I point out a simple and generic mechanism for a thermally-driven reentrant supersolidity, and discuss challenges of experimental realization of this idea. In the limit of bosons in a periodic potential, this mechanism reduces to a {\em reentrant} low-temperature normal-superfluid transition, that should be accessible to simulations and in current experiments on bosonic atoms in an optical periodic potential.
Today's #arXivsummary: https://arxiv.org/abs/2311.02155 by Pak et. al. Authors show that the PT-symmetry stabilizes the Hopf invariant in the Hopf insulator even in the presence of non-Hermiticity. Zak phase remains quantized. #CondMat #arXiv_2311_02155
arXiv.orgPT-symmetric Non-Hermitian Hopf MetalHopf insulator is a representative class of three-dimensional topological insulators beyond the standard topological classification methods based on K-theory. In this letter, we discover the metallic counterpart of the Hopf insulator in the non-Hermitian systems. While the Hopf invariant is not a stable topological index due to the additional non-Hermitian degree of freedom, we show that the PT-symmetry stabilizes the Hopf invariant even in the presence of the non-Hermiticity. In sharp contrast to the Hopf insulator phase in the Hermitian counterpart, we discover an interesting result that the non-Hermitian Hopf bundle exhibits the topologically protected non-Hermitian degeneracy, characterized by the two-dimensional surface of exceptional points. Despite the non-Hermiticity, the Hopf metal has the quantized Zak phase, which results in bulk-boundary correspondence by showing drumhead-like surface states at the boundary. Finally, we show that, by breaking PT-symmetry, the nodal surface deforms into the knotted exceptional lines. Our discovery of the Hopf metal phase firstly confirms the existence of the non-Hermitian topological phase outside the framework of the standard topological classifications.
Today's #arXivsummary: https://arxiv.org/abs/2310.11236 by Misawa. Author's work suggests that quasiparticles in the normal state of high-Tc cuprate superconductors behave as a 3D Fermi liquid. Logarithmic formula as a function of T emerges in transport quantities and thermodynamics results from quasiparticle interactions. #CondMat #arXiv_2310_11236
arXiv.orgThe 3-dimensional Fermi liquid description for the normal state of cuprate superconductorsThe quasiparticles in the normal state of cuprate superconductors have been shown to behave universally as a 3-dimensional Fermi liquid. Because of interactions and the presence of the Fermi surfaces (or Fermi energies), the quasiparticle energy contains, as a function of the momentum $\boldmath{p}$, a term of the form $(p-p_0)^3 \ln ( | p-p_0 | / p_0 )$, where $p = | \boldmath{p} |$ and $p_0$ is the Fermi momentum. The electronic specific heat coefficient $γ(T)$, electrical resistivity, Hall coefficient and thermoelectric power divided by temperature $T$, follow the logarithmic formula $a - b T^2 \ln ( T/T^*) $, $a$, $b$, and $T^*$ being constant. Singularities in the Landau $f$-function produce the $T^2 \ln T$ dependence of the magnetic susceptibility $χ(T)$, and Knight shift, which gives rise to the phenomenon of the susceptibility maximum. The logarithmic $T$-dependence of the transport properties arises exclusively from the impurity scattering in 3-dimensional (3D) systems, but does not from the electron-electron scattering in 2D systems. The above logarithmic formula has been shown to explain universally the experimental data for the normal state of all cuprate superconductors. The decrease of $γ(T)$ or $χ(T)$ with decreasing $T$ is not due to the appearance of pseudogap or spin gap but due to its $T^2 \ln T$ variation.
Today's #arXivsummary: https://arxiv.org/abs/2310.09324 by Sun. Authors show that an indirect exchange interaction between spin impurities can be controlled by a dissipationless supercurrent with just a conventional superconductor and two spin impurities placed on its surface. #CondMat #arXiv_2310_09324
arXiv.orgSupercurrent-induced spin switching via indirect exchange interactionLocalized spins of single atoms adsorbed on surfaces have been proposed as building blocks for spintronics and quantum computation devices. However, identifying a way to achieve current-induced switching of spins with very low dissipation is an outstanding challenge with regard to practical applications. Here, we show that the indirect exchange interaction between spin impurities can be controlled by a dissipationless supercurrent. All that is required is a conventional superconductor and two spin impurities placed on its surface. No triplet Cooper pairs or exotic material choices are needed. This finding provides a new and accessible way to achieve the long-standing goal of supercurrent-induced spin switching.
Today's arXivsummary: https://arxiv.org/abs/2310.09063, by Witt et. al. Multi-orbital model of alkali-doped fullerides (A3C60) developed using Dynamical Mean-Field Theory, which is utilized to show how proximity of superconductivity, Jahn-Teller metallic, and Mott-localized states impact the superconducting coherence, order parameter stiffness, & critical temperature. Localized superconducting regime with very short coherence length. #CondMat #arXiv_2310_09063
arXiv.orgBypassing the lattice BCS-BEC crossover in strongly correlated superconductors: resilient coherence from multiorbital physicsSuperconductivity emerges from the spatial coherence of a macroscopic condensate of Cooper pairs. Increasingly strong binding and localization of electrons into these pairs compromises the condensate's phase stiffness, thereby limiting critical temperatures -- a phenomenon known as the BCS-BEC crossover in lattice systems. In this study, we demonstrate enhanced superconductivity in a multiorbital model of alkali-doped fullerides (A$_3$C$_{60}$) that goes beyond the limits of the lattice BCS-BEC crossover. We identify that the interplay of strong correlations and multiorbital effects results in a localized superconducting state characterized by a short coherence length but robust stiffness and a domeless rise in critical temperature with increasing pairing interaction. To derive these insights, we introduce a new theoretical framework allowing us to calculate the fundamental length scales of superconductors, namely the coherence length ($ξ_0$) and the London penetration depth ($λ_{\mathrm{L}}$), even in presence of strong electron correlations.
Today's #arXivsummary: https://arxiv.org/abs/2310.07978 by Chen et. al. Authors study Anderson localization in disordered tight-binding models on hyperbolic lattices. Numerically show the existence of an Anderson localization transition on the {8,3} & {8,8} lattices. #CondMat #arXiv_2310_07978
arXiv.orgAnderson localization transition in disordered hyperbolic latticesWe study Anderson localization in disordered tight-binding models on hyperbolic lattices. Such lattices are geometries intermediate between ordinary two-dimensional crystalline lattices, which localize at infinitesimal disorder, and Bethe lattices, which localize at strong disorder. Using state-of-the-art computational group theory methods to create large systems, we approximate the thermodynamic limit through appropriate periodic boundary conditions and numerically demonstrate the existence of an Anderson localization transition on the $\{8,3\}$ and $\{8,8\}$ lattices. We find unusually large critical disorder strengths, determine critical exponents, and observe a strong finite-size effect in the level statistics.