Showing papers on "Explicit symmetry breaking published in 2017"
TL;DR: In this paper, the authors present the experimental observation of a discrete time crystal in an interacting spin chain of trapped atomic ions and apply a periodic Hamiltonian to the system under many-body localization conditions, and observe a subharmonic temporal response that is robust to external perturbations.
Abstract: Spontaneous symmetry breaking is a fundamental concept in many areas of physics, including cosmology, particle physics and condensed matter. An example is the breaking of spatial translational symmetry, which underlies the formation of crystals and the phase transition from liquid to solid. Using the analogy of crystals in space, the breaking of translational symmetry in time and the emergence of a 'time crystal' was recently proposed, but was later shown to be forbidden in thermal equilibrium. However, non-equilibrium Floquet systems, which are subject to a periodic drive, can exhibit persistent time correlations at an emergent subharmonic frequency. This new phase of matter has been dubbed a 'discrete time crystal'. Here we present the experimental observation of a discrete time crystal, in an interacting spin chain of trapped atomic ions. We apply a periodic Hamiltonian to the system under many-body localization conditions, and observe a subharmonic temporal response that is robust to external perturbations. The observation of such a time crystal opens the door to the study of systems with long-range spatio-temporal correlations and novel phases of matter that emerge under intrinsically non-equilibrium conditions.
970 citations
TL;DR: In this article, the authors studied the effects of short-range interactions on a generalized three-dimensional Weyl semimetal, where the band touching points act as the (anti)monopoles of Abelian Berry curvature of strength.
Abstract: We study the effects of short-range interactions on a generalized three-dimensional Weyl semimetal, where the band touching points act as the (anti)monopoles of Abelian Berry curvature of strength $n$. We show that any local interaction has a negative scaling dimension $\ensuremath{-}2/n$. Consequently, all Weyl semimetals are stable against weak short-range interactions. For sufficiently strong interactions, we demonstrate that the Weyl semimetal either undergoes a first-order transition into a band insulator or a continuous transition into a symmetry breaking phase. A translational symmetry breaking axion insulator and a rotational symmetry breaking semimetal are two prominent candidates for the broken symmetry phase. At the one-loop order, the correlation length exponent for continuous transitions is $\ensuremath{
u}=n/2$, indicating their non-Gaussian nature for any $ng1$. We also discuss the scaling of the thermodynamic and transport quantities in general Weyl semimetals as well as inside broken symmetry phases.
118 citations
TL;DR: The findings therefore provide opportunities for creating spin-textured states and suggest routes to interfacial control of inversion-symmetry breaking in designer heterostructures of oxides and other material classes.
Abstract: Engineering and enhancing the breaking of inversion symmetry in solids-that is, allowing electrons to differentiate between 'up' and 'down'-is a key goal in condensed-matter physics and materials science because it can be used to stabilize states that are of fundamental interest and also have potential practical applications. Examples include improved ferroelectrics for memory devices and materials that host Majorana zero modes for quantum computing. Although inversion symmetry is naturally broken in several crystalline environments, such as at surfaces and interfaces, maximizing the influence of this effect on the electronic states of interest remains a challenge. Here we present a mechanism for realizing a much larger coupling of inversion-symmetry breaking to itinerant surface electrons than is typically achieved. The key element is a pronounced asymmetry of surface hopping energies-that is, a kinetic-energy-coupled inversion-symmetry breaking, the energy scale of which is a substantial fraction of the bandwidth. Using spin- and angle-resolved photoemission spectroscopy, we demonstrate that such a strong inversion-symmetry breaking, when combined with spin-orbit interactions, can mediate Rashba-like spin splittings that are much larger than would typically be expected. The energy scale of the inversion-symmetry breaking that we achieve is so large that the spin splitting in the CoO2- and RhO2-derived surface states of delafossite oxides becomes controlled by the full atomic spin-orbit coupling of the 3d and 4d transition metals, resulting in some of the largest known Rashba-like spin splittings. The core structural building blocks that facilitate the bandwidth-scaled inversion-symmetry breaking are common to numerous materials. Our findings therefore provide opportunities for creating spin-textured states and suggest routes to interfacial control of inversion-symmetry breaking in designer heterostructures of oxides and other material classes.
116 citations
TL;DR: In this paper, a series of perturbations on the SYK model were studied, and it was shown that changing the sign of one of these four-fermion perturbation leads to a continuous chaotic-non-chaotic quantum phase transition of the system accompanied by a spontaneous time-reversal symmetry breaking.
Abstract: We study a series of perturbations on the Sachdev-Ye-Kitaev (SYK) model. We show that the maximal chaotic non-Fermi-liquid phase described by the ordinary $q=4$ SYK model has marginally relevant or irrelevant (depending on the sign of the coupling constants) four-fermion perturbations allowed by symmetry. Changing the sign of one of these four-fermion perturbations leads to a continuous chaotic-nonchaotic quantum phase transition of the system accompanied by a spontaneous time-reversal symmetry breaking. Starting with the ${\mathrm{SYK}}_{q}$ model with a $q$-fermion interaction, similar perturbations can lead to a series of new fixed points with continuously varying exponents.
108 citations
TL;DR: In this article, the authors generalized the concept of symmetry from groups to non-Abelian groups by enlarging the notion of symmetry defined by groups to those defined by unitary fusion categories, and studied the axiomatization of two-dimensional quantum field theories whose symmetry is given by a category.
Abstract: It is well-known that if we gauge a $\mathbb{Z}_n$ symmetry in two dimensions, a dual $\mathbb{Z}_n$ symmetry appears, such that re-gauging this dual $\mathbb{Z}_n$ symmetry leads back to the original theory. We describe how this can be generalized to non-Abelian groups, by enlarging the concept of symmetries from those defined by groups to those defined by unitary fusion categories. We will see that this generalization is also useful when studying what happens when a non-anomalous subgroup of an anomalous finite group is gauged: for example, the gauged theory can have non-Abelian group symmetry even when the original symmetry is an Abelian group. We then discuss the axiomatization of two-dimensional topological quantum field theories whose symmetry is given by a category. We see explicitly that the gauged version is a topological quantum field theory with a new symmetry given by a dual category.
87 citations
TL;DR: The probability distribution of a current flowing through a diffusive system connected to a pair of reservoirs at its two ends is studied, and an exact Landau theory which captures the different singular behaviors is derived.
Abstract: We study the probability distribution of a current flowing through a diffusive system connected to a pair of reservoirs at its two ends. Sufficient conditions for the occurrence of a host of possible phase transitions both in and out of equilibrium are derived. These transitions manifest themselves as singularities in the large deviation function, resulting in enhanced current fluctuations. Microscopic models which implement each of the scenarios are presented, with possible experimental realizations. Depending on the model, the singularity is associated either with a particle-hole symmetry breaking, which leads to a continuous transition, or in the absence of the symmetry with a first-order phase transition. An exact Landau theory which captures the different singular behaviors is derived.
85 citations
TL;DR: In this paper, the spontaneous breaking of translation and conformal symmetries is analyzed by introducing in a CFT a complex scalar operator that acquires a spatially dependent expectation value, inspired by the holographic Q-lattice.
Abstract: We analyze the concomitant spontaneous breaking of translation and conformal symmetries by introducing in a CFT a complex scalar operator that acquires a spatially dependent expectation value. The model, inspired by the holographic Q-lattice, provides a privileged setup to study the emergence of phonons from a spontaneous translational symmetry breaking in a conformal field theory and offers valuable hints for the treatment of phonons in QFT at large. We first analyze the Ward identity structure by means of standard QFT techniques, considering both spontaneous and explicit symmetry breaking. Next, by implementing holographic renormalization, we show that the same set of Ward identities holds in the holographic Q-lattice. Eventually, relying on the holographic and QFT results, we study the correlators realizing the symmetry breaking pattern and how they encode information about the low-energy spectrum.
80 citations
TL;DR: In this article, the authors propose a simple prescription which provides an origin of the Peccei-Quinn (PQ) symmetry, which can be implemented in many conventional models with the PQ symmetry.
68 citations
TL;DR: In this article, the authors investigated the spontaneous breaking of a discrete symmetry in a driven-dissipative Bose-Hubbard lattice in the presence of two-photon coherent driving.
Abstract: We investigate the occurrence of a phase transition, characterized by the spontaneous breaking of a discrete symmetry, in a driven-dissipative Bose-Hubbard lattice in the presence of two-photon coherent driving. The driving term does not lift the original $\text{U}(1)$ symmetry completely and a discrete ${\mathbb{Z}}_{2}$ symmetry is left. When driving the bottom of the Bose-Hubbard band, a mean-field analysis of the steady state reveals a second-order transition from a symmetric phase to a quasicoherent state with a finite expectation value of the Bose field. For larger driving frequency, the phase diagram shows a third region, where both phases are stable and the transition becomes of first order.
64 citations
TL;DR: In this paper, the large gauge transformations of massless higher-spin fields in four-dimensional Minkowski space were studied and the existence of an infinite-dimensional asymptotic symmetry algebra was observed.
Abstract: We study the large gauge transformations of massless higher-spin fields in four-dimensional Minkowski space. Upon imposing suitable fall-off conditions, providing higher-spin counterparts of the Bondi gauge, we observe the existence of an infinite-dimensional asymptotic symmetry algebra. The corresponding Ward identities can be held responsible for Weinberg’s factorisation theorem for amplitudes involving soft particles of spin greater than two.
64 citations
TL;DR: Time crystals are states of matter that spontaneously break time translation symmetry as discussed by the authors, and they have been used to define Wigner symmetries and order parameters for many-body localized spin glass/Floquet time crystals.
Abstract: Time crystals are proposed states of matter that spontaneously break time translation symmetry. Despite much recent interest, there is no settled definition for such states and existing definitions only tangentially refer to the well-established foundations of spontaneous symmetry breaking. We offer a definition of time crystals, which treats time translation much like any other symmetry and follows the traditional recipe for defining Wigner symmetries and order parameters. Using our definition, we find: (i) systems with time independent Hamiltonians should not exhibit time translation symmetry breaking, and (ii) the many-body localized $\ensuremath{\pi}$ spin glass/Floquet time crystal can be viewed as breaking both a global internal symmetry and the time translation symmetry, as befits the two aspects of its name.
TL;DR: A general, numerically motivated approach to the construction of symmetry-adapted basis functions for solving ro-vibrational Schrödinger equations based on the property of the Hamiltonian operator to commute with the complete set of symmetry operators and, hence, to reflect the symmetry of the system.
Abstract: We present a general, numerically motivated approach to the construction of symmetry-adapted basis functions for solving ro-vibrational Schrodinger equations. The approach is based on the property of the Hamiltonian operator to commute with the complete set of symmetry operators and, hence, to reflect the symmetry of the system. The symmetry-adapted ro-vibrational basis set is constructed numerically by solving a set of reduced vibrational eigenvalue problems. In order to assign the irreducible representations associated with these eigenfunctions, their symmetry properties are probed on a grid of molecular geometries with the corresponding symmetry operations. The transformation matrices are reconstructed by solving overdetermined systems of linear equations related to the transformation properties of the corresponding wave functions on the grid. Our method is implemented in the variational approach TROVE and has been successfully applied to many problems covering the most important molecular symmetry gro...
TL;DR: By using the symmetry reduction method to the enlarged systems, many explicit interaction solutions among different types of solutions such as solitary waves, rational solutions, Painleve II solutions are given and some special concrete soliton-cnoidal interaction solutions are analyzed both in analytical and graphical ways.
TL;DR: In this paper, the spontaneous breaking of continuous space translation symmetry in the process of space crystal formation was studied in ultracold atomic gases, where the symmetry breaking can take place if the system is prepared in an excited eigenstate.
Abstract: In analogy to spontaneous breaking of continuous space translation symmetry in the process of space crystal formation, it was proposed that spontaneous breaking of continuous time translation symmetry could lead to time crystal formation. In other words, a time-independent system prepared in the energy ground state is expected to reveal periodic motion under infinitely weak perturbation. In the case of the system proposed originally by Wilczek, spontaneous breaking of time translation symmetry cannot be observed if one starts with the ground state. We point out that the symmetry breaking can take place if the system is prepared in an excited eigenstate. The latter can be realized experimentally in ultracold atomic gases. We simulate the process of the spontaneous symmetry breaking due to measurements of particle positions and analyze the lifetime of the resulting symmetry broken state.
TL;DR: By characterizing the collective motion of the ion crystals, this experiment identifies homogeneous electric fields as the dominant symmetry-breaking mechanism at this energy scale and predicts that, with only a ten-ion ring, uncompensated homogeneous fields will not break the translational symmetry of the rotational ground state.
Abstract: We crystallize up to 15 ^{40}Ca^{+} ions in a ring with a microfabricated silicon surface Paul trap Delocalization of the Doppler laser-cooled ions shows that the translational symmetry of the ion ring is preserved at millikelvin temperatures By characterizing the collective motion of the ion crystals, we identify homogeneous electric fields as the dominant symmetry-breaking mechanism at this energy scale With increasing ion numbers, such detrimental effects are reduced We predict that, with only a ten-ion ring, uncompensated homogeneous fields will not break the translational symmetry of the rotational ground state This experiment opens a door towards studying quantum many-body physics with translational symmetry at the single-particle level
TL;DR: In this paper, a scalar clockwork mechanism is proposed to generate hierarchies among parameters in quantum field theories, characterized by a very specific pattern of spontaneous and explicit symmetry breaking, and the presence of new light states referred to as ''gears''.
Abstract: The clockwork mechanism has recently been proposed as a natural way to generate hierarchies among parameters in quantum field theories. The mechanism is characterized by a very specific pattern of spontaneous and explicit symmetry breaking, and the presence of new light states referred to as ``gears.'' In this paper we begin by investigating the self-interactions of these gears in a scalar clockwork model and find a paritylike selection rule at all orders in the fields. We then proceed to investigate how the clockwork mechanism can be realized in five-dimensional linear dilaton models from the spontaneous symmetry breaking of a complex bulk scalar field. We also discuss how the clockwork mechanism is manifest in the scalar components of five-dimensional gauge theories in the linear dilaton model, and build their four-dimensional deconstructed analogue. Finally we discuss attempts at building both four-dimensional and five-dimensional realizations of a non-Abelian scalar clockwork mechanism, where in the latter we consider scenarios in which the Goldstone bosons arise from five-dimensional scalar and five-dimensional gauge fields.
TL;DR: The findings demonstrate that nonlinear propagation can manifest features typical of spin-glasses and provide a novel platform for testing so-far unexplored fundamental physical theories for complex systems.
Abstract: A landmark of statistical mechanics, spin-glass theory describes critical phenomena in disordered systems that range from condensed matter to biophysics and social dynamics. The most fascinating concept is the breaking of replica symmetry: identical copies of the randomly interacting system that manifest completely different dynamics. Replica symmetry breaking has been predicted in nonlinear wave propagation, including Bose-Einstein condensates and optics, but it has never been observed. Here, we report the experimental evidence of replica symmetry breaking in optical wave propagation, a phenomenon that emerges from the interplay of disorder and nonlinearity. When mode interaction dominates light dynamics in a disordered optical waveguide, different experimental realizations are found to have an anomalous overlap intensity distribution that signals a transition to an optical glassy phase. The findings demonstrate that nonlinear propagation can manifest features typical of spin-glasses and provide a novel platform for testing so-far unexplored fundamental physical theories for complex systems. Replica symmetry breaking describes identical copies of a randomly interacting system exhibiting different dynamics. Here, Pierangeli et al. observe this critical phenomenon in the optical wave propagation inside a disordered nonlinear waveguide.
TL;DR: In this article, a massive Carroll-Field-Jackiw photon term in the Lagrangian is extracted and the effective mass is proportional to the breaking vector and moderately dependent on the direction of observation, leading to a photon mass upper limit of 10−19eVor 2 ×10−55kg.
TL;DR: Zhao et al. as discussed by the authors showed that in the absence of translational symmetry breaking or topological order, these conventional order parameters cannot explain the gap in the charged fermion excitation spectrum in the antinodal region.
Abstract: Numerous experiments have reported discrete symmetry breaking in the high-temperature pseudogap phase of the hole-doped cuprates, including breaking of one or more of lattice rotation, inversion, and time-reversal symmetries. In the absence of translational symmetry breaking or topological order, these conventional order parameters cannot explain the gap in the charged fermion excitation spectrum in the antinodal region. Zhao et al. [L. Zhao, D. H. Torchinsky, H. Chu, V. Ivanov, R. Lifshitz, R. Flint, T. Qi, G. Cao, and D. Hsieh, Nat. Phys. 12, 32 (2016)] and Jeong et al. [J. Jeong, Y. Sidis, A. Louat, V. Brouet, and P. Bourges, Nat. Commun. 8, 15119 (2017)] have also reported inversion and time-reversal symmetry breaking in insulating ${\mathrm{Sr}}_{2}{\mathrm{IrO}}_{4}$ similar to that in the metallic cuprates, but coexisting with N\'eel order. We extend an earlier theory of topological order in insulators and metals, in which the topological order combines naturally with the breaking of these conventional discrete symmetries. We find translationally invariant states with topological order coexisting with both Ising-nematic order and spontaneous charge currents. The link between the discrete broken symmetries and the topological-order-induced pseudogap explains why the broken symmetries do not survive in the confining phases without a pseudogap at large doping. Our theory also connects to the O(3) nonlinear sigma model and ${\text{CP}}^{1}$ descriptions of quantum fluctuations of the N\'eel order. In this framework, the optimal doping criticality of the cuprates is primarily associated with the loss of topological order.
TL;DR: In this paper, the authors show that the firewall problem can be solved by assuming an extra local symmetry, conformal invariance, spontaneously broken by the vacuum, in a way similar to the Brout-Englert-Higgs mechanism.
Abstract: The black hole information problem and the firewall problem can be addressed by assuming an extra local symmetry: conformal invariance. It must be an exact symmetry, spontaneously broken by the vacuum, in a way similar to the Brout–Englert–Higgs (BEH) mechanism. We note how this symmetry formally removes the horizon and the singularity inside black holes. For the Standard Model this symmetry is severely restrictive, demanding all coupling constants, masses and even the cosmological constant to be computable, in principle. Finally, this symmetry suggests that the Weyl action (the square of the Weyl curvature) should be added to the Einstein–Hilbert action. The ensuing indefinite metric states are briefly studied, and we conclude with some remarks concerning the interpretation of quantum mechanics.
TL;DR: In this article, mixed symmetry superconducting phases in Dirac materials in the odd parity channel were considered, where pseudoscalar and vector order parameters can coexist due to their similar critical temperatures when attractive interactions are of finite range.
Abstract: We consider mixed symmetry superconducting phases in Dirac materials in the odd parity channel, where pseudoscalar and vector order parameters can coexist due to their similar critical temperatures when attractive interactions are of finite range. We show that the coupling of these order parameters to unordered magnetic dopants favors the condensation of novel time-reversal symmetry breaking (TRSB) phases, characterized by a condensate magnetization, rotation symmetry breaking, and simultaneous ordering of the dopant moments. We find a rich phase diagram of mixed TRSB phases characterized by peculiar bulk quasiparticles, with Weyl nodes and nodal lines, and distinctive surface states. These findings are consistent with recent experiments on Nb$_x$Bi$_2$Se$_3$ that report evidence of point nodes, nematicity, and TRSB superconductivity induced by Nb magnetic moments.
TL;DR: In this article, it was shown that the addition of positive mass-squared terms to asymptotically safe gauge-Yukawa theories with perturbative UV fixed points leads to calculable radiative symmetry breaking in the IR.
Abstract: It is shown that the addition of positive mass-squared terms to asymptotically safe gauge-Yukawa theories with perturbative UV fixed points leads to calculable radiative symmetry breaking in the IR. This phenomenon, and the multiplicative running of the operators that lies behind it, is akin to the radiative symmetry breaking that occurs in the supersymmetric standard model.
TL;DR: In this paper, the scale-invariant inflationary model is considered in the Jordan frame and the symmetry is spontaneously broken after an arbitrarily long inflationary period and a fundamental mass scale is generated.
Abstract: We consider the scale-invariant inflationary model studied in Rinaldi and Vanzo (Phys Rev D 94: 024009, 2016). The Lagrangian includes all the scale-invariant operators that can be built with combinations of \(R, R^{2}\) and one scalar field. The equations of motion show that the symmetry is spontaneously broken after an arbitrarily long inflationary period and a fundamental mass scale is generated. Upon symmetry breaking, and in the Jordan frame, both Hubble function and the scalar field undergo damped oscillations that can eventually amplify Standard Model fields and reheat the Universe. In the present work, we study in detail inflation and the reheating mechanism of this model in the Einstein frame and we compare some of the results with the latest observational data.
TL;DR: The neutrino μ-τ reflection symmetry has been attracting a lot of attention as it predicts the interesting results θ − 23 = π/4 and δ = ±π/2.
Abstract: The neutrino μ-τ reflection symmetry has been attracting a lot of attention as it predicts the interesting results θ
23 = π/4 and δ = ±π/2. But it is reasonable to consider breakings of such a symmetry either from the theoretical considerations or on the basis of experimental results. We thus perform a systematic study for the possible symmetry-breaking patterns and their implications for the mixing parameters. The general treatment is applied to some specific symmetry breaking arising from the renormalization group effects for illustration.
TL;DR: The notion of symmetry enriched topological (SET) phases was introduced in this paper, where the symmetry properties of the anyons, such as their fractional charges, or the way that different anyons are permuted by the symmetry, are considered.
Abstract: The hallmark of a two-dimensional (2d) topologically ordered phase is the existence of deconfined ``anyon'' excitations that have exotic braiding and exchange statistics, different from those of ordinary bosons or fermions. As opposed to conventional Landau-Ginzburg-Wilson phases, which are classified on the basis of the spontaneous breaking of an underlying symmetry, topologically ordered phases, such as those occurring in the fractional quantum Hall effect, are absolutely stable, not requiring any such symmetry. Recently, though, it has been realized that symmetries, which may still be present in such systems, can give rise to a host of new, distinct, many-body phases, all of which share the same underlying topological order. These ``symmetry enriched'' topological (SET) phases are distinguished not on the basis of anyon braiding statistics alone, but also by the symmetry properties of the anyons, such as their fractional charges, or the way that different anyons are permuted by the symmetry. Thus a useful approach to classifying SETs is to determine all possible such symmetry actions on the anyons that are algebraically consistent with the anyon statistics. Remarkably, however, there exist symmetry actions that, despite being algebraically consistent, cannot be realized in any physical system, and hence do not lead to valid 2d SETs. One class of such ``anomalous'' SETs, characterized by certain disallowed symmetry fractionalization patterns, finds a physical interpretation as an allowed surface state of certain three-dimensional (3d) short-range entangled phases, but another, characterized by some seemingly valid but anomalous permutation actions of the symmetry on the anyons and encoded in an ${H}^{3}(G,\mathcal{A})$ group cohomology class, has so far eluded a physical interpretation. In this work, we find a way to physically realize these anomalously permuting SETs at the surfaces of certain 3d long-range entangled phases, expanding our understanding of general anomalous SETs in two dimensions.
TL;DR: In this paper, the UV divergences of DBI, conformal DBI and A-V theory are computed to verify the exactness of type (II) soft theorems, while type (I) are shown to be broken and the soft modifying higher-dimensional operators are identified.
Abstract: Soft behaviours of S-matrix for massless theories reflect the underlying symmetry principle that enforces its masslessness As an expansion in soft momenta, sub-leading soft theorems can arise either due to (I) unique structure of the fundamental vertex or (II) presence of enhanced broken-symmetries While the former is expected to be modified by infrared or ultraviolet divergences, the latter should remain exact to all orders in perturbation theory Using current algebra, we clarify such distinction for spontaneously broken (super) Poincar\'e and (super) conformal symmetry We compute the UV divergences of DBI, conformal DBI, and A-V theory to verify the exactness of type (II) soft theorems, while type (I) are shown to be broken and the soft-modifying higher-dimensional operators are identified As further evidence for the exactness of type (II) soft theorems, we consider the alpha' expansion of both super and bosonic open strings amplitudes, and verify the validity of the translation symmetry breaking soft-theorems up to O(alpha'^6) Thus the massless S-matrix of string theory "knows" about the presence of D-branes
TL;DR: It is found that although electronic carriers are immediately delocalized, the crystal symmetry remains initially frozen—as witnessed by time-delayed suppression of zone-folded Ni–O bending modes acting as a fingerprint of lattice symmetry.
Abstract: The ability to probe symmetry-breaking transitions on their natural time scales is one of the key challenges in nonequilibrium physics. Stripe ordering represents an intriguing type of broken symmetry, where complex interactions result in atomic-scale lines of charge and spin density. Although phonon anomalies and periodic distortions attest the importance of electron-phonon coupling in the formation of stripe phases, a direct time-domain view of vibrational symmetry breaking is lacking. We report experiments that track the transient multi-terahertz response of the model stripe compound La1.75Sr0.25NiO4, yielding novel insight into its electronic and structural dynamics following an ultrafast optical quench. We find that although electronic carriers are immediately delocalized, the crystal symmetry remains initially frozen-as witnessed by time-delayed suppression of zone-folded Ni-O bending modes acting as a fingerprint of lattice symmetry. Longitudinal and transverse vibrations react with different speeds, indicating a strong directionality and an important role of polar interactions. The hidden complexity of electronic and structural coupling during stripe melting and formation, captured here within a single terahertz spectrum, opens new paths to understanding symmetry-breaking dynamics in solids.
TL;DR: In this article, the authors describe a hidden conformal symmetry of the second Randall-Sundrum model (RS2) which can be used to localize fermions of both chiralities.
TL;DR: In this article, a relativistic scalar particle subject to a scalar potential proportional to the inverse of the radial distance was analyzed under the effects of the violation of the Lorentz symmetry.
Abstract: Based on models of confinement of quarks, we analyse a relativistic scalar particle subject to a scalar potential proportional to the inverse of the radial distance and under the effects of the violation of the Lorentz symmetry. We show that the effects of the Lorentz symmetry breaking can induced a harmonic-type potential. Then, we solve the Klein-Gordon equation analytically and discuss the influence of the background of the violation of the Lorentz symmetry on the relativistic energy levels.
TL;DR: In this paper, the authors introduce two-and one-dimensional (2D and 1D) systems of two linearly coupled Gross-Pitaevskii equations with the cubic self-attraction and harmonic-oscillator (HO) trapping potential in each GPE.
Abstract: We introduce two- and one-dimensional (2D and 1D) systems of two linearly coupled Gross-Pitaevskii equations (GPEs) with the cubic self-attraction and harmonic-oscillator (HO) trapping potential in each GPE. The system models a Bose-Einstein condensate with a negative scattering length, loaded in a double-pancake trap, combined with the in-plane HO potential. In addition to that, the 1D version applies to the light transmission in a dual-core waveguide with the Kerr nonlinearity and in-core confinement represented by the HO potential. The subject of the analysis is spontaneous symmetry breaking in 2D and 1D ground-state (GS, alias fundamental) modes, as well as in 2D vortices and 1D dipole modes. (The latter ones do not exist without the HO potential.) By means of the variational approximation and numerical analysis, it is found that both the 2D and 1D systems give rise to a symmetry-breaking bifurcation (SBB) of the supercritical type. The stability of symmetric and asymmetric states, produced by the SBB, is analyzed through the computation of eigenvalues for perturbation modes and verified by direct simulations. The asymmetric GSs are always stable, while the stability region for vortices shrinks and eventually disappears with the increase of the linear-coupling constant, $\ensuremath{\kappa}$. The SBB in the 2D system does not occur if $\ensuremath{\kappa}$ is too large (at $\ensuremath{\kappa}g{\ensuremath{\kappa}}_{max}$); in that case, the two-component system behaves, essentially, as its single-component counterpart. In the 1D system, both asymmetric and symmetric dipole modes feature an additional oscillatory instability, unrelated to the symmetry breaking. This instability occurs in several regions which expand with the increase of $\ensuremath{\kappa}$.