collective mode
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2022 ◽  
Vol 7 (1) ◽  
Author(s):  
Romain Grasset ◽  
Kota Katsumi ◽  
Pierre Massat ◽  
Hai-Hu Wen ◽  
Xian-Hui Chen ◽  
...  

AbstractWe investigate the collective mode response of the iron-based superconductor Ba1−xKxFe2As2 using intense terahertz (THz) light. In the superconducting state a THz Kerr signal is observed and assigned to nonlinear THz coupling to superconducting degrees of freedom. The polarization dependence of the THz Kerr signal is remarkably sensitive to the coexistence of a nematic order. In the absence of nematic order the C4 symmetric polarization dependence of the THz Kerr signal is consistent with a coupling to the Higgs amplitude mode of the superconducting condensate. In the coexisting nematic and superconducting state the signal becomes purely nematic with a vanishing C4 symmetric component, signaling the emergence of a superconducting collective mode activated by nematicity.


2022 ◽  
Vol 2022 (1) ◽  
Author(s):  
Mike Blake ◽  
Richard A. Davison

Abstract We study the connection between many-body quantum chaos and energy dynamics for the holographic theory dual to the Kerr-AdS black hole. In particular, we determine a partial differential equation governing the angular profile of gravitational shock waves that are relevant for the computation of out-of-time ordered correlation functions (OTOCs). Further we show that this shock wave profile is directly related to the behaviour of energy fluctuations in the boundary theory. In particular, we demonstrate using the Teukolsky formalism that at complex frequency ω∗ = i2πT there exists an extra ingoing solution to the linearised Einstein equations whenever the angular profile of metric perturbations near the horizon satisfies this shock wave equation. As a result, for metric perturbations with such temporal and angular profiles we find that the energy density response of the boundary theory exhibit the signatures of “pole-skipping” — namely, it is undefined, but exhibits a collective mode upon a parametrically small deformation of the profile. Additionally, we provide an explicit computation of the OTOC in the equatorial plane for slowly rotating large black holes, and show that its form can be used to obtain constraints on the dispersion relations of collective modes in the dual CFT.


Author(s):  
Wieland Schöllkopf

This Highlight showcases the Research Paper entitled Collective-Mode Enhanced Matter-Wave Optics (Phys. Rev. Lett. 127, 100401 (2021), DOI: 10.1103/Phys- RevLett.127.100401).


2021 ◽  
Vol 11 (4) ◽  
Author(s):  
Pavel E. Dolgirev ◽  
Yi-Fan Qu ◽  
Mikhail B. Zvonarev ◽  
Tao Shi ◽  
Eugene Demler

2021 ◽  
Vol 127 (10) ◽  
Author(s):  
Christian Deppner ◽  
Waldemar Herr ◽  
Merle Cornelius ◽  
Peter Stromberger ◽  
Tammo Sternke ◽  
...  

2020 ◽  
Vol 102 (13) ◽  
Author(s):  
Koujiro Hoshi ◽  
Jun-ichiro Kishine ◽  
Jun-ichiro Ohe

2020 ◽  
Vol 34 (31) ◽  
pp. 2030001
Author(s):  
Hiroyasu Koizumi ◽  
Alto Ishikawa

According to the standard theory of superconductivity, the origin of superconductivity is electron pairing. The induced current by a magnetic field is calculated by the linear response to the vector potential, and the supercurrent is identified as the dissipationless flow of the paired electrons, while single electrons flow with dissipation. This supercurrent description suffers from the following serious problems: (1) it contradicts the reversible superconducting-normal phase transition in a magnetic field observed in type I superconductors; (2) the gauge invariance of the supercurrent induced by a magnetic field requires the breakdown of the global [Formula: see text] gauge invariance, or the nonconservation of the particle number; and (3) the explanation of the ac Josephson effect is based on the boundary condition that is different from the real experimental one. We will show that above problems are resolved if the supercurrent is attributed to the collective mode arising from the Berry connection for many-body wavefunctions. Problem (1) is resolved by attributing the appearance and disappearance of the supercurrent to the abrupt appearance and disappearance of topologically protected loop currents produced by the Berry connection; problem (2) is resolved by assigning the non-conserved number to that for the particle number participating in the collective mode produced by the Berry connection; and problem (3) is resolved by identifying the relevant phase in the Josephson effect is that arising from the Berry connection, and using the modified Bogoliubov transformation that conserves the particle number. We argue that the required Berry connection arises from spin-twisting itinerant motion of electrons. For this motion to happen, the Rashba spin–orbit interaction has to be added to the Hamiltonian for superconducting systems. The collective mode from the Berry connections is stabilized by the pairing interaction that changes the number of particles participating in it; thus, the superconducting transition temperatures for some superconductors is given by the pairing energy gap formation temperature as explained in the BCS theory. The topologically protected loop currents in this case are generated as cyclotron motion of electrons that is quantized by the Berry connection even without an external magnetic field. We also explain a way to obtain the Berry connection from spin-twisting itinerant motion of electrons for a two-dimensional model where the on-site Coulomb repulsion is large and doped holes form small polarons. In this model, the electron pairing is not required for the stabilization of the collective mode, and the supercurrent is given as topologically protected spin-vortex-induced loop currents (SVILCs).


Nanomaterials ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1952
Author(s):  
Pablo de la Hoz ◽  
Anton Sakovich ◽  
Alexander Mikhalychev ◽  
Matthew Thornton ◽  
Natalia Korolkova ◽  
...  

We present a theoretical proposal for an integrated four-wave mixing source of narrow-band path-entangled photon pairs with efficient spatial pump self-rejection. The scheme is based on correlated loss in a system of waveguides in Kerr nonlinear media. We calculate that this setup gives the possibility for upwards of 100 dB pump rejection, without additional filtering. The effect is reached by driving the symmetric collective mode that is strongly attenuated by an engineered dissipation, while photon pairs are born in the antisymmetric mode. A similar set-up can additionally be realized for the generation of two-photon NOON states, also with pump self-rejection. We discuss the implementation of the scheme by means of the coherent diffusive photonics, and demostrate its feasibility in both glass (such as fused silica-glass and IG2) and planar semiconductor waveguide structures in indium phosphide (InP) and in silicon.


2020 ◽  
Vol 9 (1) ◽  
pp. 374-395
Author(s):  
Rafael Ignacio Estrada Mejia ◽  
Carla Guerrón Guerron Montero

This article aims to decrease the cultural invisibility of the wealthy by exploring the Brazilian emergent elites and their preferred living arrangement: elitist closed condominiums (BECCs) from a micropolitical perspective.  We answer the question: What is the relationship between intimacy and subjectivity that is produced in the collective mode of existence of BECCs? To do so, we trace the history of the elite home, from the master’s house (casa grande) to contemporary closed condominiums. Following, we discuss the features of closed condominiums as spaces of segregation, fragmentation and social distinction, characterized by minimal public life and an internalized sociability. Finally, based on ethnographic research conducted in the mid-size city of Londrina (state of Paraná) between 2015 and 2017, we concentrate on four members of the emergent elite who live in BECCs, addressing their collective production of subjectivity. 


2020 ◽  
Vol 23 (06) ◽  
pp. 2050019
Author(s):  
VALERY TERESHKO

We consider a honeybee colony as a dynamical system gathering information from an environment and accordingly adjusting its behavior. Collective foraging behavior is shown to be triggered by the change of either colony size or profitability of exploited nectar sources. The collective mode provides greater productivity compared to the individual one. The latter does not diminish the importance of individual behavior that ensures the adaptivity of the system. Thus, the transition from the phase of individual behavior to a more complex phase, combining both individual and collective modes, provides the most effective scenario of honeybee colony foraging.


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