collective modes
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2022 ◽  
Vol 105 (2) ◽  
Author(s):  
Alexander V. Balatsky ◽  
Benjo Fraser ◽  
Henrik S. Røising
Keyword(s):  

2021 ◽  
Vol 104 (6) ◽  
Author(s):  
Margaret E. Carrington ◽  
Bailey M. Forster ◽  
Sofiya Makar

2021 ◽  
Vol 104 (24) ◽  
Author(s):  
SK Firoz Islam ◽  
Alexander A. Zyuzin
Keyword(s):  

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Jian-Song Pan ◽  
Wei Yi ◽  
Jiangbin Gong

AbstractThe spontaneous breaking of parity-time ($${{{{{{{\mathcal{PT}}}}}}}}$$ PT ) symmetry yields rich critical behavior in non-Hermitian systems, and has stimulated much interest, albeit most previous studies were performed within the single-particle or mean-field framework. Here, by studying the collective excitations of a Fermi superfluid with $${{{{{{{\mathcal{PT}}}}}}}}$$ PT -symmetric spin-orbit coupling, we uncover an emergent $${{{{{{{\mathcal{PT}}}}}}}}$$ PT -symmetry breaking in the Anderson-Bogoliubov (AB) collective modes, even as the superfluid ground state retains an unbroken $${{{{{{{\mathcal{PT}}}}}}}}$$ PT symmetry. The critical point of the transition is marked by a non-analytic kink in the speed of sound, which derives from the coalescence and annihilation of the AB mode and its hole partner, reminiscent of the particle-antiparticle annihilation. The system consequently becomes immune to low-frequency external perturbations at the critical point, a phenomenon associated with the spectral topology of the complex quasiparticle dispersion. This critical phenomenon offers a fascinating route toward perturbation-free quantum states.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Eva Arianna Aurelia Pogna ◽  
Leonardo Viti ◽  
Antonio Politano ◽  
Massimo Brambilla ◽  
Gaetano Scamarcio ◽  
...  

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Daichi Kurebayashi ◽  
Naoto Nagaosa

AbstractEmergent electromagnetism in magnets originates from the strong coupling between conduction electron spins and those of noncollinear ordered moments and the consequent Berry phase. This offers possibilities to develop new functions of quantum transport and optical responses. The emergent inductance in spiral magnets is an example recently proposed and experimentally demonstrated, using the emergent electric field induced by alternating currents. However, the microscopic theory of this phenomenon is missing, which should reveal factors to determine the magnitude, sign, frequency dependence, and nonlinearity of the inductance L. Here we theoretically study electromagnetic responses of spiral magnets by taking into account their collective modes. In sharp contrast to collinear spin-density wave, the system remains metallic even in one dimension, and the canonical conjugate relation of uniform magnetization and phason coordinate plays an essential role, determining the properties of L. This result opens a way to design the emergent inductance of desired properties.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Eva Arianna Aurelia Pogna ◽  
Leonardo Viti ◽  
Antonio Politano ◽  
Massimo Brambilla ◽  
Gaetano Scamarcio ◽  
...  

AbstractNear-field microscopy discloses a peculiar potential to explore novel quantum state of matter at the nanoscale, providing an intriguing playground to investigate, locally, carrier dynamics or propagation of photoexcited modes as plasmons, phonons, plasmon-polaritons or phonon-polaritons. Here, we exploit a combination of hyperspectral time domain spectroscopy nano-imaging and detectorless scattering near-field optical microscopy, at multiple terahertz frequencies, to explore the rich physics of layered topological insulators as Bi2Se3 and Bi2Te2.2Se0.8, hyperbolic materials with topologically protected surface states. By mapping the near-field scattering signal from a set of thin flakes of Bi2Se3 and Bi2Te2.2Se0.8 of various thicknesses, we shed light on the nature of the collective modes dominating their optical response in the 2-3 THz range. We capture snapshots of the activation of transverse and longitudinal optical phonons and reveal the propagation of sub-diffractional hyperbolic phonon-polariton modes influenced by the Dirac plasmons arising from the topological surface states and of bulk plasmons, prospecting new research directions in plasmonics, tailored nanophotonics, spintronics and quantum technologies.


2021 ◽  
Vol 2094 (2) ◽  
pp. 022012
Author(s):  
V E Zakhvataev ◽  
O S Volodko ◽  
L A Kompaniets ◽  
D V Zlobin

Abstract Terahertz density fluctuations in DNA have been recognized to be associated with biological function of DNA and widely studied both experimentally and theoretically. In the present work, we investigate numerically a new model for the terahertz dynamics of density fluctuations in DNA, proposed earlier. This model considers the length scales corresponding to wave numbers up to the position of the maximum of the static structure factor and allows to reflect structural effects caused by the dependence of the static structure factor on wave number. We study the parametric dependencies of the model to elucidate the effect of dlocalization of the dynamics of density fluctuations caused by structural effects.


2021 ◽  
Vol 2021 (11) ◽  
pp. 041
Author(s):  
Michael Dine ◽  
Nicolas Fernandez ◽  
Akshay Ghalsasi ◽  
Hiren H. Patel

Abstract Axions have for some time been considered a plausible candidate for dark matter. They can be produced through misalignment, but it has been argued that when inflation occurs before a Peccei-Quinn transition, appreciable production can result from cosmic strings. This has been the subject of extensive simulations. But there are reasons to be skeptical about the possible role of axion strings. We review and elaborate on these questions, and argue that parametrically strings are already accounted for by the assumption of random misalignment angles. We review and elaborate on these questions, and provide several qualitative arguments that parametrically strings are already accounted for by the assumption of random misalignment angles. The arguments are base on considerations of the collective modes of the string solutions, on computations of axion radiation in particular models, and reviews of simulations.


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