Publications

Order by: publication date number of citations

• Variational truncated Wigner approximation for weakly interacting Bose fields: Dynamics of coupled condensates

  Christopher D. Mink, Axel Pelster, Jens Benary, Herwig Ott, Michael Fleischhauer

  SciPost Phys. 12, 051 (2022) · published 2 February 2022 | Toggle abstract · pdf

  The truncated Wigner approximation is an established approach that describes the dynamics of weakly interacting Bose gases beyond the mean-field level. Although it allows a quantum field to be expressed by a stochastic c-number field, the simulation of the time evolution is still very demanding for most applications. Here, we develop a numerically inexpensive scheme by approximating the c-number field with a variational ansatz. The dynamics of the ansatz function is described by a tractable set of coupled ordinary stochastic differential equations for the respective variational parameters. We investigate the non-equilibrium dynamics of a three-dimensional Bose gas in a one-dimensional optical lattice with a transverse isotropic harmonic confinement. The accuracy and computational inexpensiveness of our method are demonstrated by comparing its predictions to experimental data.

  7 citations

• Traveling-wave antenna model for terahertz radiation from laser-plasma interactions

  Jiayu Zhao, Qining Wang, Yuchen Hui, Yamin Chen, Feifan Zhu, Zuanming Jin, Alexander P. Shkurinov, Yan Peng, Yiming Zhu, Songlin Zhuang, Li Lao

  SciPost Phys. Core 5, 046 (2022) · published 29 September 2022 | Toggle abstract · pdf

  Generation of terahertz (THz) wave from air plasma induced by femtosecond laser pulses with a single central frequency (the so-called “single-color”) is one of the fundamental interactions between light and matter, and is also the basis of subsequent pumping schemes using two- or multi-color laser fields. Recently, more states of media beyond gas (e.g., atomic cluster and liquid) via photo-ionization have brought new experimental observations of THz radiation, which can no longer be simply attributed to the mainstream model of the transition-Cherenkov radiation (TCR), thus making the whole picture unclear. Here, we revisited the mechanism of this dynamic process in a new view of the traveling-wave antenna (TWA) model. By successfully reproducing the reported far-field THz radiation profiles from various plasma filament arrangements, the wide applicability of the TWA theory has been revealed. On the other hand in the microscopic view, we investigated the plasma oscillation during filamentation aiming at further bridging the plasma filament and the antenna. Accordingly, THz-plasma resonance has been theoretically and experimentally demonstrated as the elementary THz emitter, paving the way towards fully understanding this important single-color plasma based THz source.

  7 citations

• Extracting electronic many-body correlations from local measurements with artificial neural networks

  Faluke Aikebaier, Teemu Ojanen, Jose L. Lado

  SciPost Phys. Core 6, 030 (2023) · published 17 April 2023 | Toggle abstract · pdf

  The characterization of many-body correlations provides a powerful tool for analyzing correlated quantum materials. However, experimental extraction of quantum entanglement in correlated electronic systems remains an open problem in practice. In particular, the correlation entropy quantifies the strength of quantum correlations in interacting electronic systems, yet it requires measuring all the single-particle correlators of a macroscopic sample. To circumvent this bottleneck, we introduce a strategy to obtain the correlation entropy of electronic systems solely from a set of local measurements. We show that, by combining local particle-particle and density-density correlations with a neural-network algorithm, the correlation entropy can be predicted accurately. Specifically, we show that for a generalized interacting fermionic model, our algorithm yields an accurate prediction of the correlation entropy from a set of noisy local correlators. Our work shows that the correlation entropy in interacting electron systems can be reconstructed from local measurements, providing a starting point to experimentally extract many-body correlations with local probes.

  7 citations

• Marginal deformations from type IIA supergravity

  Nikolay Bobev, Pieter Bomans, Fridrik Freyr Gautason, Vincent S. Min

  SciPost Phys. 10, 140 (2021) · published 10 June 2021 | Toggle abstract · pdf

  We study marginal deformations of a class of three-dimensional $\mathcal{N}=2$ SCFTs that admit a holographic dual description in massive type IIA supergravity. We compute the dimension of the conformal manifold in these SCFTs and identify a special submanifold with enhanced flavor symmetry. We show how to apply the TsT transformation of Lunin-Maldacena to construct explicit supersymmetric AdS$_4$ solutions of massive type IIA supergravity with non-trivial internal fluxes that are the holographic dual of these marginal deformations. Finally, we also briefly comment on a class of RG flows between some of these SCFTs that also admit a holographic realization.

  7 citations

• Anisotropy-mediated reentrant localization

  Xiaolong Deng, Alexander L. Burin, Ivan M. Khaymovich

  SciPost Phys. 13, 116 (2022) · published 24 November 2022 | Toggle abstract · pdf

  We consider a 2d dipolar system, $d=2$, with the generalized dipole-dipole interaction $\sim r^{-a}$, and the power $a$ controlled experimentally in trapped-ion or Rydberg-atom systems via their interaction with cavity modes. We focus on the dilute dipolar excitation case when the problem can be effectively considered as single-particle with the interaction providing long-range dipolar-like hopping. We show that the spatially homogeneous tilt $\beta$ of the dipoles giving rise to the anisotropic dipole exchange leads to the non-trivial reentrant localization beyond the locator expansion, $a<d$, unlike the models with random dipole orientation. The Anderson transitions are found to occur at the finite values of the tilt parameter $\beta = a$, $0<a<d$, and $\beta = a/(a-d/2)$, $d/2<a<d$, showing the robustness of the localization at small and large anisotropy values. Both exact analytical methods and extensive numerical calculations show power-law localized eigenstates in the bulk of the spectrum, obeying recently discovered duality $a\leftrightarrow 2d-a$ of their spatial decay rate, on the localized side of the transition, $a>a_{AT}$. This localization emerges due to the presence of the ergodic extended states at either spectral edge, which constitute a zero fraction of states in the thermodynamic limit, decaying though extremely slowly with the system size.

  7 citations

• Pairing instabilities of the Yukawa-SYK models with controlled fermion incoherence

  Wonjune Choi, Omid Tavakol, Yong Baek Kim

  SciPost Phys. 12, 151 (2022) · published 9 May 2022 | Toggle abstract · pdf

  The interplay of non-Fermi liquid and superconductivity born out of strong dynamical interactions is at the heart of the physics of unconventional superconductivity. As a solvable platform of the strongly correlated superconductors, we study the pairing instabilities of the Yukawa-Sachdev-Ye-Kitaev (Yukawa-SYK) model, which describes spin-1/2 fermions coupled to bosons by the random, all-to-all, spin-independent and dependent Yukawa interactions. In contrast to the previously studied models, the random Yukawa couplings are sampled from a collection of Gaussian ensembles whose variances follow a continuous distribution rather than being fixed to a constant. By tuning the analytic behaviour of the distribution, we could control the fermion incoherence to systematically examine various normal states ranging from the Fermi liquid to non-Fermi liquids that are different from the conformal solution of the SYK model with a constant variance. Using the linearised Eliashberg theory, we show that the onset of the unconventional spin-triplet pairing is preferred with the spin-dependent interactions while all pairing channels show instabilities with the spin-independent interactions. Although the interactions shorten the lifetime of the fermions in the non-Fermi liquid, the same interactions also dress the bosons to strengthen the tendency to pair the incoherent fermions. As a consequence, the onset temperature $T_c$ of the pairing is enhanced in the non-Fermi liquid compared to the case of the Fermi liquid.

  7 citations

• High Efficiency Configuration Space Sampling -- probing the distribution of available states

  Paweł T. Jochym, Jan Łażewski

  SciPost Phys. 10, 129 (2021) · published 3 June 2021 | Toggle abstract · pdf

  Substantial acceleration of research and more efficient utilization of resources can be achieved in modelling investigated phenomena by identifying the limits of system's accessible states instead of tracing the trajectory of its evolution. The proposed strategy uses the Metropolis-Hastings Monte-Carlo sampling of the configuration space probability distribution coupled with physically-motivated prior probability distribution. We demonstrate this general idea by presenting a high performance method of generating configurations for lattice dynamics and other computational solid state physics calculations corresponding to non-zero temperatures. In contrast to the methods based on molecular dynamics, where only a small fraction of obtained data is used, the proposed scheme is distinguished by a considerably higher, reaching even 80%, acceptance ratio and much lower amount of computation required to obtain adequate sampling of the system in thermal equilibrium at non-zero temperature.

  7 citations

• Mobility control as state-making in civil war: Forcing exit, selective return and strategic laissez-faire

  Christiane Fröhlich, Lea Müller-Funk

  Mig. Pol. 2, 001 (2023) · published 27 March 2023 | Toggle abstract · pdf

  This paper addresses the question of how different actors attempt to control mobility during civil war, and how mobility control and processes of state-making interact in such settings. Mobility in civil wars is often considered a political act by the various actors involved: Leaving the country can be perceived as an act of opposition, as can moving between territories which are controlled by different, opposing factions. Drawing on literature on strategic displacement and migration politics and combining this with empirical insights from the ongoing wars in Libya and Syria, the paper identifies three mechanisms of mobility control in civil war settings: forcing exit, selective return as a form of expulsion, and strategic laissez-faire as the intentional absence of regulation regarding displacement and return. The analysis reveals that all three mechanisms are employed by state actor(s), rebels, and militias, and can be understood as elements of a new (post)war order that includes some citizens while excluding others depending on perceptions of political threats. We interpret the three mechanisms as ways in which actors in civil war settings attempt to manipulate a country’s demography in their own favour in a process of state-making. The paper is based on fieldwork conducted between 2018 and 2021 in Syria, Lebanon, Libya, and Tunisia.

  7 citations

• Non-supersymmetric AdS from string theory

  Zihni Kaan Baykara, Daniel Robbins, Savdeep Sethi

  SciPost Phys. 15, 224 (2023) · published 4 December 2023 | Toggle abstract · pdf

  We construct non-supersymmetric $AdS_3$ solutions of the $\mathrm O(16)× \mathrm O(16)$ heterotic string. Most of the backgrounds have a classical worldsheet definition but are quantum string vacua in the sense that string loop corrections change the curvature of spacetime. At one-loop, the change in the cosmological constant is positive but never sufficient to uplift to de Sitter space. By computing the spectrum of spacetime scalars, we show that there are no tachyons below the BF bound. We also show that there is a solution with no spacetime NS-NS flux. This background has no classical string limit. Surprisingly, there appears to be parametric control over these constructions, which provide a framework for exploring quantum gravity and holography without supersymmetry.

  7 citations

• Interacting edge states of fermionic symmetry-protected topological phases in two dimensions

  Joseph Sullivan, Meng Cheng

  SciPost Phys. 9, 016 (2020) · published 5 August 2020 | Toggle abstract · pdf

  Recently, it has been found that there exist symmetry-protected topological phases of fermions, which have no realizations in non-interacting fermionic systems or bosonic models. We study the edge states of such an intrinsically interacting fermionic SPT phase in two spatial dimensions, protected by $\mathbb{Z}_4\times\mathbb{Z}_2^T$ symmetry. We model the edge Hilbert space by replacing the internal $\mathbb{Z}_4$ symmetry with a spatial translation symmetry, and design an exactly solvable Hamiltonian for the edge model. We show that at low-energy the edge can be described by a two-component Luttinger liquid, with nontrivial symmetry transformations that can only be realized in strongly interacting systems. We further demonstrate the symmetry-protected gaplessness under various perturbations, and the bulk-edge correspondence in the theory.

  7 citations