Other Condensed Matter
- [1] arXiv:2405.14109 (cross-list from cond-mat.mes-hall) [pdf, ps, html, other]
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Title: Effect of boundary roughness on the attenuation of specular phonon reflection in grapheneComments: 17 pages and 10 figuresJournal-ref: Phys. Rev. B 109 (2024) 184207Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Materials Science (cond-mat.mtrl-sci); Other Condensed Matter (cond-mat.other)
The reduced phonon specularity $p$ from boundary roughness scattering plays a major role in the lower thermal conductivity in semiconducting and insulating nanowires and films. Although the well-known Ziman formula $p=\exp(-4\sigma^{2}q_{x}^{2})$, where $\sigma$ and $q_{x}$ denote the root-mean-square boundary roughness and the normal component of the incident phonon wave vector, respectively, and its variants are commonly used in the literature to estimate how roughness attenuates $p$, their validity and accuracy remain poorly understood, especially when the effects of mode conversion cannot be ignored. In this paper, we investigate the accuracy and validity of the more general Ogilvy formula, from which the Ziman formula is derived, by comparing its predictions to the $p$ values computed from Atomistic Green's Function (AGF) simulations for an ensemble of rough boundaries in single-layer graphene. The effects of phonon dispersion, incident angle, polarization, mode conversion, and correlation length are analyzed. Our results suggest that the Ogilvy formula is remarkably accurate for $0<q_{x}<\frac{\pi}{4\sigma}$ when the lateral correlation length $L$ is large or the phonon is at normal incidence. At large $q_{x}$ in the short-wavelength limit, the $q_{x}$-dependence of $p$ becomes significantly weaker. In the large-$L$ limit, the numerical results suggest the existence of a minimum $p$ for short-wavelength phonons, given by $p\sim p_{0}\exp(-\pi^{2}/4)$, where $p_{0}$ is the baseline specularity for the ideal boundary.
- [2] arXiv:2405.14919 (cross-list from nlin.PS) [pdf, ps, html, other]
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Title: Solitons with Self-induced Topological NonreciprocityComments: 6 pages, 3 figuresSubjects: Pattern Formation and Solitons (nlin.PS); Other Condensed Matter (cond-mat.other)
The nonlinear Schrodinger equation can support solitons, self-interacting states that remain sharply localized and behave as nearly independent objects. Here, we demonstrate the existence of solitons with self-induced nonreciprocal dynamics in a discrete version of the nonlinear Schrodinger equation. This nonreciprocal behavior depends on the soliton's power, indicating an interplay between linear and nonlinear terms in the Hamiltonian. Starting from static stable solitons at high power, the nonreciprocal behavior manifests as the power is lowered first by the appearance of nonreciprocal linear instabilities on static solitons and then by a full self-induced nonreciprocal regime, in which the solitons propagate with unidirectional acceleration and amplification. We show this behavior to be topologically protected by winding numbers on the solitons' mean-field Hamiltonian and their linear stability matrix, revealing an intimate connection between nonlinear, nonreciprocal dynamics and point gap topology in non-Hermitian linear Hamiltonians.
- [3] arXiv:2405.14928 (cross-list from cond-mat.quant-gas) [pdf, ps, html, other]
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Title: Unbounded entropy production and violent fragmentation in long-range interacting super-Tonks-Girardeau systemsComments: 14 pages, 13 figuresSubjects: Quantum Gases (cond-mat.quant-gas); Other Condensed Matter (cond-mat.other); Statistical Mechanics (cond-mat.stat-mech); Strongly Correlated Electrons (cond-mat.str-el); Quantum Physics (quant-ph)
We study the non-equilibrium dynamics of a one-dimensional Bose gas with long-range interactions that decay as $(\frac{1}{r^{\alpha}})$ $(0.5 < \alpha <4.0$). We investigate the system when the interactions are suddenly switched from the Tonks-Girardeau (TG) to the super-Tonks-Girardeau (sTG) limit. We find that relaxation is achieved through a complex intermediate dynamics demonstrated by violent fragmentation and chaotic delocalization. We establish that the sTG gas exhibits classical gaseous characteristics and an asymptotic state associated with unbounded entropy production. The phase diagram shows an exponential boundary between the nonthermal (quantum) gas and the thermal (classical) gas. We show the universality of the dynamics by also presenting results for spinless fermions. Weaker quench protocols give a certain degree of control over the relaxation process and induce some intermediate quasi-prethermal states. Our study showcases the complex relaxation behavior of tunable long-range interacting systems that could be engineered in state-of-the-art experiments, e.g. in trapped ions or Rydberg atoms.
- [4] arXiv:2405.15361 (cross-list from quant-ph) [pdf, ps, html, other]
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Title: Multi-qubit quantum state preparation enabled by topology optimizationSubjects: Quantum Physics (quant-ph); Other Condensed Matter (cond-mat.other)
Using topology optimization, we inverse-design nanophotonic cavities enabling the preparation of pure states of pairs and triples of quantum emitters. Our devices involve moderate values of the dielectric constant, operate under continuous laser driving, and yield fidelities to the target (Bell and W) states approaching unity for distant qubits (several natural wavelengths apart). In the fidelity optimization procedure, our algorithm generates entanglement by maximizing the dissipative coupling between the emitters, which allows the formation of multipartite pure steady states in the driven-dissipative dynamics of the system. Our findings open the way towards the efficient and fast preparation of multiqubit quantum states with engineered features, with potential applications for nonclassical light generation, quantum simulation, and quantum sensing.
Cross submissions for Monday, 27 May 2024 (showing 4 of 4 entries )
- [5] arXiv:2401.14339 (replaced) [pdf, ps, html, other]
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Title: Variational Quantum Algorithms for the Allocation of Resources in a Cloud/Edge ArchitectureComments: 14 pages, 13 figuresJournal-ref: IEEE Transactions on Quantum Engineering,2024Subjects: Quantum Physics (quant-ph); Disordered Systems and Neural Networks (cond-mat.dis-nn); Other Condensed Matter (cond-mat.other)
Modern Cloud/Edge architectures need to orchestrate multiple layers of heterogeneous computing nodes, including pervasive sensors/actuators, distributed Edge/Fog nodes, centralized data centers and quantum devices. The optimal assignment and scheduling of computation on the different nodes is a very difficult problem, with NP-hard complexity. In this paper, we explore the possibility of solving this problem with Variational Quantum Algorithms, which can become a viable alternative to classical algorithms in the near future. In particular, we compare the performances, in terms of success probability, of two algorithms, i.e., Quantum Approximate Optimization Algorithm (QAOA) and Variational Quantum Eigensolver (VQE). The simulation experiments, performed for a set of simple problems, %CM230124 that involve a Cloud and two Edge nodes, show that the VQE algorithm ensures better performances when it is equipped with appropriate circuit \textit{ansatzes} that are able to restrict the search space. Moreover, experiments executed on real quantum hardware show that the execution time, when increasing the size of the problem, grows much more slowly than the trend obtained with classical computation, which is known to be exponential.
- [6] arXiv:2403.04332 (replaced) [pdf, ps, other]
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Title: A new metric for the comparison of permittivity models in terahertz time-domain spectroscopyRomain Peretti (IEMN, PHOTONIQUE THZ - IEMN), Mélanie Lavancier (PHOTONIQUE THZ - IEMN, IEMN), Nabil Vindas-Yassine (PHOTONIQUE THZ - IEMN, IEMN), Juliette Vlieghe (PHOTONIQUE THZ - IEMN, IEMN), Theo Hannotte (PHOTONIQUE THZ - IEMN, IEMN), Jean-Francois Lampin (PHOTONIQUE THZ - IEMN, IEMN), François Orieux (L2S)Comments: IEEE Transactions on Terahertz Science and Technology, In pressSubjects: Applied Physics (physics.app-ph); Other Condensed Matter (cond-mat.other); Optics (physics.optics)
We present a robust method, as well as a new metric, for the comparison of permittivity models in terahertz timedomain spectroscopy (THz-TDS). In this work, we perform an extensive noise analysis of a THz-TDS system, we remove and model the unwanted deterministic noises and implement them into our fitting process. This is done using our open-source software, Fit@TDS, available at : this https URL. This work is the first step towards the derivation of uncertainties, and therefore the use of error bars. We hope that this will lead to performing analytical analysis with THz-TDS, as results obtained from different setups will be comparable. Finally, we apply this protocol to the study of a $\alpha$-lactose monohydrate pellet in order to give more insight on the molecular dynamics behind the absorption peaks. The comparison with simulation results is made easier thanks to the probabilities derived from the metric.
- [7] arXiv:2404.00905 (replaced) [pdf, ps, html, other]
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Title: Continuously tunable uniaxial strain control of van der Waals heterostructure devicesZhaoyu Liu, Xuetao Ma, John Cenker, Jiaqi Cai, Zaiyao Fei, Paul Malinowski, Joshua Mutch, Yuzhou Zhao, Kyle Hwangbo, Zhong Lin, Arnab Manna, Jihui Yang, David Cobden, Xiaodong Xu, Matthew Yankowitz, Jiun-Haw ChuComments: 9 pages, 6 figures, to appear in Journal of Applied PhysicsSubjects: Instrumentation and Detectors (physics.ins-det); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Other Condensed Matter (cond-mat.other)
Uniaxial strain has been widely used as a powerful tool for investigating and controlling the properties of quantum materials. However, existing strain techniques have so far mostly been limited to use with bulk crystals. Although recent progress has been made in extending the application of strain to two-dimensional van der Waals (vdW) heterostructures, these techniques have been limited to optical characterization and extremely simple electrical device geometries. Here, we report a piezoelectric-based \textit{in situ} uniaxial strain technique enabling simultaneous electrical transport and optical spectroscopy characterization of dual-gated vdW heterostructure devices. Critically, our technique remains compatible with vdW heterostructure devices of arbitrary complexity fabricated on conventional silicon/silicon dioxide wafer substrates. We demonstrate a large and continuously tunable strain of up to $-0.15\%$ at millikelvin temperatures, with larger strain values also likely achievable. We quantify the strain transmission from the silicon wafer to the vdW heterostructure, and further demonstrate the ability of strain to modify the electronic properties of twisted bilayer graphene. Our technique provides a highly versatile new method for exploring the effect of uniaxial strain on both the electrical and optical properties of vdW heterostructures, and can be easily extended to include additional characterization techniques.