Arxiv Selection Aug 2019

Aug 1-Aug 7 Zehan Li, Aug 8- Aug 14 Jiansong Pan, Aug 15- Aug 21 Ahmet Keles, Aug 22 - Aug 28 Haiping Hu

Aug 1

arXiv:1907.12566 (cross-list from cond-mat.mes-hall) [pdf, other]

Observation of non-Hermitian bulk-boundary correspondence in quantum dynamics

Lei Xiao, Tianshu Deng, Kunkun Wang, Gaoyan Zhu, Zhong Wang, Wei Yi, Peng Xue

Comments: 15 pages, 9 figures

Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Quantum Gases (cond-mat.quant-gas); Strongly Correlated Electrons (cond-mat.str-el); Optics (physics.optics); Quantum Physics (quant-ph)

Bulk-boundary correspondence, a central principle in topological matter relating bulk topological invariants to edge states, breaks down in a generic class of nonHermitian systems that have so far eluded experimental effort. Here we theoretically predict and experimentally observe non-Hermitian bulk-boundary correspondence, a fundamental generalization of the conventional bulk-boundary correspondence, in discrete-time non-unitary quantum-walk dynamics of single photons. We experimentally demonstrate photon localizations near boundaries even in the absence of topological edge states, thus confirming the non-Hermitian skin effect. Facilitated by our experimental scheme of edge-state reconstruction, we directly measure topological edge states, which match excellently with non-Bloch topological invariants calculated from localized bulk-state wave functions. Our work unequivocally establishes the non-Hermitian bulk-boundary correspondence as a general principle underlying non-Hermitian topological systems, and paves the way for a complete understanding of topological matter in open systems.

Aug 2

arXiv:1908.00108 [pdf, other]

Strongly correlated quantum droplets in quasi-1D dipolar Bose gas

Rafał Ołdziejewski, Wojciech Górecki, Krzysztof Pawłowski, Kazimierz Rzążewski

Comments: 9 pages, 4 figures, comments welcome

Subjects: Quantum Gases (cond-mat.quant-gas); Quantum Physics (quant-ph)

We exploit a few- to many-body approach to study strongly interacting dipolar bosons in the quasi-one-dimensional system. The dipoles attract each other while the short range interactions are repulsive. Solving numerically exactly the multi-atom Schrödinger equation, we discover that such systems can exhibit not only the well known bright soliton solutions but also novel quantum droplets for a strongly coupled case. For larger systems, basing on microscopic properties of the found few-body solution, we propose a new generalization of the Gross-Pitaevskii equation (GPE) that incorporates the Lieb-Liniger energy in a local density approximation. Not only does such a framework provide an alternative mechanism of the droplet stability, but it also introduces means to further analyze this previously unexplored quantum phase. In the limiting strong repulsion case, yet another simple multi-atom model is proposed. We stress that the celebrated Lee-Huang-Yang term in the GPE is not applicable in this case.

Aug 5

arXiv:1908.00761 [pdf, other]

Observation of Quantum Droplets in a Heteronuclear Bosonic Mixture

C. D'Errico, A. Burchianti, M. Prevedelli, L. Salasnich, F. Ancilotto, M. Modugno, F. Minardi, C. Fort

Comments: 9 pages, 7 figures

Subjects: Quantum Gases (cond-mat.quant-gas)

We show that the Lee-Huang-Yang (LHY) energy functional for a heteronuclear Bose mixture can be accurately approximated by an expression that has the same functional form as in the homonuclear case. It is characterized by two exponents, which can be treated as fitting parameters. We demonstrate that the values of these parameters which preserve the invariance under permutation of the two atomic species are exactly those of the homonuclear case. Deviations from the actual expression of LHY energy functional are discussed quantitatively.