Engineering non-Hermitian skin effect with band topology in ultracold gases

Zhou, Lihong; Li, Haowei; Wu, Yi; Cui, Xiaoling

doi:10.1038/s42005-022-01021-y

Cited by 28 publications

(7 citation statements)

References 66 publications

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“…There exist several physical incarnations that can be used to explore the non-Hermitian systems [48][49][50][51][52][53][54][55][56][57][58][59][60][61][62] , including the cold atoms [48][49][50][51] , electrical circuits [52][53][54][55][56][57] , photonic and acoustic systems [58][59][60][61][62] . Among them, electric circuits have been widely used because the circuit structure can be flexibly designed to facilitate integration and mass production.…”

Section: Experimental Implementationmentioning

confidence: 99%

Anomalous non-Hermitian skin effect: the topological inequivalence of skin modes versus point gap

Guo¹,

Bao²,

Zhu³

et al. 2023

Preprint

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Non-Hermitian skin effect, the localization of an extensive number of open boundary eigenstates at the boundaries of the system, has greatly expanded the frontier of physical laws. It has long been believed that the present of skin modes is equivalent to the topologically nontrivial point gap. However, we find that this concomitance can be broken, i.e., the skin modes can be present or absent whereas the point gap is topologically trivial or nontrivial, respectively, named anomalous non-Hermitian skin effect. This anomalous phenomenon arises whenever the unidirectional hopping amplitudes among subsystems are emergence, in which sub-chains have the decoupling-like behaviors and only contribute to the energy levels while without particle occupation. The occurrence of the anomalous non-Hermitian skin effect is accompanied by the mutations of the open boundary eigenvalues, whose structure exhibits the multifold exceptional point and can not be recovered by continuum bands. Moreover, an experimental setup using circuits is proposed to simulate this novel effect. Our results reveal the topologically inequivalent between skin modes and point gap. This new effect not only can give a deeper understanding of non-Bloch theory and the critical phenomenon in non-Hermitian systems, but may also inspire new applications such as in the sensors field.

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Section: Experimental Implementationmentioning

confidence: 99%

Anomalous non-Hermitian skin effect: the topological inequivalence of skin modes versus point gap

Guo¹,

Bao²,

Zhu³

et al. 2023

Preprint

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show abstract

“…While the excellent tunability of Raman lattices provides access to a plethora of dynamic topological phenomena either in quench processes or periodically-driven Floquet settings [8][9][10], a largely unexplored possibility is the further introduction of dissipation. A dissipative Raman lattice should exhibit even more exotic properties in the highly non-trivial context of quantum open systems [11]. This is expected, since dissipation has been shown to stabilize interesting manybody phases [12][13][14] or phase transitions [15][16][17][18][19] under the framework of quantum master equation.…”

Section: Introductionmentioning

confidence: 99%

Dissipative two-dimensional Raman lattice

Li¹,

Yi²

2022

Preprint

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We show that a dissipative two-dimensional Raman lattice can be engineered in a two-component ultracold atomic gas, where the interplay of the two-dimensional spin-orbit coupling and lightinduced atom loss gives rise to a density flow diagonal to the underlying square lattice. The flow is driven by the non-Hermitian corner skin effect, under which eigenstates localize toward one corner of the system. We illustrate that the topological edge states of the system can only be accounted for by the non-Bloch band theory where the deformation of the bulk eigenstates are explicitly considered. The directional flow can be detected through the dynamic evolution of an initially localized condensate in the lattice, or by introducing an immobile impurity species that interact spin-selectively with a condensate in the ground state of the Raman lattice.

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“…Non-Hermitian parity-time (PT ) symmetry physics has experienced rapid developments in the last two decades, especially in the field of optics, where the balanced optical gain and loss can be modeled by a PT -symmetric Hamiltonian, and it is found that gain and loss can serve as new engineering tools and also lead to abundant new and unexpected features [34][35][36][37][38]. These great developments inspired the interest in extending cold atom physics from Hermitian to non-Hermitian regime, with the prospect of exploring unidirectional transportation [39], non-Hermitian skin effect [40][41][42][43], soliton [44][45][46], double-well [47][48][49] and Hubbard model [50,51] in open environments, etc. In cold atom systems, controlled atomic loss can be realized by extracting atoms from the atomic gas via atom-light interaction [52]; while the atomic gain is proposed to be realized by injecting atoms into the atomic gas using an atom laser [53].…”

Section: Introductionmentioning

confidence: 99%

Phonon and maxon instability in Bose–Einstein condensates with parity-time symmetric spin–orbit coupling

Qin,

Zhou,

Dong

2023

New J. Phys.

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Parity-time ( P T ) symmetry has drawn great research interest in non-Hermitian physics. Recently, there is an emerging model of P T -symmetric spin–orbit coupling (SOC) which could be realized with spin-1/2 atomic Bose–Einstein condensates (BECs) when the two spin components are respectively subjected to momentum-dependent gain and loss (Qin et al 2022 New J. Phys. 24 063025). In this model, inter-atom interaction has no influence on the P T -symmetric plane waves. Thus, collective excitation playing the role of fingerprint of inter-atom interaction is investigated in this paper. For the phonon excitation, it is shown that the repulsive interaction between atoms in different spin states, which tends to drive the atoms to populate in only one spin component, can break the P T -symmetry, and leads to a phonon instability. Whereas, for the case of the phonon-maxon-roton collective excitation spectrum, the repulsive interaction between atoms in different spin states can lead to a maxon instability, which does not occur in Hermitian BEC systems (dipolar BECs or BECs with Raman induced SOC). Simulation of the time evolution of the plane wave solution against small noise shows that the maxon instability can result in the formation of a supersolid-like stripe pattern at the initial stage, but the non-Hermitian nature of the system finally destroys the pattern. The phase diagram of stability shows that the Rabi coupling and repulsive interaction between the atoms in the same spin state can stabilize the system.

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Engineering non-Hermitian skin effect with band topology in ultracold gases

Cited by 28 publications

References 66 publications

Anomalous non-Hermitian skin effect: the topological inequivalence of skin modes versus point gap

Anomalous non-Hermitian skin effect: the topological inequivalence of skin modes versus point gap

Dissipative two-dimensional Raman lattice

Phonon and maxon instability in Bose–Einstein condensates with parity-time symmetric spin–orbit coupling

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