Nodal Spectral Functions Stabilized by Non-Hermitian Topology of Quasiparticles

Abstract

In quantum materials, basic observables such as spectral functions and susceptibilities are determined by Green's functions and their complex quasiparticle spectrum rather than by bare electrons. Even in closed many-body systems, this makes a description in terms of effective non-Hermitian (NH) Bloch Hamiltonians natural and intuitive. Here, we discuss how the abundance and stability of nodal phases is drastically affected by NH topology. While previous work has mostly considered complex degeneracies known as exceptional points as the NH counterpart of nodal points, we propose to relax this assumption by only requiring a crossing of the real part of the complex quasiparticle spectra, which entails a band crossing in the spectral function, i.e. a nodal spectral function. Interestingly, such real crossings are topologically protected by the braiding properties of the complex Bloch bands, and thus generically occur already in one-dimensional systems without symmetry or fine-tuning. We propose and study a microscopic lattice model in which a sublattice-dependent interaction stabilizes nodal spectral functions. Besides the gapless spectrum, we identify non-reciprocal charge transport properties after a local potential quench as a key signature of non-trivial band braiding. Finally, in the limit of zero interaction on one of the sublattices, we find a perfectly ballistic unidirectional mode in a non-integrable environment, reminiscent of a chiral edge state known from quantum Hall phases. Our analysis is corroborated by numerical simulations both in the framework of exact diagonalization and within the conserving second Born approximation.

12 pages, 9 figures

References in corpus (22)

• Non-Hermitian Physics
• The physics of exceptional points
• Dirac materials
• Finite-temperature transport in one-dimensional quantum lattice models
• Entanglement Phase Transition Induced by the Non-Hermitian Skin Effect
• Knots and Non-Hermitian Bloch Bands
• Non-Hermitian Edge Burst
• DMFT reveals the non-Hermitian topology in heavy-fermion systems
• Equivalence of the effective non-hermitian Hamiltonians in the context of open quantum systems and strongly-correlated electron systems
• Unusual wave-packet spreading and entanglement dynamics in non-Hermitian disordered many-body systems
• Braid Protected Topological Band Structures with Unpaired Exceptional Points
• Proposal for measuring the finite-temperature Drude weight of integrable systems
• Fourth-Order Exceptional Points in Correlated Quantum Many-Body Systems
• Exceptional points in the one-dimensional Hubbard model
• Topology of multipartite non-Hermitian one-dimensional systems
• A Non-Hermitian Moiré Valley Filter
• Hermitian Topologies originating from non-Hermitian braidings
• Exceptional Non-Hermitian Phases in Disordered Quantum Wires
• Mesoscopic transport signatures of disorder-induced non-Hermitian phases
• Dynamically Induced Exceptional Phases in Quenched Interacting Semimetals
• Surface exceptional points in a topological Kondo insulator
• Landau-Fermi liquids without quasiparticles

Cited by in corpus (1)

• Pseudo-Hermitian Topology of Multiband Non-Hermitian Systems