Ultrafast and anharmonic Rabi oscillations between non-Bloch bands

Abstract

Bloch band theory and bulk-boundary correspondence in non-Hermitian systems are attracting great attention in different areas of science. Interband transitions and Rabi flopping induced by emission or absorption of field quanta are fundamental and well-understood processes in Hermitian systems. However, they are challenged in a non-Hermitian system, where band theory is affected by system boundaries. Here we consider Rabi oscillations in non-Hermitian lattices exhibiting unbalanced non-Hermitian skin effect, and unveil an unprecedented scenario of Rabi flopping. The effective dipole moment of the transitionusually considered a bulk property-is however strongly dependent on boundary conditions. Rabi oscillations become anharmonic and transitions cease to be vertical in the energymomentum plane in systems with open boundaries. Remaining stable even in the presence of complex energies, Rabi oscillations provide a vivid illustration of how competition between non-Hermitian, non-local and Floquet effects can result in significant enhancements of physically measurable quantities.

Designing non-Hermitian real spectra through electrostatics

“…Condensed matter physics has traditionally been studied in the Hermitian context [1], since real energies are necessary for observing stable quantum states. Yet, with intense recent research in non-Hermitian systems, it has become apparent that many of the most exciting contemporary phenomena -exceptional points [2][3][4], non-Hermitian skin localization and modified bulk-boundary correspondence [5][6][7][8], nontrivial spectral topology [9][10][11][12][13], negative entanglement entropy [14,15], effective non-Hermitian curved spaces [16], amplified Rabi frequencies [17] -exist only in the non-Hermitian realm. Fortunately, non-Hermitian systems are not necessarily unstable, since they can still possess real eigenenergies if appropriately designed.…”

Designing non-Hermitian real spectra through electrostatics

“…Condensed matter physics has traditionally been studied in the Hermitian context [1], since real energies are necessary for observing stable quantum states. Yet, with intense recent research in non-Hermitian systems, it has become apparent that many of the most exciting contemporary phenomena -exceptional points [2][3][4], non-Hermitian skin localization and modified bulk-boundary correspondence [5][6][7][8], nontrivial spectral topology [9][10][11][12][13], negative entanglement entropy [14,15], effective non-Hermitian curved spaces [16], amplified Rabi frequencies [17] -exist only in the non-Hermitian realm. Fortunately, non-Hermitian systems are not necessarily unstable, since they can still possess real eigenenergies if appropriately designed.…”

Tidal surface states as fingerprints of non-Hermitian nodal knot metals

“…In those contexts, metallicity refers not to a Fermi surface intersection, but essentially embodies the antithesis of a band insulator, i.e. the absence of spectral gaps 6 Besides parity-time (PT)-symmetric systems with real eigenspectrum due to balanced gain and loss 7 , non-Hermiticity, in combination with topology and surface terminations, has been recently shown to unfold a rich scope of experimentally robust phenomena far beyond mere dissipation [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] (see refs. [27][28][29][30][31] for excellent reviews).…”