2019/06/13 by E. Perfetto, D. Sangalli, A. Marini +1 · 46 citations
Materials Science · Physics and Astronomy · #Ab initio #Angle-resolved photoemission spectroscopy #Attosecond #Crossover #Excited state #Insulator (electricity) #Josephson effect #Non-equilibrium thermodynamics #Organic and Molecular Conductors Research #Spectral function #Spectroscopy and Quantum Chemical Studies #Strong Light-Matter Interactions #cond-mat.mes-hall #cond-mat.quant-gas
paper · pdf · doi:10.1103/physrevmaterials.3.124601
published in Physical Review Materials 3(12) (American Physical Society) · 13 pages, 9 figures
arxiv created 2019/06/13 · openalex created_date 2019/06/27 · openalex publication_date 2019/12/16 · arxiv updated 2019/12/25 · openalex updated_date 2026/08/06
We consider a ground-state band insulator turning into a nonequilibrium excitonic insulator (NEQ-EI) upon visiting properly selected and physically relevant highly excited states. The NEQ-EI phase, characterized by self-sustained oscillations of the complex order parameter, neatly follows from a nonequilibrium Green's function treatment on the Konstantinov-Perel' contour. We present the first ab initio band structure of LiF, a ground-state bulk insulator, in different NEQ-EI states. We also show that NEQ-EI states can be generated by currently available pump pulses. Peculiar fingerprints of the NEQ-EI phase in time-resolved angle-resolved photoemission spectroscopy spectra are highlighted: (i) during the pump-driving, the system goes through a BEC-BCS crossover and (ii) concomitantly the excitonic spectral structure undergoes a convex-to-concave shape transition; (iii) attosecond pulses shone after the pump-driving at different times tdelay produce a photocurrent that oscillates in tdelay with a pump-tunable frequency---we relate this phenomenon to the ac response of an exotic Josephson junction.