Formation of spinful dark excitons in Hubbard systems with magnetic superstructures

Abstract

The possibility to form excitons in photoilluminated correlated materials is central from fundamental and application oriented perspectives. In this paper we show how the interplay of electronelectron interactions and a magnetic superstructure leads to the formation of a peculiar spinful dark exciton, which can be detected in ARPES-type experiments and optical measurements. We study this by using matrix product states (MPS) to compute the time evolution of single-particle spectral functions and of the optical conductivity following an electron-hole excitation in a class of one-dimensional correlated band-insulators, simulated by Hubbard models with on-site interactions and alternating local magnetic fields. An excitation in only one specific spin direction leads to an additional band in the gap region of the spectral function only in the spin direction unaffected by the excitation and to an additional peak in the optical conductivity. As both is formed only after the excitation, this is interpreted as a dark exciton, which shows only in one spin direction. Recombination of the excitation happens on much longer time scales than the ones amenable to MPS. We discuss implications for experimental studies in correlated insulator systems.

In-Gap Band Formation in a Periodically Driven Charge Density Wave Insulator

“…. , L} corresponding to a sine transform [61,62] with c k = (2/(L + 1)) −1 k sin(kr i )c i . The OBC momenta differ slightly (∼ 1/(L+1)) from simple fractions of π, e.g.…”

“…Further de-tails on the calculation of the non-equilibrium spectral function with MPS methods can be found in Ref. 62.…”