Possible hidden phases in photo-doped Mott insulators

Y. Murakami1

1Center for Emergent Matter Science, RIKEN, Wako, Saitama 351-0198, Japan

Doping charge carriers into Mott insulators provides a pathway to produce intriguing emergent phenomena. In equilibrium systems, doping can be chemically controlled. On the other hand, photo-doping, where particles are excited across the Mott gap, provides an alternative way. Compared to chemical-doping, photo-doping creates a wider variety of charge carriers, which may lead to the emergence of fascinating nonequilibrium states. In particular, when the gap is large, the lifetime of photo-carriers is exponentially enhanced, leading to quasi-steady states after intraband cooling of photo-carriers.

In this talk, we explore possible hidden phases that arise as quasi-steady states of photodoped Mott insulators using the quasi-equilibrium approach [1]. Within this approach, we treat the photo-doped state as an equilibrium state of an effective model for a given photo-doping level. We apply the idea to the 1D extended Hubbard model. In the first part [1], we present our numerical results obtained with the infinite time-evolving block decimation. We show the emergence of the so-called η-pairing phase and the string charge-density-wave phase, and discuss their physical properties. In the second part [2], we reveal the analytical aspects of these photo-doped states. We show that the corresponding wave function in the large on-site interaction limit can be expressed as , which indicates the separation of spin, charge and η−spin degrees of freedoms. Here η−spin represents the type of the photo-carriers, i.e. doublons and holons. This state is analogous to the celebrated Ogata-Shiba state of the doped Hubbard model in equilibrium. The expression provides us useful insight into the properties of the photo-doped states. Our results demonstrate that the emergent degrees of freedom activated by photo-doping can lead to peculiar types of quantum states absent in equilibrium.

1. Y. Murakami, S. Takayoshi, T. Kaneko, Z. Sun, D. Golež, A. J. Millis, P. Werner, Comm. Phys. 5, 23 (2022)
2. Y. Murakami, S. Takayoshi, T. Kaneko, A. Läuchli, P. Werner, Phys. Rev. Lett. 130, 106501 (2023)