Quantum Gas Microscopy of an XY model in Shaken Triangular Lattices

Frustrated spin systems are one of the most intriguing problems of magnetism and condensed matter physics. Even in the case of the simplest geometrical spin frustration that occurs in the triangular structure with antiferromagnetic interactions, competition between the interactions and the lattice geometry can bring about rich spin configurations. There has recently been steady progress in simulating quantum magnetism using a quantum gas microscope (QGM). In our group, we have developed an experimental setup of an ⁸⁷Rb Bose gas in an optical triangular lattice with QGM, which can reveal real-space properties in the frustrated spin system. To introduce the antiferromagnetic interactions, we use a lattice shaking technique, which enables independent control of the time-averaged effective tunneling by sinusoidally modulating the position of the entire lattice. Mapping the BEC phase onto spins allows the simulation of the XY model. We identify the interference patterns of each phase in the model by the time-of-flight method. A geometrical frustration induced by negative tunneling leads to two-fold ground states corresponding to two chiral modes. Due to spontaneous symmetry breaking, one of the chiral modes randomly appears sequence by sequence. Furthermore, simultaneous occupation of the two chiral modes is occasionally observed, which we attribute to spin domains and/or fragmented states. In this poster, we will report on the investigation of these possibilities by QGM.