Frustration induced chiral supersolidity in ultracold dipolar gases

Quantum condensed matter physics deals with macroscopic and microscopic properties of matter by making use of the laws of electromagnetism, statistical mechanics and other physics theories, with the aim of describing the behavior of quantum matter. The models developed are useful in many different frames, as this theory often overlaps with atomic physics, chemistry and biophysics. The development of quantum mechanics allowed for the expansion of this discipline into the quantum world, in particular for the study of exotic phases of matter, whose existence is made possible by the counter-intuitive rules of quantum mechanics. Among these, supersolids are certainly one of the most interesting and strange phases. This state of matter is characterized by a broken translational symmetry, causing a periodic modulation in the local density of particles as in solids, but it also exhibits a partial frictionless flow of particles, typical of a superfluid state. The theoretical prediction of supersolidity dates back to the 1960s and it anticipated the experimental confirmation by many decades, as this was achieved only in the second half of 2010s, thanks especially to the advancements in the control of ultracold dipolar gases. At the moment, theoretical predictions and experimental observations are mainly focused to mean field regimes: the possible presence of this state of matter in a deeply quantum regime remains much less understood. Moreover, chirality is a property present in many different fields of science and it can play a prominent role in several areas of quantum physics. It is the consequence of an asymmetry that causes a system or a phenomenon not to be identical to its mirror image. We are particularly interested in the observation of chiral phases induced by the presence of geometrical frustration in systems of interacting quantum particles, where the spontaneous breaking of the time-reversal symmetry occurs. In order to accurately consider the role of quantum fluctuations, we use the Density Matrix Renormalization Group algorithm. The latter allows for the extraction of the ground-state properties of the one-dimensional frustrated extended Bose-Hubbard model. In particular, in our analysis we unveil the presence of a novel quantum phase of matter, namely the chiral lattice supersolid. This exotic quantum state features a density-modulated structure together with properties of superfluids. In addition, time-reversal symmetry is spontaneously broken and finite currents are present between sites, allowing us to identify this supersolid phase as chiral. Such a state of matter can be created in experiments by confining dipolar atoms, which have to be cooled down to extremely low temperatures, in an optical lattice, obtained by means of a suitable combination of light beams.