报告题目：含有轨道角动量的超冷原子：复数隧穿，本征态和自旋模型 (Ultracold Atoms Carrying Orbital Angular Momentum: complex tunnelings, edge-states and spin models)
报 告 人：Prof. Verònica Ahufinger (Department of Physics, Universitat Autònoma de Barcelona, Spain)
报告时间：2018年4月4日（周三）10：00
报告地点：校本部G309
邀请人：张永平， 陈玺
报告摘要：
In this talk, we will show that ultracold atoms carrying orbital angular momentum open a very rich scenario. Specifically, we will demonstrate that complex tunneling amplitudes appear naturally in the dynamics of orbital angular momentum states for a single ultracold atom trapped in two-dimensional (2D) systems of sided coupled cylindrically symmetric identical traps [1]. In a triangular ring configuration, complex tunnelings lead to the possibility of engineering spatial dark states, which allows manipulating the transport of angular momentum states via quantum interference. We will show that robust edge-like states [2] of a single ultracold atom in a 2D optical ribbon can be engineered within the manifold of local states carrying one unit of angular momentum of the sites of a diamond-chain optical lattice. The existence of these ELS is due to quantum interference effects, and they can be intuitively constructed as combinations of three-site spatial dark states (SDS). These states are very robust against different types of defects and form a zero-energy flat band. We have checked that the angular momentum degree of freedom opens a gap in the band structure which is not present in the absence of OAM, resembling the effect of a net flux through the plaquettes [3]. In a finite size system, we identify states that lie inside the energy gap and are localized at the edge of the chain. Through a series of exact mappings to other models, we show that these states are topological [4]. In addition, in the limit of unit filling and strong interactions we study [4] the mapping of the system into a spin-1/2 model which offers an alternative platform to obtain a quantum simulator of the Heisenberg XYZ model with bosons in excited modes [5].
[1] J. Polo, J. Mompart, V. Ahufinger, Phys. Rev. A 93, 033613 (2016).
[2]G. Pelegrí, J. Polo, A. Turpin, M. Lewenstein, J. Mompart, V. Ahufinger, Phys. Rev. A 95, 013614 (2017).
[3] A. A. Lopes and R. G. Dias, Phys. Rev. B 84, 085124 (2011).
[4] G. Pelegrí, A. M. Marques, R. G. Dias, J. Mompart, V. Ahufinger, A. J. Daley, in preparation.
[5] F. Pinheiro, G. M. Bruun, J.-P. Martikainen, and J. Larson, Phys. Rev. Lett. 111, 205302 (2013).
