Exact diagonalization study for exotic quantum many-body states

Dr. Hongyu Yang

Tsinghua university

About the Speaker

Dr. Yang finished his Ph.D study in the center for advanced study, Tsinghua university (China) in 2006. Later he joined the Max Planck institute for the physics of complex systems in Dresden as a guest scientist. In 2008 he moved to technical university of Dortmund as postdoc. Three years later he started another long post-doc in the Swiss federal institute of technology in Lausanne (EPFL). His research interest is about frustrated magnetism, mainly computationally oriented. During the past research he also become expert of high performance computing.

Talk Introduction

In frustrated magnetism or correlated electrons system one often finds exotic properties which arise from collective behaviour of many-body states. We will present our study for novel quantum states emerged from many-body systems based on computational tools . 

We will present strong evidence of spin liquid phase of the half-filled Hubbard model on the triangular lattice. Based on perturbative continuous unitary transformation we derive a pure spin model as the effective model up to 12-th order strong coupling expansion. By lowering the value of U/t, the ground state of the resulting spin model undergoes a transition from three sub-lattice Néel order to spin liquid phase, revealed by exact diagonalization.

We also present the structure of the spectrum of antiferromagnetically coupled spin-1 bosons on a square lattice by analytic perturbation theory and exact diagonalization on very small clusters. The Anderson tower of states in the spectrum for this system clearly demonstrate the existence of nematic order.

The hpc implementation of exact diagonalization will be briefly discussed.     

时间：2015年7月20日上午10:30-11:30

地点：图书馆北馆二楼会议室

All are welcome！