Title: Scale invariance and type-B Goldstone modes

Speaker: Prof. Ian McCulloch, Tsing Hua University (Taiwan)

Time: 10:00 am, Apr.17th，2024

Venue: C302, New Science Building

Abstract: Ferromagnetic ground states have often been overlooked in comparison to seemingly more interesting antiferromagnetic ground states. However, both the physical and mathematical structure of ferromagnetic ground states are particularly rich. The highly degenerate and highly entangled ground states of the ferromagnetic spin-1 biquadratic model are scale invariant, originating from spontaneous symmetry breaking from SU(3) to U(1)×U(1) with two type-B Goldstone modes. The ground state degeneracies are characterized as the Fibonacci-Lucas sequences. Similarly rich physics occurs in other models, such as SO(4) spin-orbit model.

Bio: Professor Ian McCulloch received his PhD from the Australian National University, before moving to Europe for postdoctoral positions at the Instituut-Lorentz in The Netherlands, and RWTH-Aachen University in Germany. In 2007, he returned to Australia, to the University of Queensland, in Brisbane. Since August 2023, he is a Visiting Professor at National Tsing Hua University, Taiwan. His research interests are computational methods for quantum many-body systems using tensor network methods and DMRG. He was a pioneer of several key technical developments including non-Abelian symmetries, and the iDMRG method for translational invariant infinite systems. He has worked on applications in a variety of areas of condensed matter physics including atomic gases and topologically ordered states.