Nonlinear interrogation of quantum materials: why higher order response tells you more
The nonlinear response of quantum materials contains a wealth of information that is often hidden in the linear regime. Examples include second-harmonic generation (SHG) as a sensitive probe of electronic symmetry, and higher-order conductivities that provide insights into the quantum geometry of Bloch states and their Berry curvature distribution. Two-dimensional coherent THz and Raman spectroscopy are two other powerful nonlinear probes of low-energy excitations in quantum materials, which have recently become available in several labs. We review experimental progress and introduce an intuitive theoretical description of these methods in terms of Liouville quantum pathways. We then theoretically show how they can directly probe quasiparticle properties in the Kitaev honeycomb spin liquid and provide direct evidence for the emergence of localized Majorana excitations trapped by vison pairs.
About the speaker
Peter P. Orth is a theoretical condensed matter physicist who works on understanding and predicting properties of quantum materials. He explores quantum materials in and away from equilibrium using analytical field theory and quantum computing algorithms. Peter P. Orth is currently Professor in the Department of Physics at Saarland University, Germany. He is also Affiliate Associate Professor in the Department of Physics and Astronomy at Iowa State University and Contributing Scientist at Ames Laboratory. He received a Diploma in Physics at the Universität Heidelberg in 2007, and a Ph.D at Yale University in 2011 under the supervision of Prof. Karyn Le Hur. He held postdoctoral positions at the Karlsruhe Institute of Technology (KIT) and at the University of Minnesota. He served as deputy director of the “Center for the Advancement of Topological Semimetals” of the U.S. Department of Energy (DOE), where he investigated how to realize desired band topologies by controlling magnetic order and is a co-leader in the quantum algorithm thrust of the DOE National Quantum Initiative Center on “Superconducting Quantum Materials and Systems” (SQMS), where he develops and implements quantum computing algorithms for many-body systems.
This year, the physics colloquium has a new format:
- Onsite at Campus Limpertsberg, where you will have the opportunity to meet the speaker over lunch. The catering is offered only to the registered participants from noon in the BSC Hall.
- Online – through Webex – to allow you to listen to the talk in case you are travelling or cannot make it on-site at Campus Limpertsberg.
Meeting number: 2780 938 4373
Meeting password: 6aKyDHDDU86
Registration
Please register for the lunch before 14 February 2024.