This Friday, May 3rd, The UQ Physics Colloquium is hosting Dr. Chris Baker, from the University of Queensland. Chris will talk about his research where with the help of optical force on superfluid films he explores ultralow Brillouin lasing and optically reconfigurable phononic landscapes.

The talk will be given at 11 am in Parnell (07) Rm 222.

Everyone is welcome to join.

Abstract: Two-dimensional superfluids exhibit rich quantum behavior such as topological quantum phase transitions. The key role in these phase transitions is played by quantized vortices, as acknowledged by the 2016 Physics Nobel Prize. However, none of the experimental techniques available so far have been capable of probing the microscopic dynamics of strongly-interacting 2D superfluids in real-time and resolving single quantized vortices.

In this colloquium, I will present an approach developed at UQ to probe the microscopic physics of 2D quantum fluids based on the optomechanical interaction between a nanometer-thick superfluid helium film and an optical Whispering Gallery Mode microcavity [1-3]. This method enables sound waves in the superfluid helium film to be confined to the surface of a microscale optical resonator, where they can interact with quantized vortices. The small area of confinement enhances the interactions between sound waves, vortices, and light.

In the presence of the background flow field created by a quantized vortex, the degeneracy between clockwise and counter-clockwise propagating superfluid sound waves is lifted. The presence of quantized vortices manifests therefore as a vortex-position dependent splitting in the sound modes, which affects each sound mode in a unique fashion [4]. By tracking this effect on multiple sound modes simultaneously, we can, therefore, track both the number of vortices, as well as their spatial distribution in real-time [5].

This capability provides a new tool to explore the microscopic behavior of 2D strongly interacting quantum fluids. Our results will enable a deeper understanding of 2D quantum phase transitions, dissipation mechanisms in 2D superfluid helium systems, quantum turbulence and the realization of optomechanics with quantized vortices.

At the end of the talk, I will also briefly present new results where we leverage the extreme compliance of the superfluid film to optical forces to demonstrate ultralow threshold Brillouin lasing and optically reconfigurable phononic landscapes.

About Physics colloquium

The Physics Colloquium series hosts a range of speakers from Australia and abroad. The series explores a variety of topics and everyone is welcome to come along. The seminars are open so there is no need to register your attendance.


222, Parnell Building 7

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