EPSRC Reference: 
EP/V03832X/1 
Title: 
Controlled Creation and Dynamics of nonAbelian Vortices and Topological Processes in spinor BoseEinstein condensates 
Principal Investigator: 
Borgh, Dr MO 
Other Investigators: 

Researcher CoInvestigators: 

Project Partners: 

Department: 
Chemistry 
Organisation: 
University of East Anglia 
Scheme: 
New Investigator Award 
Starts: 
01 November 2021 
Ends: 
31 October 2024 
Value (£): 
378,760

EPSRC Research Topic Classifications: 

EPSRC Industrial Sector Classifications: 

Related Grants: 

Panel History: 
Panel Date  Panel Name  Outcome 
21 Apr 2021

EPSRC Physical Sciences 21 and 22 April 2021

Announced


Summary on Grant Application Form 
Vortices in fluids are familiar from everyday life, appearing when we stir a cup of tea or drain a bath tub. In superfluids, which flow without viscosity, vortices take on properties arising from the underlying quantum mechanics and behave very differently from what we are used to. Perhaps paradoxically, the consequence is that the fundamental properties of the vortices become relatively insensitive to details of how the particles in the superfluid interact. Instead, the essential features of vortices are understood generically from internal symmetries of the physical state using topology, the field of mathematics that studies what remains unchanged about an object as it is twisted or distorted. Phenomena arising from topology are therefore often universal across seemingly disparate parts of physics and have attracted considerable attention, highlighted by the 2016 Nobel Prize.
Here we will apply theoretical methods to study particular vortices in spinor BoseEinstein condensates (BECs). This is a superfluid state of matter that appears in certain atomic gases cooled to near absolute zero using techniques that do not freeze out the atoms' quantummechanical spin. The spin comes at integer values. We are interested in atoms where the spin is equal to 2, for the reason that the vortices that then appear can be what is called nonAbelian. Vortices are categorised by socalled topological charges. One charge can be added to another, but this addition does not always follow the familiar rules of arithmetics. For nonAbelian vortices, the order matters: A + B is not the same as B + A. This leads to highly counterintuitive vortex interactions, such that if two vortices collide, they must form a new vortex that continues to connect them even as they move apart. This is not a mere curiosity: analogous objects, described by the same mathematics, can appear also in liquid crystals or in cosmological theories. It is no surprise then that a central goal for experiments is the controlled creation of nonAbelian vortices in the highly accessible spinor BECs, which could act as emulators of physics of much wider importance.
The central task of our project is to provide the theoretical underpinnings for this effort. Several techniques exist for controlled creation of vortices in BECs. However, these cannot be used directly to create vortices that show the nonAbelian properties. We will propose specific protocols for the creation of such vortices and vortex ensembles. We will also, using computer simulations, determine what these vortices look like once they have been allowed to evolve. We can then provide the observable signatures necessary for interpreting the experiments. For this effort to succeed, the work will be done in close contact with experimental project partners at Amherst College, Massachusetts, USA.
We will push the computational limits by simulating dynamical scenarios where topological defects such as vortices determine the physics. For example, the interface between two distinct phases of the same spinor BEC is analogous to similar boundaries in superfluid helium3. We will determine what vortices are produced when interfaces collide. Importantly, this represents a laboratory scale simulation of processes analogous to those proposed in theories of the early universe. What role do nonAbelian defects play? What can spinor BECs teach us about such processes in general? Defects are also produced when superfluids pass through phase transitions, from one state to another (a familiar example is the freezing of water into ice). Such processes are enormously important also in other quantum systems as well as in cosmology. We will seek to determine whether nonAbelian vortices are produced in the phase transition and, if so, what differences that implies to phase transitions in systems with only Abelian vortices. Again we are motivated by the intriguing prospect of simulating cosmological phenomena in the laboratory.

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