Superfluidity in the presence of dipolar interactions

In the study of many-body quantum systems, two of the key tuning parameters are the nature of interactions between the particles and the geometry in which the particles are confined.

This project will use an ultracold gas of Erbium atoms, which due to their large magnetic dipole moment interact via longer range dipole-dipole interactions as well as the more usual contact interactions, to investigate the effect of long-range dipole interactions on superfluidity.  The initial part of the project will involve designing and implementing a homogeneous quasi-2D trap for ultracold Erbium atoms before:

  • Exploring the appearance and consequences of the ‘roton-like’ excitation spectrum that is expected in a dipolar gas for such a trapping geometry. This roton feature, characterised by a minimum in the dispersion relation of elementary excitations, is one of the defining attributes of superfluid liquid helium. This project will seek to directly measure the feature in a dipolar gas and then use the tunability of the cold atom environment to more fully map out and understand its consequences for superfluidity.
  • Searching for a supersolid phase mediated by the long-range interactions.  A supersolid phase is one in which there is both long range spatial ordering (like a solid) and long range phase coherence (like a superfluid).


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Exploring out-of-equilibrium many-body quantum systems

The scientific understanding of non-equilibrium phenomena is generally less advanced than that of the related equilibrium states. Consider for example an isolated many-body quantum system; there are many questions that are still far from answered: What determines whether a quantum system will equilibrate? How does a quantum system equilibrate? Does equilibration always mean thermalisation? What is the role of temperature? As well as being of fundamental scientific interest, these and many other questions will be crucial for future technologies such as quantum computing, where the dynamical response of the system to external operations is a key consideration. For example, dynamical considerations may place a speed limit on such operations.

This project which forms part of the DesOEQ (Designing out of equilibrium many-body quantum systems) programme grant and will explore these issues using an ultracold gas of Erbium atoms.  Topics to be covered will include studying the effect of long-range interactions on critical phase transition dynamics and studies of periodically driven systems and turbulence.



Dual species Erbium and Potassium machine: polarons and beyond

A single impurity interacting with a quantum bath is a simple (to state) yet rich many-body paradigm that is relevant across a wide sweep of fields from condensed matter physics to quantum information theory to particle physics. The aim of this project is to experimentally explore this physics using the highly controllable platform of a ultracold bath of Erbium atoms in which potassium impurities can be imbedded. The special feature of Erbium atoms is their large magnetic dipole moments which result in long-range and anisotropic dipole-dipole interactions in addition to the short-range contact interactions more normally seen in cold atom systems. This opens new avenues in a range of topics from polaron physics to information flow in open quantum systems.