Low Temperature Physics
We perform experiments on superfluids and other materials with applications in areas such as nanoelectronics, cosmology and turbulence.
The group has a strong international reputation for performing state-of-the-art experiments at the lowest achievable temperatures. Our custom made dilution refrigerators, built in-house, achieve world-record low temperatures. We have pioneered several innovative approaches, including:
- 'Lancaster-style' demagnetisation stages to cool superfluid helium-3 to record low temperatures
- 'heat-flush' procedures to produce highly purified helium-4
- ion transport measurement methods for quantum fluids
- novel NMR systems
- various mechanical oscillator techniques which provide extremely sensitive thermometry and bolometry at microkelvin temperatures
We are well known for providing these sub-millikelvin low temperature environments with advanced in-house cryogenic engineering, and for our accompanying expertise in ultra-sensitive measurement techniques and the development of specialised instrumentation.
Creating, controlling and exploiting the ultra-low temperature environment has proven crucial for the research and development of quantum-enhanced devices. Our platform technology provides the extreme cold and isolation necessary to probe the subtle quantum behaviours that are otherwise hidden by thermal fluctuations or external disturbance.
We have a broad research portfolio in low temperature physics and specialise in quantum fluids and solids research. We have performed ground-breaking analysis on numerous topics, including
- superfluid analogues of cosmological processes
- ion and vortex ring dynamics
- ballistic quasiparticle beams
- exotic superfluid spin phenomena
- superfluid phase nucleation
- phase boundary dynamics
- wave turbulence
- quantum turbulence
- Cooling and sensitive measurement techniques
- Quantum fluids and solids
- Superfluid 3He
- Superfluid 4He
- Properties of materials at ultra-low temperatures
- MEMS and NEMS devices at low temperatures
- Extremely cold devices and associated quantum technologies
- Development of sensitive measurement techniques
Nanomechanical devices in quantum fluids
Dr Sergey Kafanov
In this project, the PhD student will work within the ULT group to investigate the behaviour of Micro-Electro-Mechanical (MEM) and Nano-Electro-Mechanical (NEM) resonators in the vacuum and superfluid 3He at world-record low temperatures. There is a growing demand for cooling micro and nano-electromechanical oscillators down to submillikelvin temperatures, and existing research indicates that 3He superfluid is the best available coolant to achieve this. The goals of the project are to understand and overcome existing cooling restrictions and to reach submillikelvin temperatures. Furthermore, MEM and NEM beams could be used to probe superfluid 3He at various sub-gap frequencies and length scales comparable to the coherence length of the condensate. This would have very far-reaching scientific and technological impacts.
Superfluid 3He far from equilibrium
In this project, the PhD student will work within the ULT group to study non-equilibrium phenomena in a well-known system with an established theoretical framework - superfluid 3He. Coherent condensates (or at least those to which we have experimental access) are fragile objects that only exist at the extremes of very low temperatures. We can study condensates over a wide range of conditions from the virtually zero-entropy zero-temperature quiescent state through to the regime where we have the destruction of coherence. It is "common knowledge" that when we move a scatterer through a superfluid, then at some critical velocity the superfluidity should catastrophically break down and return the system to the normal state. Recently, we have shown at Lancaster that this does not happen in superfluid 3He up to velocities well above the accepted Landau critical value. This was quite unexpected. Using for the first time the powerful combination of nuclear magnetic resonance with steady superflow in 3He at ultralow temperatures we aim to investigate several emergent phenomena such as quantum critical phase transitions between different superfluid phases.
Quantum turbulence and vortex pinning in superfluid 4He
Turbulence, we all know, is ubiquitous, impinging forcefully, not only on human activity but also overall nature on scales from the nuclear to the cosmological. That said, it is almost embarrassing that we still have no adequate theory of turbulence. This is where studies of quantum turbulence, the version of turbulence only occurring in superfluids, can play a part. Quantum turbulence is very different as there is no viscous dissipation since pure condensates do not support viscous forces. Nevertheless, the most fundamental difference arises from the phase coherence in the condensate that ensures that any vortices are singly quantised and thus identical. In consequence, we can regard such an ensemble as providing an ideal “atomic theory” of turbulence.
In this project, the student will work within the ULT group to study quantum turbulence and vortex pinning in superfluid 4He using torsional oscillator techniques. All earlier experiments on the generation of quantum turbulence by oscillating structures have used objects with convex surfaces; the flow around them is classically unstable at a low velocity, and the two expected transitions to turbulence are not distinguishable. In contrast, in this project the helium will be inside a pill-box that oscillates about its axis, thus eliminating all flow over convex surfaces. The two transitions should then be well separated and identifiable as characteristic increases in damping. The fundamental properties of the remanent vortices themselves will be studied, by investigating their pinning to microscopic protuberances.
Visualisation of Quantum Turbulence via Andreev Reflection in superfluid 3He
Turbulence, we all know, is ubiquitous, impinging forcefully, not only on human activity but also overall nature on scales from the nuclear to the cosmological. That said, it is almost embarrassing that we still have no adequate theory of turbulence. This is where studies of the quantum turbulence, the version of turbulence only occurring in superfluids, can play a part. Quantum turbulence is very different as there is no viscous dissipation since pure condensates do not support viscous forces. Nevertheless, the most fundamental difference arises from the phase coherence in the condensate that ensures that any vortices are singly quantised and thus identical. In consequence, we can regard such an ensemble as providing an ideal “atomic theory” of turbulence.
In this project, the student will work within the ULT group to study numerically and experimentally visualization of quantum turbulence in superfluid 3He. We have pioneered the non-invasive detection of vortices by a surprisingly simple method which uses the Andreev reflection of quasiparticle excitations from the flow field circling each vortex. Our advanced vortex-detection techniques using mechanical oscillators provide knowledge of the turbulent behaviour that is simply not accessible in other systems. The measurements will be contrasted with computer simulations of moderately dense, three-dimensional, quasiclassical vortex tangles and the Andreev reflection of thermal quasiparticle excitations by these tangles. The research project will also address the question of how the Andreev reflectivities can distinguish quasiclassical and ultraquantum regimes of quantum turbulence, revealing their nature and signature properties
Quantum electronics for an axion detector
Supervisors: Yuri Pashkin, Ian Bailey, Edward Laird
One of the greatest challenges in physics is to identify the dark matter that makes up 80% of our galaxy’s mass. Among the leading candidates is a hypothetical particle called the axion. This is a well-motivated addition to the Standard Model but is very difficult to detect because it is predicted to interact feebly with ordinary matter. This project will develop quantum amplifiers in a new UK experiment that will search for axions.
If axions exist, then in a strong magnetic field they can decay into photons with frequencies proportional to the axion mass. However, the resulting electromagnetic signal is expected to be extremely weak – comparable to intrinsic quantum fluctuations, and weaker than thermal radiation except at the coldest accessible temperatures. This project aims to detect evidence of axions by developing and using superconducting amplifiers that can approach and ultimately exceed the standard quantum limit of detection sensitivity.
Lancaster Physics ranks among the highest-rated research departments in the UK. In the Low Temperature Physics and Quantum Nanotechnology groups, we carry out experiments in condensed matter physics and quantum electronics in some of the coldest and most isolated environments in the universe. We recruit highly motivated graduates in physics or related fields with curiosity, grit, and a passion for making new discoveries through experiment. We have a strong track record of high-profile publications by PhD students. We have access to excellent facilities for nanofabrication, electronics, and low-temperature measurement. These include:
- The state-of-the-art cleanroom of Lancaster’s Quantum Technology Centre.
- New cryogen-free dilution refrigerators optimised for high-speed quantum electronics.
- Extensive collaborations with low-temperature and particle physicists in Lancaster and beyond.
The student will work within the Quantum Sensors for the Hidden Sector Collaboration, which is an STFC-funded project to search for axions and axion-like particles (ALPs) using advanced quantum electronics and quantum measurement techniques. The collaboration works with the Axion Dark Matter Experiment (ADMX) in the USA, which currently leads the world in sensitivity to dark matter axions. We aim to develop a novel high-frequency axion target to be incorporated into the existing ADMX apparatus, as well as developing our own cutting-edge research instrumentation for axion and ALP research in the United Kingdom. The student will have the opportunity to develop research experience in a range of areas across quantum electronics, microwave electronics, cryogenics, magnetic field physics, quantum systems theory, and particle theory and phenomenology. They will join the collaboration as it embarks on this exciting new programme of inter-disciplinary fundamental research in the UK.
Nanoelectromechanical sensors for magnetic resonance microscopy
Supervisor: Edward Laird
Magnetic resonance imaging (MRI) is a powerful and non-invasive technique for looking inside the human body. If we could make a microscope that works on the same principle, we would be able to do something that is presently impossible – to look inside cells, viruses, and potentially even individual molecules and identify the atoms from which they are made. Unfortunately, MRI machines cannot simply be made smaller, because as their radio antennas are shrunk they become less sensitive. For this reason, the resolution of conventional MRI is still far below that of other kinds of microscope.
To develop an MRI microscope, we need to develop a new kind of device that measures the same effect with much higher resolution. Such an approach is magnetic resonance force microscopy. In this technique, a tiny nano-magnet is attached to a delicate mechanical spring and positioned as close as possible to the specimen being measured. As the nuclei in the specimen precess, their magnetic field deflects the nano-magnet, thus creating a measurable signal.
To construct a microscope based on this principle is still a formidable challenge. For each nucleus in the specimen, the force exerted on the nano-magnet is roughly one zepto-Newton. We aim to detect such a force by using the lightest, most delicate spring that can be fabricated – a single carbon nanotube. This project will develop nanotube force sensors and the associated quantum electronics to measure them. The two central physics challenges are to attach a nano-magnet to a nanotube spring and to measure its tiny deflection. To overcome them, we seek highly motivated graduates in physics or related fields with curiosity, grit, and a passion for making new discoveries through experiment.
We have a strong track record of high-profile publications by PhD students. We have access to excellent facilities for nanofabrication, electronics, and low-temperature measurement. These include:
- The state-of-the-art cleanroom of Lancaster’s Quantum Technology Centre.
- New cryogen-free dilution refrigerators optimised for high-speed quantum electronics and equipped with ultra-sensitive superconducting amplifiers.
- Extensive collaborations with low-temperature and quantum physicists in Lancaster and beyond.
Within this project, you will work in the Low Temperature Physics and Quantum Nanotechnology groups at Lancaster. You will receive a thorough training, supported by state-of-the art equipment, in quantum electronics, low-temperature physics, nanofabrication, and scientific communication. Through your research in this project, you will have the opportunity to contribute to a physics-based technology with profound potential in materials science and biology.
The coldest liquid in the Universe
Dr Dmitry Zmeev
We will attempt to achieve the lowest temperature for any liquid. The project is concentrated around developing and demonstrating a new technique for cooling superfluid Helium-3. By utilising the nuclei of solid Helium-3 adsorbed on the surface of aerogel as a refrigerant in the adiabatic demagnetisation process, we will try and cool the superfluid to well below 100 microkelvins. Measuring such low temperatures is an arduous task. We will develop a method based on creating a Bose-Einstein Condensate of magnons within the superfluid and measurement its decay due to the very few thermal excitations remaining in the liquid. If successful, we will seek to apply the developed technique to cooling other systems, such as electrons in quantum devices, where lower temperature means longer coherence times.
SQUID noise thermometry for nanodevices at submillikelvin temperatures
Dr Viktor Tsepelin, Dr Jonathan Prance
In this project, the PhD student will work within the Ultra Low Temperature group to design, build and investigate Superconducting Quantum Interference Device (SQUID) based noise thermometry for nanodevices. There is a huge demand for cooling micro and nano-sized samples down to submillikelvin temperatures and ULT currently holds world record on cooling electrons in nano samples. Cooling is accomplished either by submerging nano samples in liquid helium-3 or by the direct adiabatic demagnetization of nano samples. The outstanding challenge is to measure temperature accurately, reliably and fast. Unprecedented SQUID sensitivity will permit us developing a non-contact thermometer measuring magnetic noise raising from the oscillations of the electrons in the metallic nano samples. The amount of noise is temperature-dependent and can be calculated from the first principles, which allows the thermometer to be self-calibrated. We aim to use cross-correlation between SQUID two-channels to eliminate any noise from the SQUID amplifier thus making it operational down to submillikelvin temperatures (~50 microkelvins).
We run training sessions for postgraduate students throughout the year, covering both specific low temperature technology and more general research skills.
You can also attend a series of lectures jointly organised with the University of Manchester. These will allow you to meet students from other institutions, as well as being taught new material that may be of use to you in future years.
The nature of the training is dependent on your project requirements and the skills you will need to make progress in your work. You will engage in a continual discussion with us to ensure that we provide the most relevant and practical training. The Faculty of Science and Technology, ISS, and the Library offer additional training.
You will receive training in a wide range of formats on topics of interest to your project:
- North West England Solid State lectures organised by Manchester and Lancaster universities
- Physics of superfluids and superconductors
- Essential cryogenic safety and safe handling of cryogenic liquids
- Operation of sophisticated low temperature refrigeration equipment
- Fabrication of NEMs and MEMs devices
- Experimental instrumentation design and construction
- Innovative measurement techniques
- Data acquisition techniques
- Data analysis and computer-based simulation techniques
- Preparation of manuscripts, posters and oral presentations
You could attend a variety of scientific conferences, allowing you to present your work. If necessary, you will receive additional support and advice on the preparation of posters and oral presentations. You also have the chance to develop their presentation skills via participation in the Department’s public understanding of physics outreach programme.
New tutorials, workshops and conferences include:
- Annual Institute of Physics Low Temperature Techniques Course
- Annual European School and Workshop in Cryogenics and Quantum Engineering which has been running since 2002
- EuHIT School on Turbulence provides an opportunity for high-quality lectures on experimental techniques, numerical methods in fluid dynamics and the theory of turbulence
- Triennial International Conference on Low Temperature Physics
- Satellite LT28 on Ultralow Temperature Physics: ULT 2017 Frontiers of Low Temperature Physics
- Quantum Fluids and Solids Conference series