PhD Studentships Lancaster University Physics Department United Kingdom

Supervisor: Rostislav Mikhaylovskiy

 

Finding a fundamentally new way for data processing in the fastest and most energy efficient manner is a frontier problem for applied physics and technology. The amount of data generated every second is so enormous that the heat produced by modern data centres has already become a serious limitation to further increase their performance. This heating is a result of the Ohmic dissipation of energy unavoidable in conventional electronics. At present, the data industry lacks a solution for this problem, which in future may contribute greatly to the global warming and energy crisis.

 

An emerging alternative approach is to employ spin waves (magnons) to realize waveform-based computation, which is free from electronic Joule heating. However, the present realization of this approach, called magnonics, uses electric currents to generate and modulate magnons. In the course of this PhD project we will work towards replacement of the current by light using antiferromagnetic materials, in which spins precess on a picosecond (one trillionth of a second) timescale and strongly couple to electro-magnetic waves [1]. Yet, the antiferromagnetic THz magnons remain practically unexplored.

 

To excite THz magnons we will use ultrashort strong electro-magnetic fields produced either by table-top ultrafast lasers or by electron bunches at electron-beam facilities of Cockcroft Institute. We will push the driven spin dynamics into strongly nonlinear regime required for practical applications such as quantum computation or magnetization switching [2]. We will investigate nonlinear interaction of intense and highly coherent magnons with an eye on reaching regimes of auto-oscillations, nonlinear frequency conversion and complete magnetization reversal.

 

This interdisciplinary project at the interface between magnetism and photonics offers training in ultrafast optics, THz and magneto-optical spectroscopies as well as in physics of magnetically ordered materials. Also there will be opportunities for travel and experiments using THz free-electron laser facilities such as FELIX (Nijmegen, Netherlands) and TELBE (Dresden, Germany). 


Quantum nanomechanics with vibrating carbon nanotubes
Supervisor: Dr Edward Laird

 

We are seeking two talented and highly motivated PhD candidates for a new experimental project in quantum electronics and nanomechanics. The project uses the outstanding force-sensing properties of carbon nanotubes to study quantum physics in regimes that have not yet been accessed experimentally.

 

One project focuses on measuring the effects of quantum superposition in an electromechanical circuit. The particle under test will be a vibrating carbon nanotube, consisting of approximately one million nucleons. To study its quantum behaviour, you will incorporate it first into a superconducting junction, and then into a superconducting qubit. The ultimate aim is to realise a new kind of matter-wave interferometer, in which the wavefunction of the entire nanotube is separated, recombined, and measured. This would dramatically push the boundary of quantum superposition from the realm of molecules towards the realm of fabricated objects.

 

The second experiment will study one of the most fascinating known manifestations of collective quantum behaviour, namely superfluidity in helium. There is at present no experimental tool to measure superfluids on the mesoscopic scale, i.e. between the size of atoms and the superfluid coherence length. A vibrating nanotube, working as a tiny moving-wire viscometer, can measure superfluidity on this tiny scale. You will measure viscous damping first in the well-understood superfluid helium-4, and then in its exotic cousin helium-3, whose emergent behaviour mimics fundamental properties of our universe.

 

We seek candidates with an excellent academic record in physics or a related field, equivalent to at least a first-class degree from Lancaster, and a good grounding in condensed-matter physics, quantum mechanics, and electromagnetism. Specific experimental skills are not required, but self-motivation and a can-do attitude are. For suitable candidates, full funding is available regardless of nationality.

 

Students will have access to the excellent low-temperature measurement and nanofabrication facilities of Lancaster University Physics Department, including new equipment dedicated to this project. Research is funded by the European Research Council as part of the €2.7M project “Vibrating carbon nanotubes for probing quantum systems at the mesoscale”.


Noise Thermometry with a focus on SQUIDS and nanodevices operating at millikelvin temperatures
Supervisors: Dr Viktor Tsepelin & Dr Jonathan Prance

 

There is a huge demand of cooling micro and nano-sized samples down to submillikelvin temperatures and Lancaster Low Temperature Group is at the frontier of cooling electrons in nanosamples. Cooling is accomplished either by submerging nanosamples in liquid helium-3 or by direct adiabatic demagnetization of nanosamples. The outstanding challenge in these experiments is to measure temperature accurately, reliably and fast. Unprecedented SQUID sensitivity will enable us to develop a non-contact thermometer measuring magnetic noise, arising from the thermal motion of electrons in metallic nanosamples.

 

The project will be undertaken in the Lancaster Low Temperature Group and Quantum Technology Centre. The work is experimental and will involve fabricating devices, cooling them to millikelvin temperatures and performing measurements. Fabrication will be done on site using state-of-the-art nanofabrication facilities available in the LQTC cleanroom. The Low Temperature Group has several dilution refrigerators where measurements will be conducted.


Long wavelength (>1400 nm) GaSb quantum ring VCSELs for consumer applications
Supervisor: Prof Manus Hayne
EPSRC iCASE 4 year studentship

 

Vertical-cavity surface-emitting lasers (VCSELs) are high-speed, compact (low cost) laser diodes used in laser printing, datacoms and other applications. However, their implementation in the sensing and 3D imaging functions of smartphones has recently transformed the VCSEL market.

 

The project will build on successful collaborative work between IQE and Lancaster developing telecoms wavelength (1300 nm) GaSb quantum ring (QR) VCSELs. The objective is to push the emission wavelength further into the infrared to reach the crucial >1400 nm wavelength range for ‘eye-safe’ VCSELs to be used in the next generation of proximity sensing, gesture recognition, 3D imaging and LiDAR devices for consumer and automotive applications. The student will receive comprehensive training in both academic and industrial contexts, leading to the design, growth, processing and operation of >1400 nm VCSELs and VCSEL arrays.


Superconducting Quantum Devices with a focus on Josephson parametric amplifiers operating at millikelvin temperatures
Supervisor: Prof Yuri Pashkin

 

Quantum technologies require the preparation, manipulation and readout of quantum states that are sensitive to noise and prone to decoherence. One of the most promising approaches is based on using superconducting circuits that benefit from extremely low dissipation and well established fabrication process. The challenge in the field is handling quantum states with utmost care and amplifying extremely weak signals using advanced instrumentation. Recent developments depend on the availability of cryogenic amplifiers with sufficient gain and bandwidth, and with an added noise level that is only limited by intrinsic quantum fluctuations. Existing semiconductor and superconducting amplifiers all suffer from compromises in one or more of these critical specifications.

 

The Josephson Travelling Wave Parametric Amplifier (JTWPA) (A.B. Zorin, Phys. Rev. Applied 6, 034006 (2016)) is predicted to outperform the existing versions of parametric amplifiers in gain, bandwidth and simplicity of construction. The JTWPA will be integrated with the single-Cooper-pair transistor to facilitate early uptake by the user community.

 

The project will be undertaken in the Lancaster Quantum Technology Centre. The work is experimental and an essential part of the project will be device fabrication using state-of-the-art nanofabrication facilities available in the LQTC cleanroom. The student will gain experience of working in a cleanroom environment and acquire practical skills in electron-beam and photolithography, thin-film deposition and plasma processing. They will be assisted by the experienced dedicated cleanroom technicians and academic staff who have expertise and hands-on experience in nanofabrication. Device characterisation will be performed in a cryogenfree dilution refrigerator equipped with microwave measurement lines and cold amplifiers.

 

To apply for these studentships please click on the Apply button above or contact our postgraduate admissions staff at py-pgadmiss@lancaster.ac.uk  You can also apply directly at http://www.lancaster.ac.uk/physics/study/phd/ stating the title of the project and the name of the supervisor in your application.

 

All projects start on 1 October 2019 and are for 3.5 years unless stated otherwise. All studentships include a stipend with fees paid.

 

The Physics Department is holder of Athena SWAN Silver award and JUNO Championship status and is strongly committed to fostering diversity within its community as a source of excellence, cultural enrichment, and social strength. We welcome those who would contribute to the further diversification of our department.


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