Profile
Greg Wallace
My CV
-
Education:
Fernwood school,
Bedford school,
University of Cambridge,
University of Bristol
-
Qualifications:
GCSE’s: maths, additional maths, FSMQ (i.e. more maths), physics, chemistry, biology, history, English literature, English language, French, Latin, Design and Technology
A-Levels: maths, further maths, physics, chemistry
University: BA (2:1) and Msci (2:1) from Peterhouse, Cambridge
-
Work History:
Summer jobs:
Milton Keynes Citizen Paper Round
Frosts Garden Centre: Sales assistant
Innovative Technology Ltd: Research assistant
Cavendish Laboratory Semiconductor Physics Group: Summer Student
Cavendish Laboratory Quantum Matter Group: Research AssistantActual jobs:
University of Bristol: PhD student -
Current Job:
Physics PhD
-
About Me:
I’m quite sporty and fence on the uni team. I REALLY love good food, particularly Indian and Italian. I like learning and understanding new things so I read and listen to podcasts a lot.
-
Read more
I live in Bristol, but quite far out! I’m quite sporty so I cycle in to work every day. I haven’t made the transition to lycra yet, hopefully I never will. My main sport is fencing and I’m on the uni team . I REALLY love good food, particularly Indian and Italian. I’m very curious and love learning about new things, I think almost anything can become interesting if you look closely enough or from the right perspective. As a result, I spend quite a lot of my spare time reading or listening to podcasts (Stuff To Blow Your Mind is my favourite). Otherwise I like playing computer games when I’d rather relax and unwind.
-
Read more
Superconductors (SCs) have some truly remarkable properties! This means they’re used in everything from MRI machines to quantum computers. However, they only work at very low temperatures, often a few degrees above absolute zero (-273.15*C). The temperature at which they start working is known as the critical temperature.
There are several types of SC, but they can be broadly split into type 1 and type 2. We understand how type 1 SCs work, but they have very low critical temperatures and require liquid helium to get cold enough. We don’t understand how type 2 SCs work, but some of them have much higher critical temperatures! By much higher we mean above the boiling point of liquid nitrogen (-195.8*C).
The problem of how high temperature SCs (HTCs) work has been confounding us for 30 years. Lots of the ‘easy’ experiments have already been done. In order to get a better picture of how these materials behave, so that we can better formulate a theory for how they behave, I am investigating high temperature SCs under extreme conditions. That means very high pressures, very high magnetic fields, and very low temperatures. By high pressure I mean 10 Giga-Pascals (GPa) which is about 100 times the pressure at the bottom of the Mariana trench, the deepest part of the ocean. The magnetic fields we use can be as high as 45 Teslas (T). The magnets that produce these sorts of fields have the power consumption of a small city. Higher fields of up to 100T can be achieved by only switching the magnet on for a very short time so it doesn’t melt. Sometimes we use special refrigerators to investigate temperatures a few hundredths of degrees above absolute zero. Needless to say working with these kinds of conditions is quite cool.
However, these conditions come with a few problems! Chiefly achieving these sorts of pressures requires using something called a diamond anvil cell.
We flatten the points of two diamonds so that the flat bit is a circle just under a millimetre in diameter. This is because to get high pressures we need a big force and a small area. We squash a metal disk with a small hole in it called a gasket between these two diamonds, which leaves a circle of roughly half a millimetre diameter to put the sample in.
The samples we use therefore have to be 200 micron (a fifth of a millimetre) squares which are very fiddly to work with! The samples are about the size of large grains of dust. As if that wasn’t bad enough
we also have to put contacts on them so we can actually measure electrical properties. This requires using silver paint to paint on contacts by hand, and these contacts need to be about 30 micron squares. You need very steady hands and a lot of patience.
-
My Typical Day:
I get up and cycle in to work. I check my emails for anything important before heading down to the lab. There I will be preparing samples, building equipment for my experiments, setting up new experiments, or monitoring existing ones as they can take several days!
-
Read more
Lots of things I do take place over several days, and sometimes they can be left alone so I often have several activities going on at once. Here I’ll describe the process of setting up a typical experiment, but I also perform computational calculations to complement my experiments
Firstly, I need to prepare my samples! These are grown in a sealed crucible which is smashed once the growth is completed. The resulting debris is composed of very flat and very thin crystals, along with a whole load of junk/bits of smashed crucible. The first task is picking out the best looking (shiniest and flattest) crystals under a microscope using a bit of plastic on the end of a cocktail stick.
These samples will be around a millimetre in size, and so need to be cut into the 200 micron squares I require. To do this I use a wire saw. This is just a very thin bit of tungsten wire coated in an abrasive paste that is hooked up to an electric motor. It takes about 15 minutes to make a single cut.
I should now have many lovely square samples. I need so many because they’re very easy to break, and the survivors can vary a lot in quality! Only the best will be used in the final experiment. Before that though I need to paint on contacts to attach wires to in the final experiment. Under a microscope, using a 10 micron wire taped to a cocktail stick, I have to apply silver paint to the corners of my square samples. This requires a steady hand and a lot of patience!
Next I ‘anneal’ my samples. This is a feature of the class of superconductors that I study, known as the cuprates. Their properties, including the critical temperature below which they superconduct, change dramatically depending on how much oxygen they have absorbed, and this is controlled by the annealing process. How long the annealing takes depends on the precise material you’re working with. It can take anywhere from a few hours to 3 weeks! The annealing furnaces are typically heated to 300-600*C depending on what properties you want your SC to have.
The samples are now ready. I carefully place them in the anvil cell with a small amount of liquid (usually glycerol) and seal it shut by applying pressure. I full the sample space with liquid to make sure the pressure is evenly distributed.
I’m now ready to attach the cell to a probe and stick it in a big cryo-cooled magnet to conduct an experiment!
-
What I'd do with the prize money:
I think I’d use it to fund travelling to schools to give talks on physics and quantum mechanics, maybe I would use a part of it to make props or experiments. I remember really enjoying learning about science beyond the curriculum when I was at school and I’d like to recreate that experience.
-
My Interview
-
How would you describe yourself in 3 words?
energetic, friendly, a bit intense (I asked my gf)
What did you want to be after you left school?
a scientist
Were you ever in trouble at school?
once got sent out of the room for eating a mint during lessons
Who is your favourite singer or band?
Barns Courtney
What's your favourite food?
All of it? There's a mutton biryani I had in Lucknow that was divine
If you had 3 wishes for yourself what would they be? - be honest!
Taller, darker, more handsome (asked gf again)
Tell us a joke.
What's the difference between ignorance and apathy? I don't know and I don't care
-