Thursday, April 15, 2021

Fifty years ago: three big discoveries in condensed matter

For the marketing plan for my Very Short Introduction, I was recently asked whether there were any significant anniversaries happening in condensed matter physics (and associated conferences). This is not something I normally think about.

I realised that fifty years ago there were three big discoveries. All eventually led to Nobel Prizes. Each discovery had a profound effect on the formation of condensed matter as a distinct discipline built around a few unifying concepts. At the time the discoveries and ideas appeared quite independent, but there are deep connections between them.

Renormalisation group and critical phenomena

In 1971 Ken Wilson published two PRB's laying the foundations, followed by two PRLs in 1972. He received the Nobel Prize in 1982. This work had many implications and applications. 

Explained universality in critical phenomena.

Highlighted how spatial dimensionality changes physics.

Illustrates why effective Hamiltonians work (so well).

Showed the power of quantum field theory techniques.

Defined concepts of scaling and fixed points.

Superfluidity in liquid 3He

In 1972,  Osheroff, Richardson, and Lee reported new phase transitions in liquid/solid 3He. Tony Leggett identified these as due superfluid phases and also identified the order parameters. The experimentalists shared the Nobel Prize in 1996 and Leggett in 2003. The discovery was significant for many reasons, beyond just being a new state of matter.

It provided a rich example of a state of matter with multiple broken symmetries. The order parameter has eighteen components, which can be viewed as a combined superfluid, ferromagnet, and liquid crystal.

The rich order parameter led to an exploration of diverse topological defects, from vortices with magnetic cores to boojums. This highlighted the concepts of broken symmetry, rigidity, and topological defects.

This was the first example of an unconventional fermionic superfluid. Specifically, it could be described by BCS theory, but not with s-wave pairing nor with the pairing mechanism of the electron-phonon interaction in elemental superconductors. This showed the adaptability of BCS theory. It laid the groundwork for understanding unconventional superconductivity in heavy fermions, organics, and cuprates.

Berezinskii-Kosterlitz-Thouless phase transitions

In 1971 Berezinskii published his paper, and Kosterlitz and Thouless published papers in 1972 and 1973. This work was significant for reasons including the following.

It showed states of matter and phase transitions were qualitatively different in two and three dimensions.

New concepts such as topological order, quasi-long-range order, essential singularities, and defect-mediated phase transitions were introduced.

Like that of Wilson, this work highlighted universality. There were connections between superfluids, superconductors, and XY magnets.

Scaling equations provided insight.

Kosterlitz and Thouless were awarded the Nobel Prize in 2016

We should celebrate!

Wow! Quite the Golden Jubilee!

Does anyone know of any conferences, events, or books that are planned to mark these anniversaries?

Monday, April 12, 2021

Time management and stress reduction

I am not the greatest manager of my time. I am easily distracted and too often ruled by the tyranny of the urgent. I let the good become the enemy of the excellent. I look at my email too often...

Here are just a few points that I do find helpful to keep in mind and act on. They not only lead to better use of time but also reduce stress. I struggle with all of them.

1. It can wait.

We live in an urgent world with many people and tasks demanding immediate attention. There are some very rigid deadlines, such as for most grant applications. However, there are many other tasks such as submitting a paper, checking an experiment, replying to an email, ... that can wait for another today. It is time to log off, literally and mentally and relax. The world will not fall apart if you wait another day, week, or even month.

2. Delegate

Do I personally need to do this task or take on this responsibility? Is there someone else who is able and available to do it instead? Might they actually do it better than me? Even if they might not do it as well, would it be better that they do it anyway and free me up to do more important things?

Having said this, I am slow learn and have become aware that there are some cautions needed in delegating. 

First, suppose I delegate to a person of lower "authority" than me, but who I have full confidence in. Others may not think they have the appropriate authority and so may be reluctant to act on or support what my delegate is.

Second, delegating tasks is no good if the person does not have the time, energy, and resources to complete the tasks. I may also need to provide the necessary resources and help them to see how they might delegate some tasks too.

3. Before embarking on a task, large or small, be clear on what your goal is.

This reduces the chance of getting distracted. Here is a concrete example. I often want to look for a paper on a specific question I have. Yet, I find that an hour later I am looking at my fourth paper because I got distracted by something I found interesting... and I have forgotten my initial question.

Some earlier thoughts on time management are here.

I welcome other suggestions.

Thursday, April 1, 2021

Where might condensed matter physics be heading?

Will there be big new discoveries? Will old problems be solved?  

I have finished my draft of, "An endless frontier" the last chapter of Condensed Matter Physics: A Very Short Introduction.

I aim to give a balanced perspective that is optimistic but realistic. Have I? Obviously, this is highly subjective.

I am interested in general feedback, particularly on whether your aunt or uncle or an eager undergraduate would find this interesting and engaging.

Besides your own research area :), are there particular topics that you think are ripe for exploration?

Perhaps, a cartoon about predicting the future. Maybe one of these two?