Condensed concepts

I have really enjoyed this week at the  Australasian Workshop on Emergent Quantum Matter.  My UQ colleague Matt Davis is to be congratulated for putting together an excellent program. There was nice balance of cold atom and solid state talks. Is there anything that stood out to me? Yes. Vortices, (Josephson) phase coherence, and dimensional crossovers. Vortices kept coming up and remain a fascinating and perplexing problem. Vortices are mesoscopic, intermediate between the microscopic (atomic) and macroscopic scales. The length scale associated with them is emergent. They have some quantum properties (quantised circulation) but obey classical equations of motion, but interact with microscopic degrees of freedom (quasi-particles and phonons). When one has a broken symmetry vortices are novel emergent low energy excitations. They are topological defects in the order parameter. Given how much they have been studied in superfluid 4He and superconductors one would think they were pre

I have been asked to speak at a grant writing workshop for the School of Mathematics and Physics at UQ. Here are a few preliminary thoughts. Consider not applying. Seriously. Consider the opportunity cost . An application requires a lot of time and energy. The chances of success are slim. Would you be better off spending the time writing a paper and waiting to apply next year? Or, would it be best to write one rather than two applications? You do have a choice. Don't listen to me. It is just one opinion. Some of my colleagues will give you the opposite advice. I have never been on a grant selection committee. My last 3 grant applications failed. Postmortems of failed applications are just speculation. What does and does not get funded remains a mystery to me. Take comfort from the "randomness" of the system. You have a chance. Don't stress the details. Recycle old unsuccessful applications. Don't take it personally when you fail. Who is your actual aud

Someone has to say it. I said it publicly today. Several people told me they were glad to hear it. Majorana fermions are fascinating from a fundamental science point of view. They are worth investigating by a few theoretical and experimental groups. However, they are the latest fashion that is taking the solid state and quantum information communities by storm. It is the latest exotica . Much of the justification for all this research investment is that Majorana fermions could be used for "fault tolerant" quantum computing. Lets get real.  Lets not kid ourselves. First, as far as I am aware, no one has even demonstrated yet that the relevant solid state "realisations" even exhibit Majorana statistics. Suppose they do. Maybe in a few years someone will have 2 qubits. Looking at the complicated nanoscale devices and fabrication needed I fail to see how on any reasonable time scale (decades?) one is going to produce say 6-8 qubits. Yet even that is just a quantum

Here are the slides for my talk, "An introduction to emergent quantum matter" that I am giving tomorrow at the  Australasian Workshop on Emergent Quantum Matter. A good discussion of some of the issues is Laughlin and Pines article  The Theory of Everything  and Piers Coleman 's article Many-body Physics: Unfinished Revolution. A more extensive and introductory discussion by Pines is at  Physics for the 21st Century. I welcome any comments.

I really enjoyed my visit to the TIFR Centre for Interdisciplinary Sciences (TCIS) of the Tata Institute for Fundamental Research in Hyderabad. This is an ambitious and exciting new venture. Higher education and basic research is expanding rapidly in India, with many new IITs, IISERs, and Central Universities. These are all hiring and so it is wonderful time to be looking for a science faculty job in India. The initial focus of hiring of the new campus of TIFR (India's premier research institution in Mumbai) has been on soft condensed matter (broadly defined) with connections in biology and chemistry. There are many good reasons for this focus. Foremost, is that there excellent Indian's working in this area. However, I see many other reasons why choosing this area is a much better idea than quantum condensed matter, ultra cold atoms, quantum information, cosmology, elementary particle physics, string theory (yuk!), ... Other reasons why I think investing in soft matter is

On monday I am giving the opening talk at the Australasian Workshop on Emergent Quantum Matter.  Since it is a broad audience with a range of backgrounds I am going to give a tutorial talk, building on the UQ colloquium I gave earlier this year.   Later I will post my draft slides. One concept I want to expand on is the concept of rigidity, associated with broken symmetry . To do this I am reading a nice article "Some general thoughts about broken symmetry," written by Phil Anderson in 1981. It is reprinted in A Career in Theoretical Physics , and here is a scanned copy  of the article. It contains the figure above. What is the connection between the "rigidity" of  solids and broken symmetry? A liquid is invariant under continuous translations and rotations. When it becomes a solid it is only invariant under discrete rotations and translations. Symmetry is broken. Unlike a liquid, a solid can "sustain/resist" a shear stress. Solids are rigid. I als

While in India, I enjoyed reading Chetan Bhagat 's best selling novel,  Five Point Someone:  What Not to do at IIT . The novel was made into a commercially successful movie, 3 idiots. The latter is only based loosely on the novel, and I think is better. I loved it. In the novel, the villainous Professor Cherian undergoes a transformation. At the end of the novel he departs from his usual graduation speech and says the following profound words.  Anyway, this is my message to all you students as you find your future. One, believe in yourself, and don’t let a GPA, performance review or promotion in a job define you . There is more to life than these things - your family, your friends, your internal desires and goals. And the grades you get in dealing with each of these areas will define you as a person.    Two, don’t judge others too quickly. I thought my son was useless because he didnt get into IIT. I tell you, I was a useless father. It is great to get into IIT, but it is

Very important. You will learn a lot from them. Recently, when I visited TIFR-Hyderabad I was asked to meet with a group of graduate students for a question and answer session on career issues. This was actually the first time I have actually done something like that. The students had many excellent questions. Some I may later blog about. Here I will just focus on this one question. Getting a Ph.D is not just about writing a thesis or even going to classes, doing experiments, talking to your advisor, and passing exams. At every stage of a program you can learn an immense amount from informal interactions with your peers [your class cohort]. Each has different background, interests, expertise, strengths, and weaknesses. Talking with them and sometimes working together on joint projects can be immensely valuable. Just the art of learning to talk to each other, asking questions , and crossing specialist boundaries [theory vs. experiment, chemistry vs. physics, field theory vs. conden

Yes! It is amazing how since the end of the cold war the issue of the nuclear weapons stockpiles of the USA and Russia attract little political attention and concern. In his usual inimitable style John Oliver highlights why we should be concerned.

Today I am visiting the Chemistry department at Hyderabad Central University. My host is Susanta Mahapatra. He has done some very nice work on non-adiabatic dynamics in the excited states of organic molecules. A nice review is here. Some of this work is relevant to the puzzle of diffuse interstellar bands and is described in this PRL. I am giving a talk "Effective Hamiltonians for excited states of fluorescent proteins and methine dyes". The slides are here.  A relevant paper with Seth Olsen is here.

Tomorrow I am giving a seminar at the Tata Institute for Fundamental Research (TIFR) Centre for Interdisciplinary Sciences in Hyderabad. Here is the current version of the slides, "Effect of quantum nuclear motion on hydrogen bonding." Most of the talk is based on this recent paper.

It is tempting to think that with advances in technology that we don’t really need  -live lectures and tutorials. Students can just watch videos of the worlds best lecturers at their convenience and in the comfort of their home. Tutorials can be done online, i.e. MOOCs.  -conferences. they can be done virtually with video conferencing. -for students doing non-experimental Ph.Ds to ever come on campus. -visits to collaborators. It can be done via email and Skype. This will save lots of money and time (and carbon footprint), particularly that associated with international travel. But, we should be nervous that the loudest proponents of these initiatives are mostly politicians, neoliberal “managers”, and commercial outfits, most of whom are not (and sometimes never have been) actual teachers or researchers. With regard to collaborations, I continue to be surprised at how effective personal visits and informal discussions are . Even when it is not clear to me that a face to f

Jure Kokalj and I just finished a paper Enhancement of the thermal expansion of organic charge transfer salts by strong electronic correlations Our main results concerning the electronic contribution to the thermal expansion alpha are as follows. (i) At low temperatures strong correlations can increase the thermal expansion by as much as an order of magnitude. (ii) A non-monotonic temperature dependence of alpha is possible. (iii) Significant orientational dependence is possible, including the expansion having the opposite sign in different directions. (iv) In the metallic phase the crossover from a Fermi liquid to a bad metal may be reflected in a maximum in the temperature dependence of alpha. (v) In the Mott insulating phase a maximum in the temperature dependence of alpha can occur, at a temperature comparable to that at which a maximum also occurs in the specific heat and the magnetic susceptibility. (vi) All of the above results are sensitive to the proximity to th

Previously I posted about the role of short strong H-bonds [sometimes called low-barrier H-bonds] in the enzyme KSI. There is a very interesting paper Using Unnatural Amino Acids to Probe the Energetics of Oxyanion Hole Hydrogen Bonds in the Ketosteroid Isomerase Active Site Aditya Natarajan, Jason P. Schwans, and Daniel Herschlag The authors report a beautifully designed and implemented experiment. The idea and results are elegantly summarised in the graphical abstract below.  The key Tyrosine amino acid (Tyr16) is substituted with different fluorinated versions. These have different proton affinities (acidity or pKa) to the native amino acid. It is well established that the strength of a hydrogen bond is maximal when the hydrogen donor and acceptor have the same proton affinity [pKa matching].  This can be naturally understood in terms of a diabatic state model for H-bonding . The aim of the experiment is to vary the strength of one of the key hydrogen bonds in the

It continues to amaze and frustrate me how some people will do the following. Take experimental data for a specific quantity [e.g. resistivity vs. temperature]. Fit the data to a function from some exotic theory X involving N free parameters. Claim that the "successful" fit "proves" that X is the correct theory. Why am I skeptical? What would it take to convince me X is actually valid? 1. Have N < 4, remembering the elephants wiggling trunk. 2. With the same set of parameters also fit at least one, and preferably several,  other experimental observation [e.g. thermopower vs. temperature]. 3. Show that the fit parameters are physically reasonable and consistent with estimates from independent determinations. Science is all about comparisons. 4. Also fit the data to the predictions of mundane theory M, and alternative exotic theory X2, and clearly show they cannot fit the data. i.e., apply the method of multiple alternative hypotheses. Finally, there is