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APS 2010 March Meeting: March 2010: Monthly Archives

APS 2010 March Meeting: March 2010 Archives

And the winner is…David Singh

By Hamish Johnston

My colleague Sharice Collins has just posted a large number of photos from IOP Publishing’s glitzy reception held on 17 March at the APS March Meeting in Portland.

As I mentioned in a previous blog entry, this year’s party celebrated the twentieth anniversary of our journal Nanotechnology.

The party included a draw for an iPod Nano, which was won by David Singh of ORNL.

Thanks to Sharice for an excellent bash – and you can see in the bottom centre photo that, despite all the hard work, she still enjoyed herself.

Nanotechnology keeps on growing

By Hamish Johnston in Portland, Oregon

The hottest party in town last night was the Institute of Physics Publishing reception at the Hilton Hotel. This year we are celebrating the 20th anniversary of our journal Nanotechnology and group publisher Nina Couzin gave a nice talk on the history of the journal and plans for the future.

Late last year, a special issue was published to commemorate the 20th volume of the journal. Many of the papers are free, so make sure you have a good browse of the content.

And no mention of nanotechnology is complete without a nod to, where you will find the latest research news.

The reception is a great way to gauge what’s hot and what’s not. After three days of sessions, folks were still very keen on topological insulators. But the session that everyone was talking about was Eugenie Samuel Reich’s talk about the “Schoen affair”.

Sadly, I missed her talk because I had already read her article on the scientific fraudster, which appeared in Physics World last year – an electronic version is available to IOP members only.

The most interesting conversation I had was with a theorist who recently shifted his research interests from high-Tc superconductors to topological insulators and graphene. Why? It was the look of horror on potential graduate students’ faces when he started to explain what he did!

Nathan’s results table

By Hamish Johnston in Portland, Oregon

Although college basketball’s “March madness” is about to start, it’s the physics of baseball that people are talking about here at the APS March Meeting.

Alan Nathan of the University of Illinois at Urbana Champaign spoke about his analysis of data from the PITCHf/x and HITf/x systems that have been installed in all major-league ballparks by Sport Vision.

These systems track the speed and trajectory of the ball allowing, for example, digital reconstructions of plays for television viewers.

It turns out that all of these data are available to the public – and Nathan has used them to study the flight of the baseball.

One question he addressed is the widely held belief that hit balls travel further in the new Yankee Stadium in New York than in other ballparks.

Nathan defined the “carry” of a hit as the distance the ball actually travelled divided by the distance the ball would have travelled (given its velocity when hit) in a vacuum.

You can see the results above, and there is nothing special about the new Yankee Stadium – denoted “NYC-A” – indeed its carry is a little below average (the red line).

So what’s the story with Denver?

Here’s a hint – Denver’s Colorado Rockies used to play in Mile High Stadium.

Nan Haemer sings Updike

By Hamish Johnston in Portland, Oregon

My fondest memory of the 2010 APS March Meeting will be the soprano Nan Haemer’s performance of Updike’s Science – music by the physicist Brian Holmes and words by the late John Updike.

Brian is at the left of the photograph above, turning pages for Terry Nelson on the piano.

As well as being a condensed matter physicist at San Jose State University, Holmes is a professional French horn player and a composer.

Updike’s Science consists of musical settings of six poems by John Updike. Some of the poems make direct reference to science – “Cosmic gall”, for example, begins:

“Neutrinos they are very small…”

Other poems are included because they remind Holmes of science – “Lament for cocoa”, for example could be a lament for thermodynamics with the lines:

“The scum has come, My cocoa’s cold”

Holmes blowing his horn

Before the performance Holmes entertained the crowd with a lively demonstration of the physics of brass instruments.

What did I learn? Well it seems that the pitch of a trumpet with a bell is higher than a similar instrument that ends in a plain tube. Although Holmes didn’t say so, the logical conclusion is that the bigger the bell the higher the pitch – but I would have thought bigger bells result in lower pitches.

The reason, I think, is that a larger bell means that the acoustic node of the instrument is further into the trumpet – which shortens the wavelength of the sound, boosting the pitch.

Heads in the clouds

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Fluffy simulations

By Hamish Johnston in Portland, Oregon

Have you ever wondered why clouds are fluffy?

Well, it’s not an easy question – according to Yong Wang at UCLA. Wang was here at the APS March Meeting to talk about his simulations of cumulus clouds, the fluffy ones that tend to appear after about noon on a sunny day and don’t tend to spoil the rest of the day.

Wang says that these clouds are droplets supported by thermal convection, and their shapes arise because this is a “complex non-linear system” that is driven by thermal plumes.

The simulation begins with a homogeneous layer of water droplets into which small thermal plumes rise. After a while, the jostled droplets look a lot like fluffy cumulus clouds (see above).

Wang didn’t seem to think that there were any practical applications for his work – but I would have thought this could help climate physicists understand why certain clouds form.

You can read more about Wang’s simulations here.

Record breaking accelerator

By Hamish Johnston in Portland, Oregon

Here’s a question for you, what is the most powerful accelerator in the world?

No, it’s not the LHC – that holds the record for energy – the answer is the Spallation Neutron Source (SNS) at the Oak National Lab in Tennessee.

In September 2009 the facility delivered a pulsed beam of 1 GeV protons at a power of 1 MW.

The pulses are fired at a target of liquid mercury, creating copious amounts of neutrons, which can then be slowed down and used for studying solids and liquids.

This afternoon I saw a nice talk by Stuart Henderson of Oak Ridge about recent progress at the SNS. Since experiments began in 2006, the number of instruments attached to the neutron beamline has grown to 12 and he expects that 16 instruments will be running by 2012.

And of course, Oak Ridge hope to upgrade the facility between 2012–2017 – boosting the energy to 1.3 GeV and the power to 3 MW.

Rising plumes

By Hamish Johnston in Portland, Oregon

Any guesses as to what you are looking at?

The red shape is a “person” sitting in a small room. The temperature at the surface of the person is 25 degrees – the temperature of your clothes, apparently – and the temperature of the room is 20 degrees.

The image is from a huge simulation of how air circulates in a room with floor and ceiling vents that was done by John McLaughlin and colleagues at Clarkson University.

The yellow plumes are warm air rising from the sitting person – and McLaughlin looked at how tiny particles comparable to viruses or pollen behaved in the room. He found that the plumes tend to concentrate the particles over the person’s head – and then they fall down onto the poor person!

This could be bad news in a hospital, for example, where there could be lots of nasty bugs floating around.

So if your head is getting dusty, perhaps it’s because you are sitting perfectly still in a small room.

Packed house for Andre Geim
By Hamish Johnston in Portland, Oregon

I had to push my way through the crowd here at the APS March Meeting just to stand at the back of Andre Geim’s talk called “Graphene update”. It seems that there is a still a lot of interest in the wonder material – sheets of carbon just one atom thick – that promises to revolutionize electronics.

The University of Manchester-based graphene guru spoke about a half-dozen or so open questions in the field.

Is graphene ferromagnetic at room temperature, as some have claimed?

“No,” says Geim, who explained how he and his colleagues found no evidence for ferromagnetism down to a chilly 2K.

And what about the vexing question of how to create a bandgap in gapless graphene so that it can be used to create conventional semiconductor devices?

Straining graphene by up to 10% hasn’t worked – and recent calculations suggest that you would have to have to strain the stuff by as much as 25% before a gap appears.

One way forward, according to Geim, is to somehow apply just the right amount of “non-uniform” strain to the material. While this appears to work in theory, it requires the strain to vary on length scales of about a micron – which physicists can’t do today.

A gap could also be introduced by altering the chemistry of graphene. Geim and colleagues have already hydrogenated graphene to create graphane – which has a gap. However, Geim says the material is “unstable” and not suitable for making semiconductor devices.

So if hydrogen doesn’t work, why not try fluorine to create fluorographene? That’s what Geim and colleagues have done – and although the result was a semiconductor with a great deal of disorder, he said that fluorographene could be the way forward to a gap.

Perhaps the most intriguing topic touched on by Geim is the fabrication of “quantum capacitors”, which comprise one graphene plate and one metal plate. In such a device the capacitance is a function of the applied voltage, dipping to zero at zero voltage. And the capacitance oscillates if a magnetic field is applied. I’m not sure what you could do with such a device – but it’s yet another example of the wonders of graphene.

By Hamish Johnston in Portland, Oregon

I know it’s a cliché, but the quantum world gets weirder the more you learn about how it works.

Yesterday I went to a talk by Graeme Smith of IBM Research, whose talk was entitled “Surprises in the theory of quantum communications”.

The surprise that Smith focused on is that two transmission channels – both of which are too noisy or lossy to transmit quantum information individually – can somehow join forces to create a very good channel for transmitting quantum information.

A classical transmission channel fails if you put a signal in one end and get nothing (or just noise) out the other end. By contrast, a quantum channel can fail if you input quantum information but its quantum nature is lost when it gets to the other end – information is transferred, but not quantum information.

But according to Smith, it’s possible that each channel is capable of transmitting a certain subset of the quantum information – but not all of it. The trick is to have two or more channels combine their quantum strengths to overcome their weaknesses.

“The weakness of one is made up for by the strength of the other,” explained Smith.

While it sounds like a great way to build a robust transmission channel from a bunch of bad connections, Smith said that it is not currently clear how to decide which bad channels can be grouped together to create a good channel.

It’s a whopper

By Hamish Johnston in Portland, Oregon

Swinging above the heads of thousands of physicists as they rush to the next session is a very large Foucault pendulum. Indeed, Wikipedia suggests that it is the world’s largest.

It’s day two here at the APS March Meeting and I’m off to hear about how electric and magnetic fields can be synthesized for ultracold neutral atoms.

Steal a speaker’s data at your peril

By Hamish Johnston in Portland Oregon

I couldn’t resist taking a cheeky snap of this sign in a corridor of the convention centre.

Is this a response to the infamous “physics paparazzi”, who take photos of other people’s data during talks and then go off and write a paper that beats the original researchers into publication?

You may recall the scandal surrounding PAMELA data a few years ago when that very thing happened.

When I asked in the press room I was assured that reputable members of the media such as myself were free to take photos – and a press officer is looking into whether there is a ban on delegates taking photos.

As I only saw one sign in the giant convention centre, a more plausible explanation is that the sign was left over from last week’s event.

Zhang (left) next to Molenkamp
By Hamish Johnston in Portland, Oregon

There was a slight panic here in the press room over lunch when we all realized that we will soon be writing about topological insulators. We weren’t exactly sure what they were – but it’s becoming clear that topological insulators are the hot topic here at the APS March Meeting.

Fortunately we received a good introduction by some of the leading lights in the field, including Shou-Cheng Zhang of Stanford University. Zhang described topological insulators as “a new state of matter that has been predicted and discovered”. The prediction – by Zhang, I believe – occurred in 2006 and the first material was made a year later by Laurens Molenkamp at the University of W├╝rzburg, who was also at the press conference.

Topological insulators are actually pretty good conductors (more on that later) and could lead to smaller integrated circuits that run faster and cooler. There is even the suggestion that axions and Majorana fermions could be lurking in these materials.

A simple description of a topological insulator is a material that is an insulator in the bulk, but a very good conductor on the surface.

Why? Well, it seems to have something to do with the quantum spin Hall effect – the accumulation of electrons with opposite spins on opposite sides of a conductor.

Let’s say a spin-up electron is flowing along the surface and scatters off an impurity.
The scattering process involves orbital angular momentum – and thanks to spin-orbit coupling, the spin of the electron is also rotated during the scattering.

Here’s the tricky bit that I didn’t quite understand. If the electron is scattered backwards the spin rotation introduces a phase shift of –1. If you think of this scattering as wave diffraction, destructive interference means that the electron can’t propagate in the opposite direction.

No backscattering means that the resistance of the material is very low, which is very useful if you are trying to make very tiny electronic circuits.

Sounds reasonable, but there are a few things I don’t understand. For one thing, this explanation seems to hinge on the electron only being able to scatter forwards or backwards – but not off to the side.

I’d better start reading-up on topological insulators.

mount hood.jpg
Mount Hood in the distance

By Hamish Johnston in Portland, Oregon

I arrived here in Portland on Friday evening and spent the weekend sightseeing with my brother.

Spring also arrived here in the Pacific Northwest, with the daffodils up and the cherry trees in full bloom – the sort of March we’ve come to expect in England, but not this year.

City of bridges

While it’s warm, it’s not warm enough to melt the snow on Mount Hood, which I can see from my hotel window – at least I think that is Mount Hood.

This morning I took the tram over one of Portland’s many bridges to the twin crystal towers of the convention centre for day one of the American Physical Society March Meeting – a solid week of solid-state physics.

I have sat in on two press conferences so far, one on topological insulators and the other on the physics of catastrophes. More on both later…it’s time for lunch in the pressroom.

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