'Phonon Hall Effect' Observed

Oct 23, 2005 feature

What effect do magnetic fields have on uncharged particles?
Their effect on charged particles is familiar to every student of physics or electrical engineering. A common example is the Hall Effect, a basic phenomenon of solid state physics. This effect arises in current carrying materials when a magnetic field is applied perpendicular to the current flow.

The Lorentz force of electromagnetism acts perpendicularly to both the current and the magnetic field, establishing a voltage gradient in the material. Intuitively, one would not expect an analogous effect on uncharged particles, which do not couple to magnetic fields though obvious mechanisms like the Lorentz force. Yet in the October 7th issue of Physical Review Letters, French physicists report such an effect with phonons, uncharged units of mechanical excitation in solids. The group dubbed their finding the “phonon hall effect.”

The observed phenomenon is simple to describe. The experimenters induce a thermal current in a small crystal block by clamping two ends of the block with two heaters at different temperatures. They then apply a magnetic field to the material perpendicular to the thermal gradient. Under these conditions the group observed a temperature difference in the material perpendicular to both the original thermal current and the magnetic field. This temperature difference is the phonon hall effect.

The group performed their experiments using crystals of paramagnetic terbium gallium garnet (TGG). TGG makes an ideal material for these experiments because it contains strongly charged ions and large magnetic moments which allow it to strongly couple to magnetic fields. In addition, the material is dielectric, which prevents the phonon hall effect from being overshadowed by other solid state phenomena such as the Righi-Leduc effect. The authors claim that no microscopic theory yet exists to explain the phonon hall effect, although they present a series of macroscopic arguments justifying its existence. This study thus adds another mysterious phenomenon to the rich world of solid state physics.

by Joseph Levine, Copyright 2005 PhysOrg.com

Righi-Leduc Effect

Righi-Leduc Effect is a temperature gradient in the x direction that gives rise to a heat flow in the y direction and vice versa.

This is the thermal analogon to the Hall Effect, which arises if electric conduction is studied in a magnetic field.

Copyright Wikipedia, licensed under the GNU Free Documentation License.

Explore further: A 'quantum leap' in encryption technology

add to favorites email to friend print save as pdf

Related Stories

Relativity shakes a magnet

Mar 03, 2014

The research group of Professor Jairo Sinova at the Institute of Physics at Johannes Gutenberg University Mainz (JGU), in collaboration with researchers from Prague, Cambridge, and Nottingham, have predicted ...

Recommended for you

A 'quantum leap' in encryption technology

10 hours ago

Toshiba Research Europe, BT, ADVA Optical Networking and the National Physical Laboratory (NPL), the UK's National Measurement Institute, today announced the first successful trial of Quantum Key Distribution ...

Using antineutrinos to monitor nuclear reactors

10 hours ago

When monitoring nuclear reactors, the International Atomic Energy Agency has to rely on input given by the operators. In the future, antineutrino detectors may provide an additional option for monitoring. ...

Bake your own droplet lens

11 hours ago

A droplet of clear liquid can bend light, acting as a lens. Now, by exploiting this well-known phenomenon, researchers have developed a new process to create inexpensive high quality lenses that will cost ...

How do liquid foams block sound?

12 hours ago

Liquid foams have a remarkable property: they completely block the transmission of sound over a wide range of frequencies. CNRS physicists working in collaboration with teams from Paris Diderot and Rennes ...

Probing the sound of a quantum dot

13 hours ago

(Phys.org) —Physicists at the University of Sydney have discovered a method of using microwaves to probe the sounds of a quantum dot, a promising platform for building a quantum computer.

User comments : 0

More news stories

Phase transiting to a new quantum universe

(Phys.org) —Recent insight and discovery of a new class of quantum transition opens the way for a whole new subfield of materials physics and quantum technologies.

When things get glassy, molecules go fractal

Colorful church windows, beads on a necklace and many of our favorite plastics share something in common—they all belong to a state of matter known as glasses. School children learn the difference between ...

A 'quantum leap' in encryption technology

Toshiba Research Europe, BT, ADVA Optical Networking and the National Physical Laboratory (NPL), the UK's National Measurement Institute, today announced the first successful trial of Quantum Key Distribution ...

Genetic code of the deadly tsetse fly unraveled

Mining the genome of the disease-transmitting tsetse fly, researchers have revealed the genetic adaptions that allow it to have such unique biology and transmit disease to both humans and animals.