Featured Research

from universities, journals, and other organizations

Negative resistivity leads to positive resistance in the presence of a magnetic field

Date:
December 11, 2013
Source:
Georgia State University
Summary:
In the presence of a magnetic field, negative resistivity can produce a positive resistance, along with a sign reversal in the Hall effect, in GaAs/AlGaAs semiconductor devices.

In a paper appearing in Nature's Scientific Reports, Dr. Ramesh Mani, professor of physics and astronomy at Georgia State University, reports that, in the presence of a magnetic field, negative resistivity can produce a positive resistance, along with a sign reversal in the Hall effect, in GaAs/AlGaAs semiconductor devices.

The electrical resistance is a basic property of components known as resistors that occur in electrical circuits. Usually, the resistor serves to limit the electric current -- the flow of electrons -- to the desired value within the circuit in electronic applications. However, a large current through a resistor can also help to generate heat, and this principle is used in toasters, ovens, space heaters, and window defrosters. Resistors also occur in sensing applications as in strain gauges, gas sensors, etc., when the resistive element exhibits sensitivity to external stimuli. The resistance of a material depends upon the material property called the resistivity. The material resistivity generally takes on positive values, which indicates that electrical energy is dissipated within the material, when a current is passed through it.

In research that is supported by grants from the U.S. Department of Energy and the U.S. Army Research Office, Mani examined the relation between the resistivity and the resistance of microwave photo-excited, very thin sheets of electrons in the presence of a magnetic field with his colleague Annika Kriisa from Emory University.

The motivation for this work came from the fact that, over the past decade, theoretical physics has concerned itself with the remarkable possibility that the material resistivity can take on negative values in special systems, called two-dimensional electron gases (2DEG), at low temperatures in the presence of a magnetic field, when the 2DEG's are illuminated with microwaves -- the same type of microwaves that occur in microwave ovens. That is, scientists have suggested that cooking a 2DEG with microwaves in a magnetic field can help to produce negative resistivity. Yet, the consequences of a negative resistivity were not well understood. The work of Mani and Kriisa helps to clear up some mysteries.

The relation between the resistivity and the resistance is straightforward in the absence of a magnetic field: a positive resistivity will lead to a positive resistance and a negative resistivity will lead to a negative resistance. The application of a magnetic field generates something called a Hall effect in the sample that complicates the relation between the resistivity and the resistance at finite magnetic fields. The reason for the complication is that, in a small magnetic field, the Hall effect can be large compared to the resistive effect in very clean 2D electron systems. In such a situation, the Hall effect decides how the system is going to respond to the negative resistivity. This work by Mani and Kriisa shows that the 2D electron system can show a positive resistance in response to a negative resistivity as the Hall effect reverses its sign.

This result will help to further understand the proposed spectacular properties of systems exhibiting negative resistivity, as it also provides more insight into the intricacies of the Hall effect -- an effect discovered by the American scientist E. H. Hall circa 1879.


Story Source:

The above story is based on materials provided by Georgia State University. Note: Materials may be edited for content and length.


Journal Reference:

  1. R. G. Mani, A. Kriisa. Magneto-transport characteristics of a 2D electron system driven to negative magneto-conductivity by microwave photoexcitation. Scientific Reports, 2013; 3 DOI: 10.1038/srep03478

Cite This Page:

Georgia State University. "Negative resistivity leads to positive resistance in the presence of a magnetic field." ScienceDaily. ScienceDaily, 11 December 2013. <www.sciencedaily.com/releases/2013/12/131211131947.htm>.
Georgia State University. (2013, December 11). Negative resistivity leads to positive resistance in the presence of a magnetic field. ScienceDaily. Retrieved October 21, 2014 from www.sciencedaily.com/releases/2013/12/131211131947.htm
Georgia State University. "Negative resistivity leads to positive resistance in the presence of a magnetic field." ScienceDaily. www.sciencedaily.com/releases/2013/12/131211131947.htm (accessed October 21, 2014).

Share This



More Matter & Energy News

Tuesday, October 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Graphene Paint Offers Rust-Free Future

Graphene Paint Offers Rust-Free Future

Reuters - Innovations Video Online (Oct. 21, 2014) British scientists have developed a prototype graphene paint that can make coatings which are resistant to liquids, gases, and chemicals. The team says the paint could have a variety of uses, from stopping ships rusting to keeping food fresher for longer. Jim Drury reports. Video provided by Reuters
Powered by NewsLook.com
Gulfstream G500, G600 Unveiling

Gulfstream G500, G600 Unveiling

Flying (Oct. 20, 2014) Watch Gulfstream's public launch of the G500 and G600 at their headquarters in Savannah, Ga., along with a surprise unveiling of the G500, which taxied up under its own power. Video provided by Flying
Powered by NewsLook.com
Japanese Scientists Unveil Floating 3D Projection

Japanese Scientists Unveil Floating 3D Projection

Reuters - Innovations Video Online (Oct. 20, 2014) Scientists in Tokyo have demonstrated what they say is the world's first 3D projection that floats in mid air. A laser that fires a pulse up to a thousand times a second superheats molecules in the air, creating a spark which can be guided to certain points in the air to shape what the human eye perceives as an image. Matthew Stock reports. Video provided by Reuters
Powered by NewsLook.com
Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-Fuel Impala

3BL Media (Oct. 20, 2014) Hey, Doc! Sewage, Beer and Food Scraps Can Power Chevrolet’s Bi-fuel Impala Video provided by 3BL
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins