Quantum Transport Research Lab

	Quantum Transport Research Lab
< Research >
>> Home	Magnetotransport in Two Dimensional Electron/Hole System (Dai)
>> People	The material in our experiment is compound semiconductor, such as, GaAs and InGaAs, two dimensional electron gas (2DEG) is confined inside the quantum well and random distributed in a plane
>> Research	FIG.1 a) structure of InGaAs/InAlAs/InGaAs b) band structure c) quantum well and one side Si+ doping layer
>> Publications
>> Links


	The density of state of 2DEG is uniform to different energy which is different from one dimensional electron gas (1DEG) and three dimensional electron gas(3DEG). But when the sample in a perpendicular magnetic field, all the electrons in the plane start cyclotron motion which causes the density of state discrete.(FIG2.) and occupied energy level become not continue anymore and landau level appear.
	FIG2 first one is density of state without magnetic filed second one (a,b,c included) is with magetic filed.
	Landau level is,. So the energy space between each level is . In room temperature, the exciting energy. Landau level cannot be observed. Only when in very low temperature,. landau level becomes well resolvable. So usually we run experiment in 0.3 K in a top loading He-3 refrigerate. (FIG3 ). The magnetic field is from a superconducting magnet.


	FIG3.top loading He-3 refrigerate
	FIG3.top loading He-3 refrigerate
	Integral quantum Hall Effect is usually found in hall trace magentotransport experiment. (FIG4). See integral quantum hall effect link
	FIG4 Magnetotransport result , Rxy is hall trace, integral quantum hall effect clearly show. Rxx is magneto resistance.	Spin effect sometimes also involved in magnetotransport. Rashba effect is one kind (FIG.5) In the asymmetric quantum well. , there is an electric field perpendicular to layers and it transforms into magnetic field in the rest frame of an electron moving along the layer. And this magnetic field leads to spin splitting. So without external magnetic fields, we also see spin splitting effect and this is the Rashba effect.
	FIG.5 illustration of Rashba effect
	For some semiconductor ,the carrier is holes. Two dimensional holes gas (2DHG) has it unique band structure. Unlike electrons, only single conduction band is available, holes have three subband in valence band: two heavy hole band , one light hole band. With the magnetic filed change ,its band structure change as well. So, the property of the 2DHG become more complicated. Recently, we are looking in the current induced magento transport of hole carrers and find the similar peak to zener tunneling in electrons system [1]. More results will be present for this special topic.

	[1] Yang et al. Phys. Rev. Lett. 89, 076801 (2002)



Dr. Rui-Rui Du rrd@rice.edu Rice University Physics & Astronomy Dell Butcher Hall Rm. 170 1900 Rice Blvd. Ent. 20 Houston, TX 77005 >Office Phone: 1-713-348-5780 >Lab Phone/Fax: 1-713-348-5719




Rice Physics & Astronomy

	Page Last Updated 1-21-09 by Kristjan Stone