scattering and hall effect

1. Topic:
Umklapp Scattering , Hall Effect.
Presented To:
Dr. Kashif Ch
Presented By:
Usama Yousaf Butt
BS Phy (VIII)Eve
BSF1800372
University of Education , Township , Lahore.
Usama Yousaf

2. Usama Yousaf
Introduction
◾Basically , it is an inelastic scattering of photon
which results in the emission of phonon.
Let know about ‘’phonon’’ and ‘’photon’’.
◾A phonon is a collective excitation in a periodic
,elastic arrangement of atoms or molecules in
condensed matter , specially in solids and some liquids.
E= 𝔫ℏω
◾A photon is a tiny particle that comprises waves of
electromagnetic radiation. Photons have no charge, no
resting mass, and travel at the speed of light.

3. Usama Yousaf
:Umklapp Scattering:
The process which causes emission or absorption of phonon as a
result of in-elastic scattering.
Here , there are two cases , either there is emission or absorption .
First of all we discuss case one.
Consider a incident photon strikes on a crystal which creats
phonon and photon is scattered.

4. Usama Yousaf
From the conservation of wave vector;
Whereas for the conservation of momentum;
And for the conservation of energy;

5. Usama Yousaf
On the other hand in second case , when the photon strikes the
the crystal the phonon is absorbed and photon is scattered .
Conservation of wave vector ;
Conservation of momentum;
Conservation of energy;

6. Usama Yousaf
: Hall Effect :
The production of potential difference across an electrical conductor
when a magnetic field is applied perpendicular to the direction of
current .
When the magnetic field is applied perpendicular to the direction of
current then a transverse electric field is developed which is
perpendicular to both direction of current and magnetic field and
Called Hall field.

7. Usama Yousaf
: Expression of Hall Voltage:
Due to applied magnetic field , electrons tend to move in one
direction and there will be deficiency of electrons on other sides of
conductor, due to which potential difference is produced called
hall voltage .

8. Usama Yousaf
: Applications:
• Magnetic field sensing equipment
• For the measurement of direct current, Hall effect Tong
Tester is used.
• It is used in phase angle measurement
• Proximity detectors
• Hall effect Sensors and Probes
• Linear or Angular displacement transducers
• For detecting wheel speed and accordingly assist the anti-
lock braking system

9. Usama Yousaf