Related Experiment Video
Updated: Jun 23, 2026
10:36
Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials
Published on: January 21, 2016
Optical absorption to probe the quantum Hall ferromagnet at filling factor nu=1
P Plochocka1, J M Schneider, D K Maude
1Laboratoire National des Champs Magnétiques Intenses, Grenoble High Magnetic Field Laboratory, 38042 Grenoble, France. Paulina.Plochocka@grenoble.cnrs.fr
Physical Review Letters
|April 28, 2009
Summary
Spin polarization in quantum Hall effects is fragile. The itinerant quantum Hall ferromagnet at filling factor nu=1 only shows full spin polarization at low temperatures and is sensitive to small changes in filling factor.
Area of Science:
- Condensed matter physics
- Quantum Hall effect studies
Background:
- The quantum Hall effect (QHE) exhibits unique electronic properties in two-dimensional electron systems under strong magnetic fields.
- Investigating spin polarization is crucial for understanding the underlying physics of QHE regimes, including integer and fractional states.
Purpose of the Study:
- To probe the spin polarization within the integer and fractional quantum Hall effect regimes using optical absorption measurements.
- To determine the conditions under which the system achieves full spin polarization and assess the stability of the quantum Hall ferromagnet at nu=1.
Main Methods:
- Utilized optical absorption spectroscopy to measure spin polarization.
- Systematically varied the filling factor (nu) and temperature to observe changes in spin polarization.
Main Results:
- Full spin polarization was observed exclusively at filling factor nu=1 and at extremely low temperatures (approximately 40 mK).
- Even minor alterations in the filling factor (delta nu approximately +/-0.01) induced significant depolarization.
- The quantum Hall ferromagnet at nu=1 demonstrated unexpected fragility towards temperature increases and small variations in filling factor.
Conclusions:
- The itinerant quantum Hall ferromagnet at nu=1 is surprisingly fragile.
- Both increasing temperature and small changes in filling factor can disrupt the spin polarization, highlighting the delicate nature of this magnetic state.
Related Concept Videos
01:30The Hall Effect
Edwin H. Hall, in the year 1879, devised an experiment that could be used to identify the polarity of the predominant charge carriers in a conducting material. From a historical perspective, this experiment was the first to demonstrate that the charge carriers in most metals are negative.
01:31Ferromagnetism
Materials like iron, nickel, and cobalt consist of magnetic domains, within which the magnetic dipoles are arranged parallel to each other. The magnetic dipoles are rigidly aligned in the same direction within a domain by quantum mechanical coupling among the atoms. This coupling is so strong that even thermal agitation at room temperature cannot break it. The result is that each domain has a net dipole moment. However, some materials have weaker coupling, and are ferromagnetic at lower...
01:02¹H NMR: Interpreting Distorted and Overlapping Signals
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...