Heat Transport Studies Provide Evidence for a New Phase of Matter

July 11, 2018

Figure 1*: A recent thermal transport study of gallium arsenide quantum wells measured a fractional thermal Hall conductivity, which is consistent with the emergence of a non-Abelian phase called the PH-Pfaffian. Two new theoretical works have shown that this phase could arise from hybridization among two other phases, the Pfaffian and anti-Pfaffian, arranged in a quilt-like pattern. Between patches of the two phases are edge states that carry heat but not electric charge. [Credit: APS/Carin Cain]

Around 40 years ago, physicists stumbled on an elegant recipe for creating exotic phases of matter: Pour electrons into a clean two-dimensional environment, add a magnetic field, and allow to cool. Out comes a dazzling variety of so-called fractional quantum Hall phases. Certain types of fractional quantum Hall phases, called non-Abelian, provide a potential platform for intrinsically error-resistant quantum computation. However, unambiguously identifying these phases poses a notorious challenge for experimentalists, as measurements often do not uniquely pinpoint which of several candidate phases is present.

Experiments published last month provide direct evidence that a previously studied quantum Hall phase first observed long ago is indeed non-Abelian. In a delightful surprise, the observations appear to rule out the two leading candidate phases that were expected from theory! Now David Mross and colleagues from the Weizmann Institute of Science in Israel and Chong Wang and colleagues from Harvard University describe a possible resolution: Because of disorder, the system might harbor patches of each of the two theoretically expected candidates, which combine to form a distinct non-Abelian phase compatible with observations...

* Continue reading "Viewpoint: A Hot Topic in the Quantum Hall Effect" by Jason Alicea, Physics 11, July 9, 2018. https://physics.aps.org/articles/v11/70

Also read the original paper by Chong Wang, Ashvin Vishwanath, and Bertrand I. Halperin, "Topological order from disorder and the quantized Hall thermal metal: Possible applications to the ν=5/2 state," Phys. Rev. B 98, 045112 (2018). https://doi.org/10.1103/PhysRevB.98.045112