Thursday, December 5, 2024, 3:45 – 4:45pm

Cascade of new even-denominator fractional quantum Hall states

One of the most remarkable phenomena in physics arises when two-dimensional electrons are subjected to a strong magnetic field: they exhibit a myriad of fractional quantum Hall states, each marked by a quantized Hall resistance given by (h/e2)/f, where f is a fraction. Arising from an interplay between topology and interaction, these have given rise to an amazing body of new concepts. A large majority of fractions have odd denominators and are understood in terms of integer quantum Hall effect of particles called composite fermions. The excitations of these states are neither fermions nor bosons but are “anyons.” The even-denominator states are predicted to produce even more complex excitations, anyons that obey “non-Abelian” statistics. These fascinating excitations possess non-trivial braiding properties and have been advanced as a potential platform for fault-tolerant topological quantum computing. Until recently, even-denominator fractional quantum Hall states had been rare, essentially observed for f = 5/2 and its analogs in bilayer graphene, and f = ½ in wide quantum wells. I will show that our new ultrahigh-quality GaAs/AlAs samples, which are some of the purest solid-state materials (residual impurity concentration well below 1 per 10 billion atoms), reveal new even-denominator states at ¼, ¾, 3/8, 3/10,1/6 and 1/8, thereby tremendously enriching the fractional quantum Hall physics and expanding the reach of non-Abelian statistics. These developments also highlight how progress in physics is intimately connected to our ability to grow high quality materials.

Based on work done in collaboration with Chengyu Wang, Adbhut Gupta, Pranav Thekke Madathil, Siddharth K. Singh, Casey Calhoun, Chia-Tse Tai, Yoon Jang (Edwin) Chung, Md. Shafayat Hossain, Meng K. Ma, Roland Winkler, Ken West, Kirk Baldwin, and Loren Pfeiffer.

Event Name: Physics Colloquium 2024 Mansour Shayegan
Organization: UP – Dept – PHYS
Event Image’s Description (Alt Text): Mansour Shayegan
Event/Venue Link (Map URL or Virtual Event Link): map.psu.edu…
Location Details (Venue Name/Virtual Platform): 119 Osmond Laboratory
Event Locator: 2024-ANAABH