Energy, Momentum, and Spin-resolved tunneling spectra of quantum Hall systems

Tunneling spectroscopy has an unique power in probing strong electronic correlations of many-body states in a solid. Here, we introduce a novel contactless pulsed tunneling technique that can visualize the energy, momentum, and spin-resolved electronic structure of a quantum Hall effect system. Unlike conventional planar tunneling that requires in-plane conductivity of the system, the pulsed tunneling method functions on strongly insulating systems at exact integer or fractional quantum Hall states. Furthermore, through use of pulses that drive tunneling in the extremely short time intervals, the technique eliminates perturbations such as heating effects or photo-excited defects that commonly occur in other methods. Using the pulsed tunneling technique, we visualize the evolution of discrete quantization of energy levels as well as the effect of electron-optic phonon interactions in energy-momentum space [1]. In addition to momentum and energy resolution, we performed spin-resolved tunneling that probes the ground-state spin polarization of the fractional quantum Hall states in a wide range of magnetic fields and filling factors. Moreover, we can detect the spin-dependent high energy states arising from the strong pair interactions. From these high energy features, we measure Haldane’s pseudopotentials that enabled us to directly determine the stability of the composite Fermi sea in a half-filled Landau level. These results illustrate the potentially broad applicability of the pulsed tunneling technique for studying the correlated electronic phases in a variety of two-dimensional materials.

[1] J. Jang, H.M. Yoo, L.N. Pfeiffer, K.W. West, K.W. Baldwin, and R.C. Ashoori, Science, 358, 901 (2017)