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A transport study of two-dimensional (2D) holes confined to wide GaAs quantum wells provides a glimpse of a subtle competition between different many-body phases at Landau level filling $\nu=3/2$ in tilted magnetic fields. At large tilt…

Mesoscale and Nanoscale Physics · Physics 2016-11-08 Yang Liu , M. A. Mueed , Md. Shafayat Hossain , S. Hasdermir , L. N. Pfeiffer , K. W. West , K. W. Baldwin , M. Shayegan

In a low-disorder two-dimensional electron system, when two Landau levels of opposite spin or pseudospin cross at the Fermi level, the dominance of the exchange energy can lead to a ferromagnetic, quantum Hall ground state whose gap is…

Mesoscale and Nanoscale Physics · Physics 2022-11-10 Meng K. Ma , Chengyu Wang , Y. J. Chung , L. N. Pfeiffer , K. W. West , K. W. Baldwin , R. Winkler , M. Shayegan

Using symmetry breaking strain to tune the valley occupation of a two-dimensional (2D) electron system in an AlAs quantum well, together with an applied in-plane magnetic field to tune the spin polarization, we independently control the…

Strongly Correlated Electrons · Physics 2014-02-03 O. Gunawan , T. Gokmen , K. Vakili , M. Padmanabhan , E. P. De Poortere , M. Shayegan

We use low temperature near-field optical spectroscopy to image the electron density distribution in the plane of a high mobility GaAs quantum well. We find that the electrons are not randomly distributed in the plane, but rather form…

Mesoscale and Nanoscale Physics · Physics 2009-11-07 Y. Yayon , M. Rappaport , V. Umansky , I. Bar-Joseph

In high-quality two-dimensional electrons confined to GaAs quantum wells, near Landau level filling factors $\nu=$ 1/2 and 1/4, we observe signatures of the commensurability of the electron-flux composite fermion cyclotron orbits with a…

Mesoscale and Nanoscale Physics · Physics 2015-06-16 D. Kamburov , M. A. Mueed , M. Shayegan , L. N. Pfeiffer , K. W. West , K. W. Baldwin , J. J. D. Lee , R. Winkler

In half-filled high Landau levels, two-dimensional electron systems possess collective phases which exhibit a strongly anisotropic resistivity tensor. A weak, but as yet unknown, rotational symmetry-breaking potential native to the host…

Mesoscale and Nanoscale Physics · Physics 2009-11-10 K. B. Cooper , J. P. Eisenstein , L. N. Pfeiffer , K. W. West

Nanowire double quantum dots occupied by an even number of electrons are investigated in the context of energy level structure revealed by electric dipole spin resonance measurements. We use numerically exact configuration interaction…

Mesoscale and Nanoscale Physics · Physics 2015-03-05 M. P. Nowak , B. Szafran

We propose two possible quantum microscopic mechanisms for intervalley transitions just at the Franck-Condon state in GaAs. The first is the simultaneously combined coulombic elastic transitions of two electrons,from the originally…

Materials Science · Physics 2015-12-18 Hiromasa Ohnishi , Norikazu Tomita , Keiichiro Nasu

We report heavy electron behavior in unconventional superconductor YFe$_2$Ge$_2$ ($T_C \,{=}\, 1.2$ K). We directly observe very heavy bands ($m_\mathrm{eff}\sim 25 m_e$) within $\sim$10 meV of the Fermi level $E_{F}$ using angle-resolved…

The electronic structure of InAs/AlSb/GaSb quantum wells embedded in AlSb barriers and in the presence of a perpendicular magnetic field is studied theoretically within the $14$-band ${\bf k}\cdot{\bf p}$ approach without making the axial…

Materials Science · Physics 2015-09-30 X. G. Wu , M. Pang

We report in this letter experimental results that confirm the two-dimensional nature of the electron systems in monolayer InN quantum wells embedded in GaN barriers. The electron density and mobility of the two-dimensional electron system…

Mesoscale and Nanoscale Physics · Physics 2015-06-22 W. Pan , E. Dimakis , G. T. Wang , T. D. Moustakas , D. C. Tsui

Electrons are offered a valley degree of freedom in presence of particular lattice structures. Manipulating valley degeneracy is the subject matter of an emerging field of investigation, mostly focused on charge transport in graphene. In…

Strongly Correlated Electrons · Physics 2012-04-18 Zengwei Zhu , Aurelie Collaudin , Benoit Fauque , Woun Kang , Kamran Behnia

We study two interacting electrons in a two-dimensional system under a strong magnetic field and show that their numerically exact solutions organize into a set of {\em sub-Landau levels} characterized by relative angular momentum quantum…

Strongly Correlated Electrons · Physics 2026-04-07 Guo-Qiang Hai

We have studied the optical and electrical spectra from an n i p LED as a function of magnetic field. This sample incorporated three GaAs quantum wells in the intrinsic region. This device had excess n type doping and as a result. The…

Mesoscale and Nanoscale Physics · Physics 2021-01-05 Imran Khan , Bipin Singh Koranga , Sunil Kumar

We report low-field magnetotransport data in two-dimensional hole systems in GaAs/AlGaAs heterostructures and quantum wells, in a large density range, $2.5 \times 10^{10} \leq p \leq 4.0 \times 10^{11}$ cm$^{-2}$, with primary focus on…

Mesoscale and Nanoscale Physics · Physics 2009-11-07 S. J. Papadakis , E. P. De Poortere , H. C. Manoharan , J. B. Yau , M. Shayegan , S. A. Lyon

We propose a model intended to qualitatively capture the electron-electron interaction physics of two-dimensional electron gases formed near transition-metal oxide heterojunctions containing $t_{2g}$ electrons with a density much smaller…

Strongly Correlated Electrons · Physics 2016-01-27 John R. Tolsma , Alessandro Principi , Reza Asgari , Marco Polini , Allan H. MacDonald

Direct electron spin resonance (ESR) on a high mobility two dimensional electron gas in a single AlAs quantum well reveals an electronic $g$-factor of 1.991 at 9.35 GHz and 1.989 at 34 GHz with a minimum linewidth of 7 Gauss. The ESR…

Mesoscale and Nanoscale Physics · Physics 2009-11-11 M. Schulte , J. G. S. Lok , G. Denninger , W. Dietsche

Electrons can form a two-dimensional electron gas at metal surfaces, where lateral confinement leads to quantum-well states. Such states have been observed for highly itinerant electrons, but it remains an open question whether quantum-well…

We report magneto-transport measurements in wide GaAs quantum wells with tunable density to probe the stability of the fractional quantum Hall effect at filling factor $\nu = $ 5/2 in the vicinity of the crossing between Landau levels (LLs)…

Mesoscale and Nanoscale Physics · Physics 2012-03-06 Yang Liu , D. Kamburov , M. Shayegan , L. N. Pfeiffer , K. W. West , K. W. Baldwin

The two-dimensional electron system (2DES) is a unique laboratory for the physics of interacting particles. Application of a large magnetic field produces massively degenerate quantum levels known as Landau levels. Within a Landau level the…

Mesoscale and Nanoscale Physics · Physics 2010-05-24 O. E. Dial , R. C. Ashoori , L. N. Pfeiffer , K. W. West
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