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J K Jain - One of the best experts on this subject based on the ideXlab platform.
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Non-Abelian fractional quantum Hall state at 3/7 -filled Landau Level
Phys.Rev.Res., 2020Co-Authors: W.n. Faugno, J K Jain, Ajit C BalramAbstract:We consider a non-Abelian candidate state at filling factor ν=3/7 state belonging to the parton family. We find that, in the second Landau Level of GaAs (i.e., at filling factor ν=2+3/7), this state is energetically superior to the standard Jain composite-fermion state and also provides a very good representation of the ground state found in exact diagonalization studies of finite systems. This leads us to predict that if a fractional quantum Hall effect is observed at ν=3/7 in the second Landau Level, it is likely to be described by this new non-Abelian state. We enumerate experimentally measurable properties that can verify the topological structure of this state.
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crystallization in the fractional quantum hall regime induced by Landau Level mixing
Physical Review Letters, 2018Co-Authors: Jianyun Zhao, Yuhe Zhang, J K JainAbstract:The interplay between strongly correlated liquid and crystal phases for two-dimensional electrons exposed to a high transverse magnetic field is of fundamental interest. Through the nonperturbative fixed-phase diffusion Monte Carlo method, we determine the phase diagram of the Wigner crystal in the $\ensuremath{\nu}\ensuremath{-}\ensuremath{\kappa}$ plane, where $\ensuremath{\nu}$ is the filling factor and $\ensuremath{\kappa}$ is the strength of Landau-Level (LL) mixing. The phase boundary is seen to exhibit a striking $\ensuremath{\nu}$ dependence, with the states away from the magic filling factors $\ensuremath{\nu}=n/(2pn+1)$ being much more susceptible to crystallization due to Landau-Level mixing than those at $\ensuremath{\nu}=n/(2pn+1)$. Our results explain the qualitative difference between the experimental behaviors observed in $n$- and $p$-doped gallium arsenide quantum wells and, in particular, the existence of an insulating state for $\ensuremath{\nu}l1/3$ and also for $1/3l\ensuremath{\nu}l2/5$ in low-density $p$-doped systems. We predict that, in the vicinity of $\ensuremath{\nu}=1/5$ and $\ensuremath{\nu}=2/9$, increasing LL mixing causes a transition not into an ordinary electron Wigner crystal, but rather into a strongly correlated crystal of composite fermions carrying two vortices.
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berry phase of the composite fermion fermi sea effect of Landau Level mixing
Physical Review B, 2018Co-Authors: Mikael Fremling, J K JainAbstract:We construct explicit lowest-Landau-Level wave functions for the composite-fermion Fermi sea and its low-energy excitations following a recently developed approach [Pu, Wu, and Jain, Phys. Rev. B 96, 195302 (2017)2469-995010.1103/PhysRevB.96.195302] and demonstrate them to be very accurate representations of the Coulomb eigenstates. We further ask how the Berry phase associated with a closed loop around the Fermi circle, predicted to be π in a Dirac composite fermion theory satisfying particle-hole symmetry [D. T. Son, Phys. Rev. X 5, 031027 (2015)2160-330810.1103/PhysRevX.5.031027], is affected by Landau-Level mixing. For this purpose, we consider a simple model wherein we determine the variational ground state as a function of Landau-Level mixing within the space spanned by two basis functions: the lowest-Landau-Level projected and the unprojected composite-fermion Fermi sea wave functions. We evaluate Berry phase for a path around the Fermi circle within this model following a recent prescription, and find that it rotates rapidly as a function of Landau-Level mixing. We also consider the effect of a particle-hole symmetry-breaking three-body interaction on the Berry phase while confining the Hilbert space to the lowest Landau Level. Our study deepens the connection between the π Berry phase and the exact particle-hole symmetry in the lowest Landau Level.
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Landau Level mixing and particle hole symmetry breaking for spin transitions in the fractional quantum hall effect
Physical Review Letters, 2016Co-Authors: Yuhe Zhang, J K Jain, Arkadiusz WojsAbstract:The spin transitions in the fractional quantum Hall effect provide a direct measure of the tiny energy differences between differently spin-polarized states and thereby serve as an extremely sensitive test of the quantitative accuracy of the theory of the fractional quantum Hall effect, and, in particular, of the role of Landau-Level mixing in lifting the particle-hole symmetry. We report on an accurate quantitative study of this physics, evaluating the effect of Landau-Level mixing in a nonperturbative manner using a fixed-phase diffusion Monte Carlo method. We find excellent agreement between our calculated critical Zeeman energies and the experimentally measured values. In particular, we find, as also do experiments, that the critical Zeeman energies for fractional quantum Hall states at filling factors ν=2-n/(2n±1) are significantly higher than those for ν=n/(2n±1), a quantitative signature of the lifting of particle-hole symmetry due to Landau-Level mixing.
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spontaneous polarization of composite fermions in the n 1 Landau Level of graphene
Physical Review B, 2015Co-Authors: Ajit C Balram, Csaba Tőke, Arkadiusz Wojs, J K JainAbstract:Motivated by recent experiments that reveal expansive fractional quantum Hall states in the $n=1$ graphene Landau Level and suggest a nontrivial role of the spin degree of freedom [Amet {\em et al.}, Nat. Commun. {\bf 6}, 5838 (2014)], we perform accurate quantitative study of the the competition between fractional quantum Hall states with different spin polarizations. We find that the fractional quantum Hall effect is well described in terms of composite fermions, but the spin physics is qualitatively different from that in the $n=0$ Landau Level. In particular, for the states at filling factors $n/(2n\pm 1)$, both exact diagonalization and the composite fermion theory show that the ground state is fully spin polarized and supports a robust spin wave mode even in the limit of vanishing Zeeman coupling. Thus, even though composite fermions are formed, a mean field description that treats them as weakly interacting particles breaks down, and the exchange interaction between them is strong enough to cause a qualitative change in the behavior by inducing full spin polarization. We also verify that the fully spin polarized composite fermion Fermi sea has lower energy than the paired Pfaffian state at the relevant half fillings in the $n=1$ graphene Landau Level, indicating a lack of fractional quantum Hall effect at half filling in the $n=1$ graphene Landau Level.
Joost Slingerland - One of the best experts on this subject based on the ideXlab platform.
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Fractional quantum Hall hierarchy and the second Landau Level
Physical Review B, 2008Co-Authors: Parsa Bonderson, Joost SlingerlandAbstract:We generalize the fractional quantum Hall hierarchy picture to apply to arbitrary, possibly non-Abelian, fractional quantum Hall states. Applying this to the nu = 5/2 Moore-Read state, we construct new explicit trial wavefunctions to describe the fractional quantum Hall effect in the second Landau Level. The resulting hierarchy of states, which reproduces the filling fractions of all observed Hall conductance plateaus in the second Landau Level, is characterized by electron pairing in the ground state and an excitation spectrum that includes non-Abelian anyons of the Ising type. We propose this as a unifying picture in which p-wave pairing characterizes the fractional quantum Hall effect in the second Landau Level.
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Fractional Quantum Hall Hierarchy and the Second Landau Level
Bulletin of the American Physical Society, 2008Co-Authors: Parsa Bonderson, Joost SlingerlandAbstract:We generalize the fractional quantum Hall hierarchy picture to apply to arbitrary, possibly non-Abelian, fractional quantum Hall states. Applying this to the nu=5/2 Moore-Read state, we construct explicit trial wave functions to describe the fractional quantum Hall effect in the second Landau Level. The resulting hierarchy of states, which reproduces the filling fractions of all observed Hall conductance plateaus in the second Landau Level, is characterized by electron pairing in the ground state and an excitation spectrum that includes non-Abelian anyons of the Ising type. We propose this as a unifying picture in which p-wave pairing characterizes the fractional quantum Hall effect in the second Landau Level.
K W West - One of the best experts on this subject based on the ideXlab platform.
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particle hole symmetry and the fractional quantum hall effect in the lowest Landau Level
Physical Review Letters, 2020Co-Authors: W Pan, K W West, Loren Pfeiffer, W Kang, M P Lilly, John L Reno, K W Baldwin, D C TsuiAbstract:We report on detailed experimental studies of a high-quality heterojunction insulated-gate field-effect transistor (HIGFET) to probe the particle-hole symmetry of the fractional quantum Hall effect (FQHE) states about half-filling in the lowest Landau Level. The HIGFET is specially designed to vary the density of a two-dimensional electronic system under constant magnetic fields. We find in our constant magnetic field, variable density measurements that the sequence of FQHE states at filling factors ν=1/3,2/5,3/7… and its particle-hole conjugate states at filling factors 1-ν=2/3,3/5,4/7… have a very similar energy gap. Moreover, a reflection symmetry can be established in the magnetoconductivities between the ν and 1-ν states about half-filling. Our results demonstrate that the FQHE states in the lowest Landau Level are manifestly particle-hole symmetric.
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optical emission spectroscopy study of competing phases of electrons in the second Landau Level
Physical Review Letters, 2016Co-Authors: Antonio Levy, K W West, M J Manfra, Loren Pfeiffer, Ursula Wurstbauer, Yuliya Y Kuznetsova, Aron Pinczuk, G C Gardner, J D WatsonAbstract:Quantum phases of electrons in the filling factor range 2≤ν≤3 are probed by the weak optical emission from the partially populated second Landau Level and spin wave measurements. Observations of optical emission include a multiplet of sharp peaks that exhibit a strong filling factor dependence. Spin wave measurements by resonant inelastic light scattering probe breaking of spin rotational invariance and are used to link this optical emission with collective phases of electrons. A remarkably rapid interplay between emission peak intensities manifests phase competition in the second Landau Level.
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nonconventional odd denominator fractional quantum hall states in the second Landau Level
Physical Review Letters, 2010Co-Authors: Ashwani Kumar, G A Csathy, M J Manfra, Loren Pfeiffer, K W WestAbstract:We report the observation of a new fractional quantum Hall state in the second Landau Level of a two-dimensional electron gas at the Landau Level filling factor ν=2+6/13. We find that the model of noninteracting composite fermions can explain the magnitude of gaps of the prominent 2+1/3 and 2+2/3 states. The same model fails, however, to account for the gaps of the 2+2/5 and the newly observed 2+6/13 states suggesting that these two states are of exotic origin.
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tilt induced localization and delocalization in the second Landau Level
Physical Review Letters, 2005Co-Authors: Gabor Csathy, C L Vicente, E D Adams, N S Sullivan, H L Stormer, D C Tsui, L N Pfeiffer, K W WestAbstract:We have investigated the behavior of electronic phases of the second Landau Level under tilted magnetic fields. The fractional quantum Hall liquids at $\nu=$2+1/5 and 2+4/5 and the solid phases at $\nu=$2.30, 2.44, 2.57, and 2.70 are quickly destroyed with tilt. This behavior can be interpreted as a tilt driven localization of the 2+1/5 and 2+4/5 fractional quantum Hall liquids and a delocalization through melting of solid phases in the top Landau Level, respectively. The evolution towards the classical Hall gas of the solid phases is suggestive of antiferromagnetic ordering.
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insulating and fractional quantum hall states in the first excited Landau Level
Physical Review Letters, 2002Co-Authors: J P Eisenstein, Loren Pfeiffer, K B Cooper, K W WestAbstract:The observation of new insulating phases of two-dimensional electrons in the first excited Landau Level is reported. These states, which are manifested as reentrant integer quantized Hall effects, exist alongside well-developed even-denominator fractional quantized Hall states at ν = 7/2 and 5/2 and new odd-denominator states at ν = 3+1/5 and 3+4/5.
Parsa Bonderson - One of the best experts on this subject based on the ideXlab platform.
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Fractional quantum Hall hierarchy and the second Landau Level
Physical Review B, 2008Co-Authors: Parsa Bonderson, Joost SlingerlandAbstract:We generalize the fractional quantum Hall hierarchy picture to apply to arbitrary, possibly non-Abelian, fractional quantum Hall states. Applying this to the nu = 5/2 Moore-Read state, we construct new explicit trial wavefunctions to describe the fractional quantum Hall effect in the second Landau Level. The resulting hierarchy of states, which reproduces the filling fractions of all observed Hall conductance plateaus in the second Landau Level, is characterized by electron pairing in the ground state and an excitation spectrum that includes non-Abelian anyons of the Ising type. We propose this as a unifying picture in which p-wave pairing characterizes the fractional quantum Hall effect in the second Landau Level.
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Fractional Quantum Hall Hierarchy and the Second Landau Level
Bulletin of the American Physical Society, 2008Co-Authors: Parsa Bonderson, Joost SlingerlandAbstract:We generalize the fractional quantum Hall hierarchy picture to apply to arbitrary, possibly non-Abelian, fractional quantum Hall states. Applying this to the nu=5/2 Moore-Read state, we construct explicit trial wave functions to describe the fractional quantum Hall effect in the second Landau Level. The resulting hierarchy of states, which reproduces the filling fractions of all observed Hall conductance plateaus in the second Landau Level, is characterized by electron pairing in the ground state and an excitation spectrum that includes non-Abelian anyons of the Ising type. We propose this as a unifying picture in which p-wave pairing characterizes the fractional quantum Hall effect in the second Landau Level.
G. Bauer - One of the best experts on this subject based on the ideXlab platform.
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Landau Level spectroscopy of Bi 2 Te 3
Physical Review B, 2020Co-Authors: I. Mohelský, Adam Dubroka, J. Wyzula, A. Slobodeniuk, Gerard Martinez, Y. Krupko, Benjamin A. Piot, Ondřej Caha, Josef Humlíček, G. BauerAbstract:Here we report on Landau Level spectroscopy in magnetic fields up to 34 T performed on a thin film of topological insulator Bi$_2$Te$_3$ epitaxially grown on a BaF$_2$ substrate. The observed response is consistent with the picture of a direct-gap semiconductor in which charge carriers closely resemble massive Dirac particles. The fundamental band gap reaches $E_g=(175\pm 5)$~meV at low temperatures and it is not located on the trigonal axis, thus displaying either six or twelvefold valley degeneracy. Notably, our magneto-optical data do not indicate any band inversion. This suggests that the fundamental band gap is relatively distant from the $\Gamma$ point where profound inversion exists andgives rise to relativistic-like surface states of Bi$_2$Te$_3$.
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Landau Level spectroscopy of Bi 2 Te 3
Physical Review B, 2020Co-Authors: I. Mohelský, Adam Dubroka, J. Wyzula, A. Slobodeniuk, Gerard Martinez, Y. Krupko, Ondřej Caha, Josef Humlíček, B Piot, G. BauerAbstract:Here we report on Landau Level spectroscopy in magnetic fields up to 34 T performed on a thin film of the topological insulator Bi 2 Te 3 epitaxially grown on a BaF 2 substrate. The observed response is consistent with the picture of a direct-gap semiconductor in which charge carriers closely resemble massive Dirac particles. The fundamental band gap reaches E g = (175 ± 5) meV at low temperatures and it is not located on the trigonal axis, thus displaying either sixfold or twelvefold valley degeneracy. Interestingly, our magneto-optical data do not indicate any band inversion at the direct gap. This suggests that the fundamental band gap is relatively distant from the point where profound inversion exists and gives rise to the relativisticlike surface states of Bi 2 Te 3 .
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negative longitudinal magnetoresistance from the anomalous n 0 Landau Level in topological materials
Physical Review Letters, 2017Co-Authors: Badih A Assaf, G. Bauer, T Phuphachong, Erik Kampert, V V Volobuev, Parthasarathi Mandal, J Sanchezbarriga, O Rader, G SpringholzAbstract:Negative longitudinal magnetoresistance (NLMR) is shown to occur in topological materials in the extreme quantum limit, when a magnetic field is applied parallel to the excitation current. We perform pulsed and DC field measurements on Pb1-xSnxSe epilayers where the topological state can be chemically tuned. The NLMR is observed in the topological state, but is suppressed and becomes positive when the system becomes trivial. In a topological material, the lowest N=0 conduction Landau Level disperses down in energy as a function of increasing magnetic field, while the N=0 valence Landau Level disperses upwards. This anomalous behavior is shown to be responsible for the observed NLMR. Our work provides an explanation of the outstanding question of NLMR in topological insulators and establishes this effect as a possible hallmark of bulk conduction in topological matter.
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Negative Longitudinal Magnetoresistance from the Anomalous N = 0 Landau Level in Topological Materials
Physical Review Letters, 2017Co-Authors: B. a. Assaf, G. Bauer, T Phuphachong, Erik Kampert, V V Volobuev, O Rader, G Springholz, P. s. Mandal, J. Sánchez-barriga, L. a. De VaulchierAbstract:Negative longitudinal magnetoresistance (NLMR) is shown to occur in topological materials in the extreme quantum limit, when a magnetic field is applied parallel to the excitation current. We perform pulsed and DC field measurements on Pb1-xSnxSe epilayers where the topological state can be chemically tuned. The NLMR is observed in the topological state, but is suppressed and becomes positive when the system becomes trivial. In a topological material, the lowest N=0 conduction Landau Level disperses down in energy as a function of increasing magnetic field, while the N=0 valence Landau Level disperses upwards. This anomalous behavior is shown to be responsible for the observed NLMR. Our work provides an explanation of the outstanding question of NLMR in topological insulators and establishes this effect as a possible hallmark of bulk conduction in topological matter.
