Commensurability Oscillations of Composite Fermions Induced by the Periodic Potential of a Wigner Crystal

Deng, Hao; Liu, Y.; Jo, Insun; Pfeiffer, L. N.; West, K. W.; Baldwin, K. W.; Shayegan, M.

doi:10.1103/physrevlett.117.096601

Cited by 56 publications

(59 citation statements)

References 34 publications

(42 reference statements)

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“…Distinct features related with compressibility in surface-acoustic-wave propagation on high-quality AlGaAs/GaAs heterostructures were observed by Willett et al [10][11][12]. Furthermore, resonances at fields where the classical cyclotron orbit becomes commensurate with a superlattice have been found [13,14]. Strong enhancement of composite fermion mass near half filling ν = 1/2 has been observed in experiments on similar 2D electron gas heterostructures [15,16].…”

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confidence: 56%

Weak antilocalization of composite fermions in graphene

2018

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Composite fermions in fractional quantum Hall (FQH) systems are believed to form a Fermi sea of weakly interacting particles at half filling ν = 1/2. Recently, it was proposed (D. T. Son, Phys. Rev. X 5, 031027 (2015)) that these composite fermions are Dirac particles. In our work, we demonstrate experimentally that composite fermions found in monolayer graphene are Dirac particles at half filling. Our experiments have addressed FQH states in high-mobility, suspended graphene Corbino disks in the vicinity of ν = 1/2. We find strong temperature dependence of conductivity σ away from half filling, which is consistent with the expected electron-electron interaction induced gaps in the FQH state. At half filling, however, the temperature dependence of conductivity σ(T ) becomes quite weak as expected for a Fermi sea of composite fermions and we find only logarithmic dependence of σ on T . The sign of this quantum correction coincides with weak antilocalization of composite fermions, which reveals the relativistic Dirac nature of composite fermions in graphene.The fractional quantum Hall (FQH) state is a many body phenomenon where fractionally charged elementary excitations lead to quantization of the Hall conductance at fractional filling factor ν = hn/(eB) at carrier density n and magnetic field B [1]. The generation of these incompressible liquid states requires a large Coulomb interaction energy compared with the disorder potential, putting strict requirements on temperature, the quality of the two-dimensional electron gas (2-DEG) and the strength of the magnetic field. Owing to reduced screening in atomically thin graphene, the electrons in graphene interact with larger Coulomb interaction energy than electrons in semiconductor heterostructures, providing an extraordinary setting for studies of FQH states and their description in terms of composite fermions [2][3][4].The composite fermion theory [2] and Composite Fermion Chern-Simon (CFCS) theory have been very successful in outlining a unified picture of fractional quantum Hall effect. Lopez and Fradkin [5] showed that the problem of interacting electrons moving in 2D in the presence of an external magnetic field is equivalent to a fermion system, described by a Chern-Simon gauge field, where electrons are bound to even number of vortex lines. Fluctuations in the gauge field were soon realized to have strong influence on the quantum correction of the composite fermion conductivity [6]. Subsequently, a Fermi liquid type of theory was proposed for half-filled Landau level [7] where various observables in the low-temperature limit are described in terms of Fermi liquid parameters [8], involving most notably the effective mass m * for composite fermions, which is expected to have a strong enhancement near half filling.There is extensive experimental evidence in favor of weakly interacting Fermi sea of composite fermions effectively in a zero magnetic field at ν = 1/2. Transport anomalies in the lowest Landau level of two-dimensional electrons at half filling were ...

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confidence: 56%

Weak antilocalization of composite fermions in graphene

2018

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“…In a two-dimensional electron system (2DES), a quantum WC has long been expected to form at low temperature (T 1 K) and high magnetic field (B) when the electrons occupy the lowest Landau level and their kinetic energy is quenched [2][3][4]. There is also some experimental evidence, albeit often indirect, for the formation of such a magnetic-field-induced, quantum WC in very high-mobility (low-disorder) GaAs 2DESs near the Landau level filling factor ν = 1/5 [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. The main conclusion of these studies is that the WC, being pinned by the ubiquitous residual disorder, manifests in DC transport as an insulating phase with non-linear current-voltage (I-V) characteristics [7][8][9][10], and exhibits resonances in its high-frequency (microwave) AC transport which strongly suggest collective motions of the electrons [5, 9, 11-13, 15, 16].…”

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“…The main conclusion of these studies is that the WC, being pinned by the ubiquitous residual disorder, manifests in DC transport as an insulating phase with non-linear current-voltage (I-V) characteristics [7][8][9][10], and exhibits resonances in its high-frequency (microwave) AC transport which strongly suggest collective motions of the electrons [5, 9, 11-13, 15, 16]. In a recent bilayer experiment, a high-density layer hosting a composite fermion Fermi sea around ν = 1/2 was used to directly probe the microstructure of the WC forming in an adjacent, low-density layer [18].…”

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confidence: 99%

Probing the Melting of a Two-Dimensional Quantum Wigner Crystal via its Screening Efficiency

et al. 2019

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One of the most fundamental and yet elusive collective phases of an interacting electron system is the quantum Wigner crystal (WC), an ordered array of electrons expected to form when the electrons' Coulomb repulsion energy eclipses their kinetic (Fermi) energy. In low-disorder, twodimensional (2D) electron systems, the quantum WC is known to be favored at very low temperatures (T ) and small Landau level filling factors (ν), near the termination of the fractional quantum Hall states. This WC phase exhibits an insulating behavior, reflecting its pinning by the small but finite disorder potential. An experimental determination of a T vs ν phase diagram for the melting of the WC, however, has proved to be challenging. Here we use capacitance measurements to probe the 2D WC through its effective screening as a function of T and ν. We find that, as expected, the screening efficiency of the pinned WC is very poor at very low T and improves at higher T once the WC melts. Surprisingly, however, rather than monotonically changing with increasing T , the screening efficiency shows a well-defined maximum at a T which is close to the previously-reported melting temperature of the WC. Our experimental results suggest a new method to map out a T vs ν phase diagram of the magnetic-field-induced WC precisely.

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“…The ordered phase of electrons, where electrons localize themselves in a particular period or lattice, such as the skyrmion lattice or the Wigner lattice, has attracted considerable interest [1][2][3][4] . The existence of ordered phase in a two-dimensional (2D) system has been successfully probed by geometric resonance in magnetooscillations [1][2][3][4] . Despite observations of the incipient Wigner lattice in one-dimensional (1D) system by means of conductance measurements 5,6 , it is still challenging to monitor the ordered phase in a 1D system.…”

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confidence: 99%

Incipient singlet-triplet states in a hybrid mesoscopic system

et al. 2018

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In the present work we provide an easily accessible way to achieve the singlet-triplet Kondo effect in a hybrid system consisting of a quantum point contact (QPC) coupled to an electronic cavity. We show that by activating the coupling between the QPC and cavity, a zero-bias anomaly occurs in a low conductance regime, a coexistence of zero-bias and finite-bias anomaly (FBA) in a medium conductance regime, and a FBA-only anomaly in a high conductance regime. The latter two observations are due to the singlet-triplet Kondo effect. * uceeya3@ucl.ac.uk

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Commensurability Oscillations of Composite Fermions Induced by the Periodic Potential of a Wigner Crystal

Cited by 56 publications

References 34 publications

Weak antilocalization of composite fermions in graphene

Weak antilocalization of composite fermions in graphene

Probing the Melting of a Two-Dimensional Quantum Wigner Crystal via its Screening Efficiency

Incipient singlet-triplet states in a hybrid mesoscopic system

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