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David Neilson - One of the best experts on this subject based on the ideXlab platform.
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three dimensional electron hole Superfluidity in a superlattice close to room temperature
Physical Review B, 2020Co-Authors: M Van Der Donck, Sara Conti, Andrea Perali, A Hamilton, F M Peeters, David Neilson, B PartoensAbstract:Although there is strong theoretical and experimental evidence for electron-hole Superfluidity in separated sheets of electrons and holes at low $T$, extending Superfluidity to high $T$ is limited by strong two-dimensional fluctuations and Kosterlitz-Thouless effects. We show this limitation can be overcome using a superlattice of alternating electron- and hole-doped semiconductor monolayers. The superfluid transition in a three-dimensional superlattice is not topological, and for strong electron-hole pair coupling, the transition temperature ${T}_{c}$ can be at room temperature. As a quantitative illustration, we show ${T}_{c}$ can reach $270\phantom{\rule{4pt}{0ex}}\mathrm{K}$ for a superfluid in a realistic superlattice of transition metal dichalcogenide monolayers.
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experimental conditions for the observation of electron hole Superfluidity in gaas heterostructures
Physical Review B, 2020Co-Authors: S Saberipouya, Sara Conti, Andrea Perali, A F Croxall, A Hamilton, F M Peeters, David NeilsonAbstract:The experimental parameter ranges needed to generate Superfluidity in optical and drag experiments in GaAs double quantum wells are determined using a formalism that includes self-consistent screening of the Coulomb pairing interaction in the presence of the superfluid. The very different electron and hole masses in GaAs make this a particularly interesting system for Superfluidity with exotic superfluid phases predicted in the BCS-Bose-Einstein condensation crossover regime. We find that the density and temperature ranges for Superfluidity cover the range for which optical experiments have observed indications of Superfluidity but that existing drag experiments lie outside the superfluid range. We also show that, for samples with low mobility with no macroscopically connected Superfluidity, if the Superfluidity survives in randomly distributed localized pockets, standard quantum capacitance measurements could detect these pockets.
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three dimensional electron hole Superfluidity in a superlattice close to room temperature
arXiv: Superconductivity, 2019Co-Authors: M Van Der Donck, Sara Conti, Andrea Perali, A Hamilton, F M Peeters, David Neilson, B PartoensAbstract:Although there is strong theoretical and experimental evidence for electron-hole Superfluidity in separated sheets of electrons and holes at low $T$, extending Superfluidity to high $T$ is limited by strong 2D fluctuations and Kosterlitz-Thouless effects. We show this limitation can be overcome using a superlattice of alternating electron- and hole-doped semiconductor monolayers. The superfluid transition in a 3D superlattice is not topological, and for strong electron-hole pair coupling, the transition temperature $T_c$ can be at room temperature. As a quantitative illustration, we show $T_c$ can reach $270$ K for a superfluid in a realistic superlattice of transition metal dichalcogenide monolayers.
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evidence from quantum monte carlo simulations of large gap Superfluidity and bcs bec crossover in double electron hole layers
Physical Review Letters, 2018Co-Authors: Pablo Lopez Rios, Andrea Perali, David Neilson, R J NeedsAbstract:We report quantum Monte Carlo evidence of the existence of large gap Superfluidity in electron-hole double layers over wide density ranges. The superfluid parameters evolve from normal state to BEC with decreasing density, with the BCS state restricted to a tiny range of densities due to the strong screening of Coulomb interactions, which causes the gap to rapidly become large near the onset of Superfluidity. The superfluid properties exhibit similarities to ultracold fermions and iron-based superconductors, suggesting an underlying universal behavior of BCS-BEC crossovers in pairing systems.
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multicomponent electron hole Superfluidity and the bcs bec crossover in double bilayer graphene
Physical Review Letters, 2017Co-Authors: Sara Conti, Andrea Perali, F M Peeters, David NeilsonAbstract:Superfluidity in coupled electron-hole sheets of bilayer graphene is predicted here to be multicomponent because of the conduction and valence bands. We investigate the superfluid crossover properties as functions of the tunable carrier densities and the tunable energy band gap E_{g}. For small band gaps there is a significant boost in the two superfluid gaps, but the interaction-driven excitations from the valence to the conduction band can weaken the Superfluidity, even blocking the system from entering the Bose-Einstein condensate (BEC) regime at low densities. At a given larger density, a band gap E_{g}∼80-120 meV can carry the system into the strong-pairing multiband BCS-BEC crossover regime, the optimal range for realization of high-T_{c} Superfluidity.
Andrea Perali - One of the best experts on this subject based on the ideXlab platform.
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three dimensional electron hole Superfluidity in a superlattice close to room temperature
Physical Review B, 2020Co-Authors: M Van Der Donck, Sara Conti, Andrea Perali, A Hamilton, F M Peeters, David Neilson, B PartoensAbstract:Although there is strong theoretical and experimental evidence for electron-hole Superfluidity in separated sheets of electrons and holes at low $T$, extending Superfluidity to high $T$ is limited by strong two-dimensional fluctuations and Kosterlitz-Thouless effects. We show this limitation can be overcome using a superlattice of alternating electron- and hole-doped semiconductor monolayers. The superfluid transition in a three-dimensional superlattice is not topological, and for strong electron-hole pair coupling, the transition temperature ${T}_{c}$ can be at room temperature. As a quantitative illustration, we show ${T}_{c}$ can reach $270\phantom{\rule{4pt}{0ex}}\mathrm{K}$ for a superfluid in a realistic superlattice of transition metal dichalcogenide monolayers.
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experimental conditions for the observation of electron hole Superfluidity in gaas heterostructures
Physical Review B, 2020Co-Authors: S Saberipouya, Sara Conti, Andrea Perali, A F Croxall, A Hamilton, F M Peeters, David NeilsonAbstract:The experimental parameter ranges needed to generate Superfluidity in optical and drag experiments in GaAs double quantum wells are determined using a formalism that includes self-consistent screening of the Coulomb pairing interaction in the presence of the superfluid. The very different electron and hole masses in GaAs make this a particularly interesting system for Superfluidity with exotic superfluid phases predicted in the BCS-Bose-Einstein condensation crossover regime. We find that the density and temperature ranges for Superfluidity cover the range for which optical experiments have observed indications of Superfluidity but that existing drag experiments lie outside the superfluid range. We also show that, for samples with low mobility with no macroscopically connected Superfluidity, if the Superfluidity survives in randomly distributed localized pockets, standard quantum capacitance measurements could detect these pockets.
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three dimensional electron hole Superfluidity in a superlattice close to room temperature
arXiv: Superconductivity, 2019Co-Authors: M Van Der Donck, Sara Conti, Andrea Perali, A Hamilton, F M Peeters, David Neilson, B PartoensAbstract:Although there is strong theoretical and experimental evidence for electron-hole Superfluidity in separated sheets of electrons and holes at low $T$, extending Superfluidity to high $T$ is limited by strong 2D fluctuations and Kosterlitz-Thouless effects. We show this limitation can be overcome using a superlattice of alternating electron- and hole-doped semiconductor monolayers. The superfluid transition in a 3D superlattice is not topological, and for strong electron-hole pair coupling, the transition temperature $T_c$ can be at room temperature. As a quantitative illustration, we show $T_c$ can reach $270$ K for a superfluid in a realistic superlattice of transition metal dichalcogenide monolayers.
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high temperature electron hole Superfluidity with strong anisotropic gaps in double phosphorene monolayers
Physical Review B, 2018Co-Authors: S Saberipouya, Andrea Perali, M Zarenia, T Vazifehshenas, F M PeetersAbstract:Excitonic Superfluidity in double phosphorene monolayers is investigated using the BCS mean-field equations. Highly anisotropic Superfluidity is predicted where we found that the maximum superfluid gap is in the BEC regime along the armchair direction and in the BCS-BEC crossover regime along the zigzag direction. We estimate the highest Kosterlitz-Thouless transition temperature with maximum value up to $\sim 90$ K with onset carrier densities as high as $4 \times 10^{12}$ cm$^{-2}$. This transition temperature is significantly larger than what is found in double electron-hole few-layers of graphene. Our results can guide experimental research towards the realization of anisotropic condensate states in electron-hole phosphorene monolayers.
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evidence from quantum monte carlo simulations of large gap Superfluidity and bcs bec crossover in double electron hole layers
Physical Review Letters, 2018Co-Authors: Pablo Lopez Rios, Andrea Perali, David Neilson, R J NeedsAbstract:We report quantum Monte Carlo evidence of the existence of large gap Superfluidity in electron-hole double layers over wide density ranges. The superfluid parameters evolve from normal state to BEC with decreasing density, with the BCS state restricted to a tiny range of densities due to the strong screening of Coulomb interactions, which causes the gap to rapidly become large near the onset of Superfluidity. The superfluid properties exhibit similarities to ultracold fermions and iron-based superconductors, suggesting an underlying universal behavior of BCS-BEC crossovers in pairing systems.
Sara Conti - One of the best experts on this subject based on the ideXlab platform.
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three dimensional electron hole Superfluidity in a superlattice close to room temperature
Physical Review B, 2020Co-Authors: M Van Der Donck, Sara Conti, Andrea Perali, A Hamilton, F M Peeters, David Neilson, B PartoensAbstract:Although there is strong theoretical and experimental evidence for electron-hole Superfluidity in separated sheets of electrons and holes at low $T$, extending Superfluidity to high $T$ is limited by strong two-dimensional fluctuations and Kosterlitz-Thouless effects. We show this limitation can be overcome using a superlattice of alternating electron- and hole-doped semiconductor monolayers. The superfluid transition in a three-dimensional superlattice is not topological, and for strong electron-hole pair coupling, the transition temperature ${T}_{c}$ can be at room temperature. As a quantitative illustration, we show ${T}_{c}$ can reach $270\phantom{\rule{4pt}{0ex}}\mathrm{K}$ for a superfluid in a realistic superlattice of transition metal dichalcogenide monolayers.
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experimental conditions for the observation of electron hole Superfluidity in gaas heterostructures
Physical Review B, 2020Co-Authors: S Saberipouya, Sara Conti, Andrea Perali, A F Croxall, A Hamilton, F M Peeters, David NeilsonAbstract:The experimental parameter ranges needed to generate Superfluidity in optical and drag experiments in GaAs double quantum wells are determined using a formalism that includes self-consistent screening of the Coulomb pairing interaction in the presence of the superfluid. The very different electron and hole masses in GaAs make this a particularly interesting system for Superfluidity with exotic superfluid phases predicted in the BCS-Bose-Einstein condensation crossover regime. We find that the density and temperature ranges for Superfluidity cover the range for which optical experiments have observed indications of Superfluidity but that existing drag experiments lie outside the superfluid range. We also show that, for samples with low mobility with no macroscopically connected Superfluidity, if the Superfluidity survives in randomly distributed localized pockets, standard quantum capacitance measurements could detect these pockets.
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three dimensional electron hole Superfluidity in a superlattice close to room temperature
arXiv: Superconductivity, 2019Co-Authors: M Van Der Donck, Sara Conti, Andrea Perali, A Hamilton, F M Peeters, David Neilson, B PartoensAbstract:Although there is strong theoretical and experimental evidence for electron-hole Superfluidity in separated sheets of electrons and holes at low $T$, extending Superfluidity to high $T$ is limited by strong 2D fluctuations and Kosterlitz-Thouless effects. We show this limitation can be overcome using a superlattice of alternating electron- and hole-doped semiconductor monolayers. The superfluid transition in a 3D superlattice is not topological, and for strong electron-hole pair coupling, the transition temperature $T_c$ can be at room temperature. As a quantitative illustration, we show $T_c$ can reach $270$ K for a superfluid in a realistic superlattice of transition metal dichalcogenide monolayers.
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multicomponent electron hole Superfluidity and the bcs bec crossover in double bilayer graphene
Physical Review Letters, 2017Co-Authors: Sara Conti, Andrea Perali, F M Peeters, David NeilsonAbstract:Superfluidity in coupled electron-hole sheets of bilayer graphene is predicted here to be multicomponent because of the conduction and valence bands. We investigate the superfluid crossover properties as functions of the tunable carrier densities and the tunable energy band gap E_{g}. For small band gaps there is a significant boost in the two superfluid gaps, but the interaction-driven excitations from the valence to the conduction band can weaken the Superfluidity, even blocking the system from entering the Bose-Einstein condensate (BEC) regime at low densities. At a given larger density, a band gap E_{g}∼80-120 meV can carry the system into the strong-pairing multiband BCS-BEC crossover regime, the optimal range for realization of high-T_{c} Superfluidity.
Stephane Kenacohen - One of the best experts on this subject based on the ideXlab platform.
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room temperature Superfluidity in a polariton condensate
Nature Physics, 2017Co-Authors: Giovanni Lerario, Antonio Fieramosca, Fabio Barachati, D Ballarini, Konstantinos S Daskalakis, Lorenzo Dominici, Milena De Giorgi, Stefan A Maier, Giuseppe Gigli, Stephane KenacohenAbstract:Superfluidity is a phenomenon usually restricted to cryogenic temperatures, but organic microcavities provide the conditions for a superfluid flow of polaritons at room temperature. Superfluidity—the suppression of scattering in a quantum fluid at velocities below a critical value—is one of the most striking manifestations of the collective behaviour typical of Bose–Einstein condensates1. This phenomenon, akin to superconductivity in metals, has until now been observed only at prohibitively low cryogenic temperatures. For atoms, this limit is imposed by the small thermal de Broglie wavelength, which is inversely related to the particle mass. Even in the case of ultralight quasiparticles such as exciton-polaritons, Superfluidity has been demonstrated only at liquid helium temperatures2. In this case, the limit is not imposed by the mass, but instead by the small binding energy of Wannier–Mott excitons, which sets the upper temperature limit. Here we demonstrate a transition from supersonic to superfluid flow in a polariton condensate under ambient conditions. This is achieved by using an organic microcavity supporting stable Frenkel exciton-polaritons at room temperature. This result paves the way not only for tabletop studies of quantum hydrodynamics, but also for room-temperature polariton devices that can be robustly protected from scattering.
Wolfgang Ketterle - One of the best experts on this subject based on the ideXlab platform.
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phase diagram of a two component fermi gas with resonant interactions
Nature, 2008Co-Authors: Yongil Shin, Andre Schirotzek, Christian H. Schunck, Wolfgang KetterleAbstract:A major controversy has surrounded the stability of Superfluidity in spin-polarized Fermi gas systems with resonant interactions when the 'up' and 'down' spin components are imbalanced. This problem is explored for a Fermi gas of 6Li atoms, using tomographic techniques to map out the superfluid phases as the temperature and density imbalance are varied. Evidence is found for various types of phase transitions, enabling quantitative tests of theoretical calculations on the stability of resonant Superfluidity. The pairing of fermions lies at the heart of superconductivity and Superfluidity. The stability of these pairs determines the robustness of the superfluid state, and the quest for superconductors with high critical temperature equates to a search for systems with strong pairing mechanisms. Ultracold atomic Fermi gases present a highly controllable model system for studying strongly interacting fermions1. Tunable interactions (through Feshbach collisional resonances) and the control of population or mass imbalance among the spin components provide unique opportunities to investigate the stability of pairing2,3,4—and possibly to search for exotic forms of Superfluidity5,6. A major controversy has surrounded the stability of Superfluidity against an imbalance between the two spin components when the fermions interact resonantly (that is, at unitarity). Here we present the phase diagram of a spin-polarized Fermi gas of 6Li atoms at unitarity, experimentally mapping out the superfluid phases versus temperature and density imbalance. Using tomographic techniques, we reveal spatial discontinuities in the spin polarization; this is the signature of a first-order superfluid-to-normal phase transition, and disappears at a tricritical point where the nature of the phase transition changes from first-order to second-order. At zero temperature, there is a quantum phase transition from a fully paired superfluid to a partially polarized normal gas. These observations and the implementation of an in situ ideal gas thermometer provide quantitative tests of theoretical calculations on the stability of resonant Superfluidity.
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Fermionic Superfluidity with Imbalanced Spin Populations
Science (New York N.Y.), 2005Co-Authors: Martin Zwierlein, Andre Schirotzek, Christian H. Schunck, Wolfgang KetterleAbstract:We established Superfluidity in a two-state mixture of ultracold fermionic atoms with imbalanced state populations. This study relates to the long-standing debate about the nature of the superfluid state in Fermi systems. Indicators for Superfluidity were condensates of fermion pairs and vortices in rotating clouds. For strong interactions, near a Feshbach resonance, Superfluidity was observed for a broad range of population imbalances. We mapped out the superfluid regime as a function of interaction strength and population imbalance and characterized the quantum phase transition to the normal state, known as the Pauli limit of Superfluidity.
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vortices and Superfluidity in a strongly interacting fermi gas
Nature, 2005Co-Authors: Martin Zwierlein, Christian H. Schunck, J R Aboshaeer, A Schirotzek, Wolfgang KetterleAbstract:Quantum degenerate Fermi gases provide a remarkable opportunity to study strongly interacting fermions. In contrast to other Fermi systems, such as superconductors, neutron stars or the quark-gluon plasma of the early Universe, these gases have low densities and their interactions can be precisely controlled over an enormous range. Previous experiments with Fermi gases have revealed condensation of fermion pairs. Although these and other studies were consistent with predictions assuming Superfluidity, proof of superfluid behaviour has been elusive. Here we report observations of vortex lattices in a strongly interacting, rotating Fermi gas that provide definitive evidence for Superfluidity. The interaction and therefore the pairing strength between two 6Li fermions near a Feshbach resonance can be controlled by an external magnetic field. This allows us to explore the crossover from a Bose–Einstein condensate of molecules to a Bardeen–Cooper–Schrieffer superfluid of loosely bound pairs. The crossover is associated with a new form of Superfluidity that may provide insights into high-transition-temperature superconductors. A clear signature for Superfluidity — the frictionless flow seen in some liquids at temperatures close to absolute zero — is the formation of a lattice of quantum vortices in a rotating system. This ‘smoking gun’ has been observed for the first time in an ultracold gas of lithium-6 atoms, confirming the prediction that these quantum gases are superfluids. This system could be a useful model for studies on high-temperature superconductivity and exotic matter such as quark–gluon plasma or neutron stars.
