Pub Date : 2020-04-20DOI: 10.1103/physrevresearch.3.013007
L. Dominici, D. Colas, A. Gianfrate, A. Rahmani, V. Ardizzone, D. Ballarini, M. De Giorgi, G. Gigli, F. Laussy, D. Sanvitto, N. Voronova
Strongly-coupled quantum fluids, such as multi-component atomic condensates, optical fields and polaritons, are remarkable systems that allow to test the most fundamental symmetries and conservation laws of Physics. When the coupling between the components is coherent, not only the particles number, but also their phase texture that maps the linear and angular momentum, can be exchanged. Here, using optical pulses of different topologies and their coherent control, we excite the multi-component fluid of exciton-polaritons in such a way that all quantum states on the Bloch sphere are simultaneously present and undergo a structured Rabi-oscillatory dynamics. As a result, the complex light emitted from the cavity is characterized by inner phase singularity tubes spiraling around their axis of propagation, i.e., we observe a new kind of swirling vortices endowed with oscillating linear and orbital momentum, which exhibit ultrafast motion with striking accelerations beyond superluminal speed. This vortex motion is tracked by means of the stereographic projection, thanks to the created homeomorphism between the Bloch sphere and the real physical plane, and expressed in terms of the M"obius transformation.
{"title":"Full-Bloch beams and ultrafast Rabi-rotating vortices","authors":"L. Dominici, D. Colas, A. Gianfrate, A. Rahmani, V. Ardizzone, D. Ballarini, M. De Giorgi, G. Gigli, F. Laussy, D. Sanvitto, N. Voronova","doi":"10.1103/physrevresearch.3.013007","DOIUrl":"https://doi.org/10.1103/physrevresearch.3.013007","url":null,"abstract":"Strongly-coupled quantum fluids, such as multi-component atomic condensates, optical fields and polaritons, are remarkable systems that allow to test the most fundamental symmetries and conservation laws of Physics. When the coupling between the components is coherent, not only the particles number, but also their phase texture that maps the linear and angular momentum, can be exchanged. Here, using optical pulses of different topologies and their coherent control, we excite the multi-component fluid of exciton-polaritons in such a way that all quantum states on the Bloch sphere are simultaneously present and undergo a structured Rabi-oscillatory dynamics. As a result, the complex light emitted from the cavity is characterized by inner phase singularity tubes spiraling around their axis of propagation, i.e., we observe a new kind of swirling vortices endowed with oscillating linear and orbital momentum, which exhibit ultrafast motion with striking accelerations beyond superluminal speed. This vortex motion is tracked by means of the stereographic projection, thanks to the created homeomorphism between the Bloch sphere and the real physical plane, and expressed in terms of the M\"obius transformation.","PeriodicalId":8838,"journal":{"name":"arXiv: Quantum Gases","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87488162","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-04-17DOI: 10.21468/SCIPOSTPHYS.10.2.025
O. V. Marchukov, A. Volosniev
We employ the Gross-Pitaevskii equation to study acoustic emission generated in a uniform Bose gas by a static impurity. The impurity excites a sound-wave packet, which propagates through the gas. We calculate the shape of this wave packet in the limit of long wave lengths, and argue that it is possible to extract properties of the impurity by observing this shape. We illustrate here this possibility for a Bose gas with a trapped impurity atom -- an example of a relevant experimental setup. Presented results are general for all one-dimensional systems described by the nonlinear Schrodinger equation and can also be used in nonatomic systems, e.g., to analyze light propagation in nonlinear optical media. Finally, we calculate the shape of the sound-wave packet for a three-dimensional Bose gas assuming a spherically symmetric perturbation.
{"title":"Shape of a sound wave in a weakly-perturbed Bose gas","authors":"O. V. Marchukov, A. Volosniev","doi":"10.21468/SCIPOSTPHYS.10.2.025","DOIUrl":"https://doi.org/10.21468/SCIPOSTPHYS.10.2.025","url":null,"abstract":"We employ the Gross-Pitaevskii equation to study acoustic emission generated in a uniform Bose gas by a static impurity. The impurity excites a sound-wave packet, which propagates through the gas. We calculate the shape of this wave packet in the limit of long wave lengths, and argue that it is possible to extract properties of the impurity by observing this shape. We illustrate here this possibility for a Bose gas with a trapped impurity atom -- an example of a relevant experimental setup. Presented results are general for all one-dimensional systems described by the nonlinear Schrodinger equation and can also be used in nonatomic systems, e.g., to analyze light propagation in nonlinear optical media. Finally, we calculate the shape of the sound-wave packet for a three-dimensional Bose gas assuming a spherically symmetric perturbation.","PeriodicalId":8838,"journal":{"name":"arXiv: Quantum Gases","volume":"347 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76308855","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-04-15DOI: 10.1103/PHYSREVA.103.013317
N. Guenther, R. Schmidt, G. Bruun, V. Gurarie, P. Massignan
We analyze the properties of an impurity in a dilute Bose-Einstein condensate (BEC). First the quasiparticle residue of a static impurity in an ideal BEC is shown to vanish with increasing particle number as a stretched exponential, leading to a bosonic orthogonality catastrophe. Then we introduce a variational ansatz, which recovers this exact result and describes the macroscopic dressing of the impurity including its back-action onto the BEC as well as boson-boson repulsion beyond the Bogoliubov approximation. This ansatz predicts that the orthogonality catastrophe also occurs for mobile impurities, whenever the BEC becomes ideal. Finally, we show that our ansatz agrees well with experimental results.
{"title":"Mobile impurity in a Bose-Einstein condensate and the orthogonality catastrophe","authors":"N. Guenther, R. Schmidt, G. Bruun, V. Gurarie, P. Massignan","doi":"10.1103/PHYSREVA.103.013317","DOIUrl":"https://doi.org/10.1103/PHYSREVA.103.013317","url":null,"abstract":"We analyze the properties of an impurity in a dilute Bose-Einstein condensate (BEC). First the quasiparticle residue of a static impurity in an ideal BEC is shown to vanish with increasing particle number as a stretched exponential, leading to a bosonic orthogonality catastrophe. Then we introduce a variational ansatz, which recovers this exact result and describes the macroscopic dressing of the impurity including its back-action onto the BEC as well as boson-boson repulsion beyond the Bogoliubov approximation. This ansatz predicts that the orthogonality catastrophe also occurs for mobile impurities, whenever the BEC becomes ideal. Finally, we show that our ansatz agrees well with experimental results.","PeriodicalId":8838,"journal":{"name":"arXiv: Quantum Gases","volume":"28 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87682231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We develop a non-Hermitian effective theory for a repulsively interacting Fermi gas in the excited branch. The on-shell $T$-matrix is employed as a complex-valued interaction term, which describes a repulsive interaction between atoms in the excited branch and a two-body inelastic decay to the attractive branch. To see the feature of this model, we have addressed, in the weak coupling regime, the excitation properties of a repulsive Fermi polaron as well as the time-dependent number density. The analytic expressions obtained for these quantities qualitatively show a good agreement with recent experiments. By calculating the dynamical transverse spin susceptibility in the random phase approximation, we show that a ferromagnetic system with nonzero polarization undergoes a dynamical instability and tends towards a heterogeneous phase.
{"title":"Non-Hermitian Ferromagnetism in an Ultracold Fermi Gas","authors":"H. Tajima, K. Iida","doi":"10.7566/JPSJ.90.024004","DOIUrl":"https://doi.org/10.7566/JPSJ.90.024004","url":null,"abstract":"We develop a non-Hermitian effective theory for a repulsively interacting Fermi gas in the excited branch. The on-shell $T$-matrix is employed as a complex-valued interaction term, which describes a repulsive interaction between atoms in the excited branch and a two-body inelastic decay to the attractive branch. To see the feature of this model, we have addressed, in the weak coupling regime, the excitation properties of a repulsive Fermi polaron as well as the time-dependent number density. The analytic expressions obtained for these quantities qualitatively show a good agreement with recent experiments. By calculating the dynamical transverse spin susceptibility in the random phase approximation, we show that a ferromagnetic system with nonzero polarization undergoes a dynamical instability and tends towards a heterogeneous phase.","PeriodicalId":8838,"journal":{"name":"arXiv: Quantum Gases","volume":"71 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91514226","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-04-07DOI: 10.1103/PHYSREVRESEARCH.2.033478
David Viedma, M. Modugno
We compare the exact evolution of an expanding three-dimensional Bose-Einstein condensate with the evolution obtained from the effective scaling approach introduced in Ref. [1]. This approach, which consists in looking for self-similar solutions to be satisfied on average, is tested here in different geometries and configurations. We find that, in case of almost isotropic traps, the effective scaling reproduces with high accuracy the exact evolution dictated by the Gross-Pitaevskii equation for arbitrary values of the interactions, in agreement with the proof-of-concept of Ref. [2]. Conversely, it is shown that the hypothesis of universal self-similarity breaks down in case of strong anisotropies and trapped geometries.
{"title":"Effective self-similar expansion of a Bose-Einstein condensate: Free space versus confined geometries","authors":"David Viedma, M. Modugno","doi":"10.1103/PHYSREVRESEARCH.2.033478","DOIUrl":"https://doi.org/10.1103/PHYSREVRESEARCH.2.033478","url":null,"abstract":"We compare the exact evolution of an expanding three-dimensional Bose-Einstein condensate with the evolution obtained from the effective scaling approach introduced in Ref. [1]. This approach, which consists in looking for self-similar solutions to be satisfied on average, is tested here in different geometries and configurations. We find that, in case of almost isotropic traps, the effective scaling reproduces with high accuracy the exact evolution dictated by the Gross-Pitaevskii equation for arbitrary values of the interactions, in agreement with the proof-of-concept of Ref. [2]. Conversely, it is shown that the hypothesis of universal self-similarity breaks down in case of strong anisotropies and trapped geometries.","PeriodicalId":8838,"journal":{"name":"arXiv: Quantum Gases","volume":"60 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81634362","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-03-31DOI: 10.1103/PHYSREVRESEARCH.2.033453
G. Valent'i-Rojas, N. Westerberg, P. Öhberg
Topological field theories emerge at low energy in strongly-correlated condensed matter systems and appear in the context of planar gravity. In particular, the study of Chern-Simons terms gives rise to the concept of flux attachment when the gauge field is coupled to matter, yielding flux-charge composites. Here we investigate the generation of flux attachment in a Bose-Einstein condensate in the presence of non-linear synthetic gauge potentials. In doing so, we identify the U(1) Chern-Simons gauge field as a singular density-dependent gauge potential, which in turn can be expressed as a Berry connection. We envisage a proof-of-concept scheme where the artificial gauge field is perturbatively induced by an effective light-matter detuning created by interparticle interactions. At a mean field level, we recover the action of a "charged" superfluid minimally coupled to both a background and a Chern-Simons gauge field. Remarkably, a localised density perturbation in combination with a non-linear gauge potential gives rise to an effective composite boson model of fractional quantum Hall effect, displaying anyonic vortices.
{"title":"Synthetic flux attachment","authors":"G. Valent'i-Rojas, N. Westerberg, P. Öhberg","doi":"10.1103/PHYSREVRESEARCH.2.033453","DOIUrl":"https://doi.org/10.1103/PHYSREVRESEARCH.2.033453","url":null,"abstract":"Topological field theories emerge at low energy in strongly-correlated condensed matter systems and appear in the context of planar gravity. In particular, the study of Chern-Simons terms gives rise to the concept of flux attachment when the gauge field is coupled to matter, yielding flux-charge composites. Here we investigate the generation of flux attachment in a Bose-Einstein condensate in the presence of non-linear synthetic gauge potentials. In doing so, we identify the U(1) Chern-Simons gauge field as a singular density-dependent gauge potential, which in turn can be expressed as a Berry connection. We envisage a proof-of-concept scheme where the artificial gauge field is perturbatively induced by an effective light-matter detuning created by interparticle interactions. At a mean field level, we recover the action of a \"charged\" superfluid minimally coupled to both a background and a Chern-Simons gauge field. Remarkably, a localised density perturbation in combination with a non-linear gauge potential gives rise to an effective composite boson model of fractional quantum Hall effect, displaying anyonic vortices.","PeriodicalId":8838,"journal":{"name":"arXiv: Quantum Gases","volume":"60 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81611005","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-03-27DOI: 10.1103/PHYSREVA.103.013309
K. Lelas, O. Čelan, David Prelogovi'c, H. Buljan, D. Juki'c
We theoretically investigate the phenomenon of modulation instability for systems obeying nonlinear Schrodinger equation, which are under the influence of an external homogeneous synthetic magnetic field. For an initial condition, the instability is detected numerically by comparing dynamics with and without a small initial perturbation; the perturbations are characterized in a standard fashion by wavevectors in momentum space. We demonstrate that the region of (in)stability in momentum space, as well as time-evolution in real space, for identical initial conditions, depend on the choice of the gauge (i.e., vector potential) used to describe the homogeneous synthetic magnetic field. This superficially appears as if the gauge invariance is broken, but this is not true. When the system is evolved from an identical initial condition in two different gauges, it is equivalent to suddenly turning on the synthetic magnetic field at $t=0$. This gives rise, via Faraday's law, to an initial instantaneous kick of a synthetic electric field to the wavepacket, which can differ for gauges yielding an identical uniform magnetic field at $t>0$.
{"title":"Modulation instability in the nonlinear Schrödinger equation with a synthetic magnetic field: Gauge matters","authors":"K. Lelas, O. Čelan, David Prelogovi'c, H. Buljan, D. Juki'c","doi":"10.1103/PHYSREVA.103.013309","DOIUrl":"https://doi.org/10.1103/PHYSREVA.103.013309","url":null,"abstract":"We theoretically investigate the phenomenon of modulation instability for systems obeying nonlinear Schrodinger equation, which are under the influence of an external homogeneous synthetic magnetic field. For an initial condition, the instability is detected numerically by comparing dynamics with and without a small initial perturbation; the perturbations are characterized in a standard fashion by wavevectors in momentum space. We demonstrate that the region of (in)stability in momentum space, as well as time-evolution in real space, for identical initial conditions, depend on the choice of the gauge (i.e., vector potential) used to describe the homogeneous synthetic magnetic field. This superficially appears as if the gauge invariance is broken, but this is not true. When the system is evolved from an identical initial condition in two different gauges, it is equivalent to suddenly turning on the synthetic magnetic field at $t=0$. This gives rise, via Faraday's law, to an initial instantaneous kick of a synthetic electric field to the wavepacket, which can differ for gauges yielding an identical uniform magnetic field at $t>0$.","PeriodicalId":8838,"journal":{"name":"arXiv: Quantum Gases","volume":"40 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72605201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-03-26DOI: 10.1103/physreva.102.061301
Xiaoling Cui
We revisit the polaron-molecule transition in three-dimensional(3D) fermion systems using the well-established variational approach. The molecule is found to be intrinsically unstable against lowest-order particle-hole excitations, and it can only approximate the ground state of impurity system with finite total momentum in the strong coupling regime. The polaron-molecule transition can therefore be reinterpreted as a first-order transition between single impurity systems with different total momenta. Within certain interaction window near their transition, both states appear as local minima in the dispersion curve, indicating they can coexist in a realistic system. We have further confirmed the polaron-molecule coexistence in the presence of a finite impurity concentration and at low temperature, which directly leads to a smooth polaron-molecule transition as observed in recent experiments of 3D ultracold Fermi gases. Our results have provided an unambiguous physical picture for the competition and conversion between polaron and molecule, and also shed light on Fermi polaron properties in low dimensions.
{"title":"Fermi polaron revisited: Polaron-molecule transition and coexistence","authors":"Xiaoling Cui","doi":"10.1103/physreva.102.061301","DOIUrl":"https://doi.org/10.1103/physreva.102.061301","url":null,"abstract":"We revisit the polaron-molecule transition in three-dimensional(3D) fermion systems using the well-established variational approach. The molecule is found to be intrinsically unstable against lowest-order particle-hole excitations, and it can only approximate the ground state of impurity system with finite total momentum in the strong coupling regime. The polaron-molecule transition can therefore be reinterpreted as a first-order transition between single impurity systems with different total momenta. Within certain interaction window near their transition, both states appear as local minima in the dispersion curve, indicating they can coexist in a realistic system. We have further confirmed the polaron-molecule coexistence in the presence of a finite impurity concentration and at low temperature, which directly leads to a smooth polaron-molecule transition as observed in recent experiments of 3D ultracold Fermi gases. Our results have provided an unambiguous physical picture for the competition and conversion between polaron and molecule, and also shed light on Fermi polaron properties in low dimensions.","PeriodicalId":8838,"journal":{"name":"arXiv: Quantum Gases","volume":"134 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72889312","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-03-25DOI: 10.1103/physrevb.102.201114
N. Stroev, N. Berloff
Strongly coupled light-matter systems can carry information over long distances and realize low threshold polariton lasing, condensation and superfluidity. These systems are highly non-equilibrium in nature, so constant nonzero fluxes manifest themselves even at the steady state and set by a complicated interplay between nonlinearity, dispersion, pumping, dissipation and interactions between the various constituents of the system. Predicting the flow velocities even for a simple drive configuration has been challenging and no analytical spatially nonuniform solutions to the system were previously known. Based on the mean-field governing equations of lasers or polariton condensates, we develop a theoretical approach for engineering and controlling the velocity profiles by manipulating the spatial pumping and dissipation in the system. We present analytically exact pumping and dissipation profiles that lead to a large variety of spatially periodic density and velocity profiles. Our approach opens the way to the controllable implementation of laser or polariton flows for ultra-fast information processing and integrated circuits.
{"title":"Managing the flow of liquid light","authors":"N. Stroev, N. Berloff","doi":"10.1103/physrevb.102.201114","DOIUrl":"https://doi.org/10.1103/physrevb.102.201114","url":null,"abstract":"Strongly coupled light-matter systems can carry information over long distances and realize low threshold polariton lasing, condensation and superfluidity. These systems are highly non-equilibrium in nature, so constant nonzero fluxes manifest themselves even at the steady state and set by a complicated interplay between nonlinearity, dispersion, pumping, dissipation and interactions between the various constituents of the system. Predicting the flow velocities even for a simple drive configuration has been challenging and no analytical spatially nonuniform solutions to the system were previously known. Based on the mean-field governing equations of lasers or polariton condensates, we develop a theoretical approach for engineering and controlling the velocity profiles by manipulating the spatial pumping and dissipation in the system. We present analytically exact pumping and dissipation profiles that lead to a large variety of spatially periodic density and velocity profiles. Our approach opens the way to the controllable implementation of laser or polariton flows for ultra-fast information processing and integrated circuits.","PeriodicalId":8838,"journal":{"name":"arXiv: Quantum Gases","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88832969","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-03-25DOI: 10.1103/PHYSREVRESEARCH.2.033385
J. M. Midtgaard, Zhigang Wu, N. Goldman, G. Bruun
Realising and probing topological superfluids is a key goal for fundamental science, with exciting technological promises. Here, we show that chiral $p_x+ip_y$ pairing in a two-dimensional topological superfluid can be detected through circular dichroism, namely, as a difference in the excitation rates induced by a clockwise and counter-clockwise circular drive. For weak pairing, this difference is to a very good approximation determined by the Chern number of the superfluid, whereas there is a non-topological contribution scaling as the superfluid gap squared that becomes signifiant for stronger pairing. This gives rise to a competition between the experimentally driven goal to maximise the critical temperature of the superfluid, and observing a signal given by the underlying topology. Using a combination of strong coupling Eliashberg and Berezinskii-Kosterlitz-Thouless theory, we analyse this tension for an atomic Bose-Fermi gas, which represents a promising platform for realising a chiral superfluid. We identify a wide range of system parameters where both the critical temperature is high and the topological contribution to the dichroic signal is dominant.
{"title":"Detecting chiral pairing and topological superfluidity using circular dichroism","authors":"J. M. Midtgaard, Zhigang Wu, N. Goldman, G. Bruun","doi":"10.1103/PHYSREVRESEARCH.2.033385","DOIUrl":"https://doi.org/10.1103/PHYSREVRESEARCH.2.033385","url":null,"abstract":"Realising and probing topological superfluids is a key goal for fundamental science, with exciting technological promises. Here, we show that chiral $p_x+ip_y$ pairing in a two-dimensional topological superfluid can be detected through circular dichroism, namely, as a difference in the excitation rates induced by a clockwise and counter-clockwise circular drive. For weak pairing, this difference is to a very good approximation determined by the Chern number of the superfluid, whereas there is a non-topological contribution scaling as the superfluid gap squared that becomes signifiant for stronger pairing. This gives rise to a competition between the experimentally driven goal to maximise the critical temperature of the superfluid, and observing a signal given by the underlying topology. Using a combination of strong coupling Eliashberg and Berezinskii-Kosterlitz-Thouless theory, we analyse this tension for an atomic Bose-Fermi gas, which represents a promising platform for realising a chiral superfluid. We identify a wide range of system parameters where both the critical temperature is high and the topological contribution to the dichroic signal is dominant.","PeriodicalId":8838,"journal":{"name":"arXiv: Quantum Gases","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87376263","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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