Biological ion channels show that ultrafast ions and molecules transmission are in a quantum way of single molecular or ionic chain with a certain number of molecules or ions, and we define it as ＂quantum-confined su...Biological ion channels show that ultrafast ions and molecules transmission are in a quantum way of single molecular or ionic chain with a certain number of molecules or ions, and we define it as ＂quantum-confined superfluid＂ （QSF）. This ordered ultrafast flow in the confined channel can be considered as ＂quantum tunneling fluid effect＂ with a ＂tunneling distance＂, which is corresponding to the period of QSF. Recent research demonstrated that artificial biomimetic nanochannels also showed the phenomenon of QSF, such as ion and water channels. The introduction of QSF concept in the fields of chemistry and biology may create significant impact. As for chemistry, the QSF effect provides new ideas for accurate synthesis in organic, inorganic, polymer, etc. We believe the implementation of the idea of QSF will promote the development of QSF biochemistry, biophysics, bioinformatics and biomedical science.展开更多
We propose a process of quantum-confined ion superfluid (QISF),which is enthalpy-driven confined ordered fluid,to explain the transmission of nerve signals.The ultrafast Na^+ and K^+ ions transportation through all so...We propose a process of quantum-confined ion superfluid (QISF),which is enthalpy-driven confined ordered fluid,to explain the transmission of nerve signals.The ultrafast Na^+ and K^+ ions transportation through all sodium-potassium pump nanochannels simultaneously in the membrane is without energy loss,and leads to QISF wave along the neuronal axon,which acts as an information medium in the ultrafast nerve signal transmission.The QISF process will not only provide a new view point for a reasonable explanation of ultrafast signal transmission in the nerves and brain,but also challenge the theory of matter wave for ions,molecules and particles.展开更多
Density order is usually a consequence of the competition between long-range and short-range interactions.Here we report a density ordered superfluid emergent from a homogeneous Mott insulator due to the competition b...Density order is usually a consequence of the competition between long-range and short-range interactions.Here we report a density ordered superfluid emergent from a homogeneous Mott insulator due to the competition between frustrations and local interactions.This transition is found in a Bose–Hubbard model on a frustrated triangle lattice with an extra pairing term.Furthermore,we find a quantum phase transition between two different density ordered superfluids,which is beyond the Landau–Ginzburg(LG)paradigm.A U(1)symmetry is emergent at the critical point,while the symmetry in each density ordered superfluid is Z_(2)×Z_(3).We call the transition a‘shamrock transition’,due to its degenerate ground state in the parameter space being a shamrock-like curve rather than a circle in an LG-type transition.Effective low energy theories are established for the two transitions mentioned above and we find their resemblance and differences with clock models.展开更多
The Accelerator Driven Sub-critical(ADS)system is a strategic plan to solve the nuclear waste problem for nuclear power plants in China.High-energy particle accelerators and colliders contain long strings of supercond...The Accelerator Driven Sub-critical(ADS)system is a strategic plan to solve the nuclear waste problem for nuclear power plants in China.High-energy particle accelerators and colliders contain long strings of superconducting devices,superconducting radio frequency cavities,and magnets,which may require cooling by 2 K superfluid helium(HeliumⅡ).2 K superfluid helium cryogenic system has become a research hot spot in the field of superconducting accelerators.In this study,the ADS Injector-I 2 K cryogenic system is examined in detail.The cryogenic system scheme design,key equipment,and technology design,such as the 2 K Joule–Thomson(J–T)heat exchanger and cryomodules CM1+CM2 design,are examined,in addition to the commissioning and operation of the cryogenic system.The ADS Injector-I 2 K cryogenic system is the first 100 W superfluid helium system designed and built independently in China.The ADS proton beam reached 10 Me V at 10 m A in July 2016 and 10 Me V at 2 m A in continuous mode in January 2017 and has been operated reliably for over 15,000 h,proving that the design of ADS Injector-I 2 K cryogenic system,the key equipment,and technology research are reasonable,reliable,and meet the requirements.The research into key technologies provides valuable engineering experience that can be helpful for future projects such as CI-ADS(China Initiative Accelerator-Driven System),SHINE(Shanghai High Repetition Rate XFEL and Extreme Light Facility),PAPS(Platform of Advanced Photon Source Technology),and CEPC(Circular Electron-Positron Collider),thereby developing national expertise in the field of superfluid helium cryogenic systems.展开更多
We study the coexistence of antiferromagnetism and unconventional superconductivity on the Creutz lattice which shows strictly flat bands in the noninteracting regime.The famous renormalized mean-field theory is used ...We study the coexistence of antiferromagnetism and unconventional superconductivity on the Creutz lattice which shows strictly flat bands in the noninteracting regime.The famous renormalized mean-field theory is used to deal with strong electron-electron repulsive Hubbard interaction in the effective low-energy t-J model,the superfluid weight of the unconventional superconducting state has been calculated via the linear response theory.An unconventional superconducting state with both spin-singlet and staggered spin-triplet pairs emerges beyond a critical antiferromagnetic coupling interaction,while antiferromagnetism accompanies this state.The superconducting state with only spin-singlet pairs is dominant with paramagnetic phase.The A phase is analogous to the pseudogap phase,which shows that electrons go to form pairs but do not cause a supercurrent.We also show the superfluid behavior of the unconventional superconducting state and its critical temperature.It is proven directly that the flat band can effectively raise the critical temperature of superconductivity.It is implementable to simulate and control strongly-correlated electrons'behavior on the Creutz lattice in the ultracold atoms experiment or other artificial structures.Our results may help the understanding of the interplay between unconventional superconductivity and magnetism.展开更多
Using the attractive Hubbard model as an example,we theoretically investigate the gap function,superfluid density,and superconductivity(SC)transition temperature on the semiperiodic Penrose lattice.First,we clarify th...Using the attractive Hubbard model as an example,we theoretically investigate the gap function,superfluid density,and superconductivity(SC)transition temperature on the semiperiodic Penrose lattice.First,we clarify that the gap function,density of states,and superfluid density positively correlate to the extended degree of single-particle states around the Fermi energy.Second,we confirm that the paramagnetic component of the superfluid density does not decay to zero in the thermodynamic limit,which is completely diferent from periodic systems.Regardless of the scaling,the diference between diamagnetic and paramagnetic currents remains stable,consistent with recent experimental results showing that although the superfluid density is lower than that of a periodic system,the system has bulk SC.Third,we find that the superfluid density and SC transition temperature can be boosted with the increase in disorder strength,which should be general to quasicrystal but unusual to periodic systems,reflecting the interplay between the underlying geometry and disorder.展开更多
A theory employing the vortex shape of the electron was presented to resolve the enigma of the wave-particle duality. Conventions such as “particle” and “wave” were used to describe the behavior of quantum objects...A theory employing the vortex shape of the electron was presented to resolve the enigma of the wave-particle duality. Conventions such as “particle” and “wave” were used to describe the behavior of quantum objects such as electrons. A superfluid vacuum formed the base to describe the basic vortex structure and properties of the electron, whereas various formulations derived from hydrodynamic laws described the electron vortex circumference, radius, angular velocity and angular frequency, angular momentum (spin) and magnetic momentum. A vortex electron fully explained the associations between momentum and wave, and hydrodynamic laws were essential in deriving the energy and angular frequency of the electron. In general, an electron traveling in space possesses internal and external motions. To derive the angular frequency of its internal motion, the Compton wavelength was used to represent the length of one cycle of the internal motion that is equal to the circumference of the electron vortex. The angular frequency of the electron vortex was calculated to obtain the same value according to Planck’s theory. A traveling vortex electron has internal and external motions that create a three-dimensional helix trajectory. The magnitude of the instantaneous velocity of the electron is the resultant of its internal and external velocities, being equal to the internal velocity reduced by the Lorentz factor (whose essence is presented in a detailed formulation). The wavelength of the helix trajectory represents the distance traveled by a particle along its axis during one period of revolution around the axis, resulting in the same de Broglie wavelength that corresponds to the helix pitch of the helix. Mathematical formulations were presented to demonstrate the relation between the energy of the vortex and its angular frequency and de Broglie’s wavelength;furthermore, Compton’s and de Broglie’s wavelengths were also differentiated.展开更多
A helium cryogenic system is designed by the Institute of Modern Physics,Chinese Academy of Sciences,to supply different cooling powers to the cryomodules of ion-Linac(iLinac)accelerator,which serves as the injector o...A helium cryogenic system is designed by the Institute of Modern Physics,Chinese Academy of Sciences,to supply different cooling powers to the cryomodules of ion-Linac(iLinac)accelerator,which serves as the injector of the High Intensity Heavy-Ion Accelerator Facility project.The iLinac is a superconducting heavy-ion accelerator approximately 100 m long and contains 13 cryomodules cooled by superfluid helium.This article describes the cryogenic system design of the iLinac accelerator.The requirements of the cryogenic system,such as cooling mode,refrigeration temperature,operating pressure and pressure stability,are introduced and described in detail.In addition,heat loads from different sources are analyzed and calculated quantitatively.An equivalent cooling capacity of 10 kW at 4.5 K was determined for the cryogenic system according to the total heat load.Furthermore,a system process design was conducted and analyzed in detail.Further,the system layout and the main equipment are presented.展开更多
Band mapping is widely used in various scenarios of cold atom physics to measure the quasi-momentum distribution and band population.However,conventional methods fail in strongly interacting systems.Here we propose an...Band mapping is widely used in various scenarios of cold atom physics to measure the quasi-momentum distribution and band population.However,conventional methods fail in strongly interacting systems.Here we propose and experimentally realize a novel scheme of band mapping that can accurately measure the quasi-momentum of interacting manybody systems.Through an anisotropic control in turning down the threedimensional optical lattice,we can eliminate the effect of interactions on the band mapping process.Then,based on a precise measurement of the quasi-momentum distribution,we introduce the incoherent fraction as a physical quantity that can quantify the degree of incoherence of quantum many-body states.This method enables precise measurement of processes such as the superfluid to Mott insulator phase transition.Additionally,by analyzing the spatial correlation derived from the quasi-momentum of superfluid-Mott insulator phase transitions,we obtain results consistent with the incoherent fraction.Our scheme broadens the scope of band mapping and provides a method for studying quantum many-body problems.展开更多
Bloch electrons in multiorbital systems carry quantum geometric information characteristic of their wavevector-dependent interorbital mixing.The geometric nature impacts electromagnetic responses,and this effect carri...Bloch electrons in multiorbital systems carry quantum geometric information characteristic of their wavevector-dependent interorbital mixing.The geometric nature impacts electromagnetic responses,and this effect carries over to the superconducting state,which receives a geometric contribution to the superfluid weight.In this paper,we show that this contribution could become negative under certain appropriate circumstances.This may facilitate the stabilization of Cooper pairings with real space phase modulation,i.e.,the pair density wave order,as we demonstrate through two-orbital model Bogoliubov de-Gennes mean-field calculations.The quantum geometric effect therefore constitutes an intrinsic mechanism for the formation of such a novel phase of matter in the absence of external magnetic field.展开更多
We review some recent progresses on the study of ultracold Fermi gases with synthetic spin-orbit coupling.In particular,we focus on the pairing superfluidity in these systems at zero temperature.Recent studies have sh...We review some recent progresses on the study of ultracold Fermi gases with synthetic spin-orbit coupling.In particular,we focus on the pairing superfluidity in these systems at zero temperature.Recent studies have shown that different forms of spin-orbit coupling in various spatial dimensions can lead to a wealth of novel pairing superfluidity.A common theme of these variations is the emergence of new pairing mechanisms which are direct results of spin-orbit-coupling-modified single-particle dispersion spectra.As different configurations can give rise to single-particle dispersion spectra with drastic differences in symmetry,spin dependence and low-energy density of states,spin-orbit coupling is potentially a powerful tool of quantum control,which,when combined with other available control schemes in ultracold atomic gases,will enable us to engineer novel states of matter.展开更多
Resistances of grain junctions of bulk polycrystalline YBa_(2)Cu_(3)O_(7−δ)(YBCO) and DyBa_(2)Cu_(3)O_(7−δ)(DyBCO) superconductors have been extracted following(i)Ambegaokar‐Baratoff(AB)and(ii)de Gennes(dG)equation...Resistances of grain junctions of bulk polycrystalline YBa_(2)Cu_(3)O_(7−δ)(YBCO) and DyBa_(2)Cu_(3)O_(7−δ)(DyBCO) superconductors have been extracted following(i)Ambegaokar‐Baratoff(AB)and(ii)de Gennes(dG)equations.Current–voltage(IV)below the critical temperature(T_(c))has been used to extract transport critical current density(J_(c)).The variations of the junction resistances,(RN)with temperature(T)exhibit that below a critical value of the normalised superfluid density(NSD),junctions become very low resistive and exhibit metallicity.Dependence of this feature of RN on the energy gaps has also been explored.Weak scattering limit is found to be compatible with the maximum of RN(T)as is observed from the corresponding NSD.展开更多
We observe a superfluid λ transition in the P-V criticality of charged Ad S black holes,within a holographic extended thermodynamics that considers the variation of Newton’s constant G.We calculate the critical expo...We observe a superfluid λ transition in the P-V criticality of charged Ad S black holes,within a holographic extended thermodynamics that considers the variation of Newton’s constant G.We calculate the critical exponents and find that they coincide with those of a superfluid transition in liquid4He and the Bose-Einstein condensation of hard-sphere Bose gas.Moreover,the independence of entropy and thermodynamic volume in the holographic framework allows us to construct a well-defined Ruppeiner metric.The associated scalar curvature suggests that the black holes show similar microscopic interactions with the hard-sphere Bose gas,where the superfluid(condensed)phase is dominated by repulsive interactions,while the normal(gas)phase is dominated by attractive interactions.These findings might provide us with new insights into the quantum aspect of charged Ad S black holes.展开更多
We theoretically investigate a three-dimensional Fermi gas with Rashba spin-orbit coupling in the presence of both out-of-plane and in-plane Zeeman fields. We show that, driven by a sufficiently large Zeeman field, ei...We theoretically investigate a three-dimensional Fermi gas with Rashba spin-orbit coupling in the presence of both out-of-plane and in-plane Zeeman fields. We show that, driven by a sufficiently large Zeeman field, either out-of-plane or in-plane, the superfluid phase of this system exhibits a number of interesting features, including inhomogeneous Fulde- Ferrell pairing, gapped or gapless topological order, and exotic quasi-particle excitations known as Weyl fermions that have linear energy dispersions in momentum space （i.e., massless Dirac fermions）. The topological superfluid phase can have either four or two topologically protected Weyl nodes. We present the phase diagrams at both zero and finite temperatures and discuss the possibility of their observation in an atomic Fermi gas with synthetic spin-orbit coupling. In this context, topological superfluid phase with an imperfect Rashba spin-orbit coupling is also studied.展开更多
Experiments show that the liquid helium-4 has either superfluid phase or solid phase when tem- perature decreases or the pressure of the system changes. In this paper, we discuss the equations which govern these phase...Experiments show that the liquid helium-4 has either superfluid phase or solid phase when tem- perature decreases or the pressure of the system changes. In this paper, we discuss the equations which govern these phase transitions and derive the criterions for these phase changes. Meanwhile, we give related approxi- mate solutions and draw the phase diagram. In addition, we also prove that the liquid helium-4 bifurcates from the trivial solution to an attractor as parameters cross certain critical value. The topological structure of the bifurcated attractor is also illustrated.展开更多
The superfluidity of helium-4 is explained until today by a quantum theory: the Bose-Einstein condensation. This theory is rather satisfactory in describing the superfluid state of helium-4 because this one is a syste...The superfluidity of helium-4 is explained until today by a quantum theory: the Bose-Einstein condensation. This theory is rather satisfactory in describing the superfluid state of helium-4 because this one is a system made up of bosons (particles of integer spin). However, the discovery of the superfluidity of helium-3 in 1971 called into question the veracity of this quantum theory. In fact, helium-3 being a system composed of fermions (particles of half-integer spin), it cannot be subject to Bose-Einstein condensation. It is to correct this deficiency that we introduce here a classical (non-quantum) theory of superfluids. This new theory makes no difference between the λ transition of bosons and that of fermions. It is based on a fundamental law: “in a superfluid, density is conserved”. In this work, we have shown that this simple law explains not only the zero viscosity of superfluids but also the surprising phenomena observed in the superfluid state, I quote the liquidity of helium at normal pressure down to 0 K, vaporization without boiling, high thermal conductivity, the fountain effect, the ability to go up one side of the wall of a container to come down on the other side and the existence of a critical velocity.展开更多
The spin-orbit coupled lattice system under Zeeman fields provides an ideal platform to realize exotic pairing states. Notable examples range from the topological superfluid/superconducting （tSC） state, which is gap...The spin-orbit coupled lattice system under Zeeman fields provides an ideal platform to realize exotic pairing states. Notable examples range from the topological superfluid/superconducting （tSC） state, which is gapped in the bulk but metallic at the edge, to the Fulde-Ferrell （FF） state （having a phase-modulated order parameter with a uniform amplitude） and the Larkin-Ovchinnikov （LO） state （having a spatially varying order parameter amplitude）. Here, we show that the topological FF state with Chern number （C = -1） （tFF1） and topological LO state with C = 2 （tLO2） can be stabilized in Rashba spin-orbit coupled lattice systems in the presence of both in-plane and out-of-plane Zeeman fields. Besides the inhomogeneous tSC states, in the presence of a weak in-plane Zeeman field, two topological BCS phases may emerge with C = -1 （tBCS1） far from half fining and C = 2 （tBCS2） near half filling. We show intriguing effects such as different spatial profiles of order parameters for FF and LO states, the topological evolution among inhomogeneous tSC states, and different non-trivial Chern numbers for the tFF1 and tLO1,2 states, which are peculiar to the lattice system. Global phase diagrams for various topological phases are presented for both half-rifling and doped cases. The edge states as well as local density of states spectra are calculated for tSC states in a 2D strip.展开更多
基金supported by the National Key R&D Program of China(2017YFA0206900)the National Natural Science Foundation of China(21625303)
文摘Biological ion channels show that ultrafast ions and molecules transmission are in a quantum way of single molecular or ionic chain with a certain number of molecules or ions, and we define it as ＂quantum-confined superfluid＂ （QSF）. This ordered ultrafast flow in the confined channel can be considered as ＂quantum tunneling fluid effect＂ with a ＂tunneling distance＂, which is corresponding to the period of QSF. Recent research demonstrated that artificial biomimetic nanochannels also showed the phenomenon of QSF, such as ion and water channels. The introduction of QSF concept in the fields of chemistry and biology may create significant impact. As for chemistry, the QSF effect provides new ideas for accurate synthesis in organic, inorganic, polymer, etc. We believe the implementation of the idea of QSF will promote the development of QSF biochemistry, biophysics, bioinformatics and biomedical science.
基金the National Natural Science Foundation of China (Nos.51603211 and 51673107)the National Key R&D Program of China (No.2016YFA0200803)the 111 Project (No.B1 4009).
文摘We propose a process of quantum-confined ion superfluid (QISF),which is enthalpy-driven confined ordered fluid,to explain the transmission of nerve signals.The ultrafast Na^+ and K^+ ions transportation through all sodium-potassium pump nanochannels simultaneously in the membrane is without energy loss,and leads to QISF wave along the neuronal axon,which acts as an information medium in the ultrafast nerve signal transmission.The QISF process will not only provide a new view point for a reasonable explanation of ultrafast signal transmission in the nerves and brain,but also challenge the theory of matter wave for ions,molecules and particles.
基金supported by the Beijing Natural Science Foundation(Z180013)(YC)National Natural Science Foundation of China(NSFC)under Grant No.12174358(YC)and No.11734010(YC and CW)MOST Grant No.2016YFA0301600(CW)。
文摘Density order is usually a consequence of the competition between long-range and short-range interactions.Here we report a density ordered superfluid emergent from a homogeneous Mott insulator due to the competition between frustrations and local interactions.This transition is found in a Bose–Hubbard model on a frustrated triangle lattice with an extra pairing term.Furthermore,we find a quantum phase transition between two different density ordered superfluids,which is beyond the Landau–Ginzburg(LG)paradigm.A U(1)symmetry is emergent at the critical point,while the symmetry in each density ordered superfluid is Z_(2)×Z_(3).We call the transition a‘shamrock transition’,due to its degenerate ground state in the parameter space being a shamrock-like curve rather than a circle in an LG-type transition.Effective low energy theories are established for the two transitions mentioned above and we find their resemblance and differences with clock models.
文摘The Accelerator Driven Sub-critical(ADS)system is a strategic plan to solve the nuclear waste problem for nuclear power plants in China.High-energy particle accelerators and colliders contain long strings of superconducting devices,superconducting radio frequency cavities,and magnets,which may require cooling by 2 K superfluid helium(HeliumⅡ).2 K superfluid helium cryogenic system has become a research hot spot in the field of superconducting accelerators.In this study,the ADS Injector-I 2 K cryogenic system is examined in detail.The cryogenic system scheme design,key equipment,and technology design,such as the 2 K Joule–Thomson(J–T)heat exchanger and cryomodules CM1+CM2 design,are examined,in addition to the commissioning and operation of the cryogenic system.The ADS Injector-I 2 K cryogenic system is the first 100 W superfluid helium system designed and built independently in China.The ADS proton beam reached 10 Me V at 10 m A in July 2016 and 10 Me V at 2 m A in continuous mode in January 2017 and has been operated reliably for over 15,000 h,proving that the design of ADS Injector-I 2 K cryogenic system,the key equipment,and technology research are reasonable,reliable,and meet the requirements.The research into key technologies provides valuable engineering experience that can be helpful for future projects such as CI-ADS(China Initiative Accelerator-Driven System),SHINE(Shanghai High Repetition Rate XFEL and Extreme Light Facility),PAPS(Platform of Advanced Photon Source Technology),and CEPC(Circular Electron-Positron Collider),thereby developing national expertise in the field of superfluid helium cryogenic systems.
基金Project supported by the Natural Science Basic Research Program of Shaanxi(Program Nos.2023KJXX-064 and 2021JQ-748)the National Natural Science Foundation of China(Grant Nos.11804213 and 12174238)Scientific Research Foundation of Shaanxi University of Technology(Grant No.SLGRCQD2006).
文摘We study the coexistence of antiferromagnetism and unconventional superconductivity on the Creutz lattice which shows strictly flat bands in the noninteracting regime.The famous renormalized mean-field theory is used to deal with strong electron-electron repulsive Hubbard interaction in the effective low-energy t-J model,the superfluid weight of the unconventional superconducting state has been calculated via the linear response theory.An unconventional superconducting state with both spin-singlet and staggered spin-triplet pairs emerges beyond a critical antiferromagnetic coupling interaction,while antiferromagnetism accompanies this state.The superconducting state with only spin-singlet pairs is dominant with paramagnetic phase.The A phase is analogous to the pseudogap phase,which shows that electrons go to form pairs but do not cause a supercurrent.We also show the superfluid behavior of the unconventional superconducting state and its critical temperature.It is proven directly that the flat band can effectively raise the critical temperature of superconductivity.It is implementable to simulate and control strongly-correlated electrons'behavior on the Creutz lattice in the ultracold atoms experiment or other artificial structures.Our results may help the understanding of the interplay between unconventional superconductivity and magnetism.
基金supported by the National Natural Science Foundation of China(Grant Nos.12074031,12234016,12174024,11704029,and 11674025)。
文摘Using the attractive Hubbard model as an example,we theoretically investigate the gap function,superfluid density,and superconductivity(SC)transition temperature on the semiperiodic Penrose lattice.First,we clarify that the gap function,density of states,and superfluid density positively correlate to the extended degree of single-particle states around the Fermi energy.Second,we confirm that the paramagnetic component of the superfluid density does not decay to zero in the thermodynamic limit,which is completely diferent from periodic systems.Regardless of the scaling,the diference between diamagnetic and paramagnetic currents remains stable,consistent with recent experimental results showing that although the superfluid density is lower than that of a periodic system,the system has bulk SC.Third,we find that the superfluid density and SC transition temperature can be boosted with the increase in disorder strength,which should be general to quasicrystal but unusual to periodic systems,reflecting the interplay between the underlying geometry and disorder.
文摘A theory employing the vortex shape of the electron was presented to resolve the enigma of the wave-particle duality. Conventions such as “particle” and “wave” were used to describe the behavior of quantum objects such as electrons. A superfluid vacuum formed the base to describe the basic vortex structure and properties of the electron, whereas various formulations derived from hydrodynamic laws described the electron vortex circumference, radius, angular velocity and angular frequency, angular momentum (spin) and magnetic momentum. A vortex electron fully explained the associations between momentum and wave, and hydrodynamic laws were essential in deriving the energy and angular frequency of the electron. In general, an electron traveling in space possesses internal and external motions. To derive the angular frequency of its internal motion, the Compton wavelength was used to represent the length of one cycle of the internal motion that is equal to the circumference of the electron vortex. The angular frequency of the electron vortex was calculated to obtain the same value according to Planck’s theory. A traveling vortex electron has internal and external motions that create a three-dimensional helix trajectory. The magnitude of the instantaneous velocity of the electron is the resultant of its internal and external velocities, being equal to the internal velocity reduced by the Lorentz factor (whose essence is presented in a detailed formulation). The wavelength of the helix trajectory represents the distance traveled by a particle along its axis during one period of revolution around the axis, resulting in the same de Broglie wavelength that corresponds to the helix pitch of the helix. Mathematical formulations were presented to demonstrate the relation between the energy of the vortex and its angular frequency and de Broglie’s wavelength;furthermore, Compton’s and de Broglie’s wavelengths were also differentiated.
文摘A helium cryogenic system is designed by the Institute of Modern Physics,Chinese Academy of Sciences,to supply different cooling powers to the cryomodules of ion-Linac(iLinac)accelerator,which serves as the injector of the High Intensity Heavy-Ion Accelerator Facility project.The iLinac is a superconducting heavy-ion accelerator approximately 100 m long and contains 13 cryomodules cooled by superfluid helium.This article describes the cryogenic system design of the iLinac accelerator.The requirements of the cryogenic system,such as cooling mode,refrigeration temperature,operating pressure and pressure stability,are introduced and described in detail.In addition,heat loads from different sources are analyzed and calculated quantitatively.An equivalent cooling capacity of 10 kW at 4.5 K was determined for the cryogenic system according to the total heat load.Furthermore,a system process design was conducted and analyzed in detail.Further,the system layout and the main equipment are presented.
基金supported by the National Key Research and Development Program of China(No.2021YFA1400900).
文摘Band mapping is widely used in various scenarios of cold atom physics to measure the quasi-momentum distribution and band population.However,conventional methods fail in strongly interacting systems.Here we propose and experimentally realize a novel scheme of band mapping that can accurately measure the quasi-momentum of interacting manybody systems.Through an anisotropic control in turning down the threedimensional optical lattice,we can eliminate the effect of interactions on the band mapping process.Then,based on a precise measurement of the quasi-momentum distribution,we introduce the incoherent fraction as a physical quantity that can quantify the degree of incoherence of quantum many-body states.This method enables precise measurement of processes such as the superfluid to Mott insulator phase transition.Additionally,by analyzing the spatial correlation derived from the quasi-momentum of superfluid-Mott insulator phase transitions,we obtain results consistent with the incoherent fraction.Our scheme broadens the scope of band mapping and provides a method for studying quantum many-body problems.
基金supported by the National Natural Science Foundation of China(Grant No.11904155)the Guangdong Provincial Key Laboratory(Grant No.2019B121203002)+1 种基金the Guangdong Science and Technology Department(Grant No.2022A1515011948)the Shenzhen Science and Technology Program(Grant No.KQTD20200820113010023)。
文摘Bloch electrons in multiorbital systems carry quantum geometric information characteristic of their wavevector-dependent interorbital mixing.The geometric nature impacts electromagnetic responses,and this effect carries over to the superconducting state,which receives a geometric contribution to the superfluid weight.In this paper,we show that this contribution could become negative under certain appropriate circumstances.This may facilitate the stabilization of Cooper pairings with real space phase modulation,i.e.,the pair density wave order,as we demonstrate through two-orbital model Bogoliubov de-Gennes mean-field calculations.The quantum geometric effect therefore constitutes an intrinsic mechanism for the formation of such a novel phase of matter in the absence of external magnetic field.
基金supported by National Fundamental Research Program of China(Grant Nos.2011CB921200 and 2011CBA00200)National Key Basic Research Program(Grant No.2013CB922000)+4 种基金National Natural Science Foundation(Grant No.60921091)National Science Foundation of China(Grant Nos.10904172,11104158,11374177,11105134,1127409and 11374283)the Fundamental Research Funds for the Central Universities(Grant No.WK2470000006)the Research Funds of Renmin University of China(Grant No.10XNL016)the programs of Chinese Academy of Sciences
文摘We review some recent progresses on the study of ultracold Fermi gases with synthetic spin-orbit coupling.In particular,we focus on the pairing superfluidity in these systems at zero temperature.Recent studies have shown that different forms of spin-orbit coupling in various spatial dimensions can lead to a wealth of novel pairing superfluidity.A common theme of these variations is the emergence of new pairing mechanisms which are direct results of spin-orbit-coupling-modified single-particle dispersion spectra.As different configurations can give rise to single-particle dispersion spectra with drastic differences in symmetry,spin dependence and low-energy density of states,spin-orbit coupling is potentially a powerful tool of quantum control,which,when combined with other available control schemes in ultracold atomic gases,will enable us to engineer novel states of matter.
文摘Resistances of grain junctions of bulk polycrystalline YBa_(2)Cu_(3)O_(7−δ)(YBCO) and DyBa_(2)Cu_(3)O_(7−δ)(DyBCO) superconductors have been extracted following(i)Ambegaokar‐Baratoff(AB)and(ii)de Gennes(dG)equations.Current–voltage(IV)below the critical temperature(T_(c))has been used to extract transport critical current density(J_(c)).The variations of the junction resistances,(RN)with temperature(T)exhibit that below a critical value of the normalised superfluid density(NSD),junctions become very low resistive and exhibit metallicity.Dependence of this feature of RN on the energy gaps has also been explored.Weak scattering limit is found to be compatible with the maximum of RN(T)as is observed from the corresponding NSD.
基金supported by the National Natural Science Foundation of China(Grant Nos.12275183,12275184,12105191,and 12175212)。
文摘We observe a superfluid λ transition in the P-V criticality of charged Ad S black holes,within a holographic extended thermodynamics that considers the variation of Newton’s constant G.We calculate the critical exponents and find that they coincide with those of a superfluid transition in liquid4He and the Bose-Einstein condensation of hard-sphere Bose gas.Moreover,the independence of entropy and thermodynamic volume in the holographic framework allows us to construct a well-defined Ruppeiner metric.The associated scalar curvature suggests that the black holes show similar microscopic interactions with the hard-sphere Bose gas,where the superfluid(condensed)phase is dominated by repulsive interactions,while the normal(gas)phase is dominated by attractive interactions.These findings might provide us with new insights into the quantum aspect of charged Ad S black holes.
基金supported by the ARC Discovery Projects(Grant Nos.FT140100003,FT130100815,DP140103231,and DP140100637)the National Basic Research Program of China(Grant No.2011CB921502)+1 种基金the US National Science Foundationthe Welch Foundation(Grant No.C-1669)
文摘We theoretically investigate a three-dimensional Fermi gas with Rashba spin-orbit coupling in the presence of both out-of-plane and in-plane Zeeman fields. We show that, driven by a sufficiently large Zeeman field, either out-of-plane or in-plane, the superfluid phase of this system exhibits a number of interesting features, including inhomogeneous Fulde- Ferrell pairing, gapped or gapless topological order, and exotic quasi-particle excitations known as Weyl fermions that have linear energy dispersions in momentum space （i.e., massless Dirac fermions）. The topological superfluid phase can have either four or two topologically protected Weyl nodes. We present the phase diagrams at both zero and finite temperatures and discuss the possibility of their observation in an atomic Fermi gas with synthetic spin-orbit coupling. In this context, topological superfluid phase with an imperfect Rashba spin-orbit coupling is also studied.
文摘Experiments show that the liquid helium-4 has either superfluid phase or solid phase when tem- perature decreases or the pressure of the system changes. In this paper, we discuss the equations which govern these phase transitions and derive the criterions for these phase changes. Meanwhile, we give related approxi- mate solutions and draw the phase diagram. In addition, we also prove that the liquid helium-4 bifurcates from the trivial solution to an attractor as parameters cross certain critical value. The topological structure of the bifurcated attractor is also illustrated.
文摘The superfluidity of helium-4 is explained until today by a quantum theory: the Bose-Einstein condensation. This theory is rather satisfactory in describing the superfluid state of helium-4 because this one is a system made up of bosons (particles of integer spin). However, the discovery of the superfluidity of helium-3 in 1971 called into question the veracity of this quantum theory. In fact, helium-3 being a system composed of fermions (particles of half-integer spin), it cannot be subject to Bose-Einstein condensation. It is to correct this deficiency that we introduce here a classical (non-quantum) theory of superfluids. This new theory makes no difference between the λ transition of bosons and that of fermions. It is based on a fundamental law: “in a superfluid, density is conserved”. In this work, we have shown that this simple law explains not only the zero viscosity of superfluids but also the surprising phenomena observed in the superfluid state, I quote the liquidity of helium at normal pressure down to 0 K, vaporization without boiling, high thermal conductivity, the fountain effect, the ability to go up one side of the wall of a container to come down on the other side and the existence of a critical velocity.
基金We thank Y. S. Wu, R. B. Tao, T. K. Lee, and A. Varlamov for fruitful discussions. This work was supported by the State Key Programs of Chiaa （Grant Nos. 2017YFA0304204, and 2016YFA0300504） and the National Nat- ural Science Foundation of China （Grant Nos. 11625416 and 11474064）.
文摘The spin-orbit coupled lattice system under Zeeman fields provides an ideal platform to realize exotic pairing states. Notable examples range from the topological superfluid/superconducting （tSC） state, which is gapped in the bulk but metallic at the edge, to the Fulde-Ferrell （FF） state （having a phase-modulated order parameter with a uniform amplitude） and the Larkin-Ovchinnikov （LO） state （having a spatially varying order parameter amplitude）. Here, we show that the topological FF state with Chern number （C = -1） （tFF1） and topological LO state with C = 2 （tLO2） can be stabilized in Rashba spin-orbit coupled lattice systems in the presence of both in-plane and out-of-plane Zeeman fields. Besides the inhomogeneous tSC states, in the presence of a weak in-plane Zeeman field, two topological BCS phases may emerge with C = -1 （tBCS1） far from half fining and C = 2 （tBCS2） near half filling. We show intriguing effects such as different spatial profiles of order parameters for FF and LO states, the topological evolution among inhomogeneous tSC states, and different non-trivial Chern numbers for the tFF1 and tLO1,2 states, which are peculiar to the lattice system. Global phase diagrams for various topological phases are presented for both half-rifling and doped cases. The edge states as well as local density of states spectra are calculated for tSC states in a 2D strip.
