Yi Zhou's research while affiliated with Chinese Academy of Sciences and other places
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Publications (95)
Previous investigations have suggested that the simplest spin-orbital model on the simplest frustrated lattice can host a nematic quantum spin-orbital liquid state. Namely, the orbital degeneracy of the SU(4) Kugel-Khomskii model tends to enhance quantum fluctuations and stabilize a quantum spin-orbital liquid exhibiting stripy features on the tria...
The search of quantum spin liquid (QSL), an exotic magnetic state with strongly fluctuating and highly entangled spins down to zero temperature, is a main theme in current condensed matter physics. However, there is no smoking gun evidence for deconfined spinons in any QSL candidate so far. The disorders and competing exchange interactions may prev...
A family of two-dimensional (2D) spin-1/2 models have been constructed to realize Kitaev’s sixteen-fold way of anyon theories. Defining a one-dimensional (1D) path through all the lattice sites, and performing the Jordan-Wigner transformation with the help of the 1D path, we find that such a spin-1/2 model is equivalent to a model with \nu ν specie...
Starting from the Landau’s kinetic equation, we show that an electronic liquid in d = 2, 3 spatial dimensions depicted by a Landau type effective theory will become incompressible on condition that the Landau parameters satisfy either (i) $1+F_{1}^{s}/d=0$ or (ii) $F_{0}^{s}\rightarrow {}+\infty$. The condition (i) is the Pomeranchuk instability in...
Superconductivity in strongly correlated electrons can emerge out from a normal state that is beyond the Landau's Fermi liquid paradigm, often dubbed as "non-Fermi liquid". While the theory for non-Fermi liquid is still not yet conclusive, a recent study on the exactly-solvable Hatsugai-Kohomoto (HK) model has suggested a non-Fermi liquid ground st...
We show that spontaneous time-reversal-symmetry (TRS) breaking can naturally arise from the interplay between pair density wave (PDW) ordering at multiple momenta and nesting of Fermi surfaces (FSs). Concretely, we consider the PDW superconductivity on a hexagonal lattice with nested FS at 3/4 electron filling, which is related to a recently discov...
A family of two-dimensional (2D) spin-1/2 models have been constructed to realize Kitaev's sixteen-fold way of anyon theories. Defining a one-dimensional (1D) path through all the lattice sites, and performing the Jordan-Wigner transformation with the help of the 1D path, we find that such a spin-1/2 model is equivalent to a model with $\nu$ specie...
Superconductivity in strongly correlated electrons can emerge out from a normal state that is beyond the Landau's Fermi liquid paradigm, often dubbed as ``non-Fermi liquid". While the theory for non-Fermi liquid is still not yet conclusive, a recent study on the exactly-solvable Hatsugai-Kohomoto (HK) model has suggested a non-Fermi liquid ground s...
The recent discovery of superconductivity at the interfaces between KTaO 3 and EuO (or LaAlO 3 ) gives birth to the second generation of oxide interface superconductors. This superconductivity exhibits a strong dependence on the surface plane of KTaO 3 , in contrast to the seminal LaAlO 3 /SrTiO 3 interface, and the superconducting transition tempe...
Starting from the Landau's kinetic equation, we show that an electronic liquid in $d=2,3$ dimensions depicted by a Landau type effective theory will become incompressible on condition that the Landau parameters satisfy either (i) $1+F_{1}^{s}/d=0$ or (ii) $F_{0}^{s}\to{}+\infty$. The condition (i) is the Pomeranchuk instability in the current chann...
We show that spontaneous time-reversal-symmetry (TRS) breaking can naturally arise from the interplay between pair density wave (PDW) ordering at multiple momenta and nesting of Fermi surfaces (FS). Concretely, we consider pair-density-wave superconductivity on a hexagonal lattice with nested FS at $3/4$ electron filling, which is related to a rece...
A sufficiently large parallel magnetic field will generate staggered supercurrent loops and a superfluid density wave in two weakly linked superconducting (SC) ultrathin films, resulting in an inhomogeneous Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state. The SC order parameter of such an FFLO state is characterized by Bloch wave functions, called th...
The nature of the ground state for the $S = 1/2$ kagome Heisenberg antiferromagnet (KHAF) has been elusive. We revisit this challenging problem and provide numerical evidence that its ground state might be a chiral spin liquid. Combining the density matrix renormalization group method and analytical analyses, we demonstrate that the previously obse...
The simplest spin-orbital model can host a nematic spin-orbital liquid state on the triangular lattice. We provide clear evidence that the ground state of the SU(4) Kugel-Khomskii model on the triangular lattice can be well described by a “single” Gutzwiller projected wave function with an emergent parton Fermi surface, despite it exhibits strong f...
We provide an efficient and accurate method for converting Hartree-Fock-Bogoliubov wave functions into matrix product states (MPSs). These wave functions, also known as Bogoliubov vacua, exhibit a peculiar entanglement structure that the eigenvectors of the reduced density matrix are also Bogoliubov vacua. We exploit this important feature to obtai...
Interfacial superconductivity has manifested itself in various types of heterostructures: band insulator–band insulator, band insulator–Mott insulator, and Mott insulator–metal. We report the observation of high-temperature superconductivity (HTS) in a complementary and long-expected type of heterostructures, which consists of two Mott insulators,...
The recent observation of superconductivity at the interfaces between KTaO3 and EuO (or LaAlO3) offers a new example of emergent phenomena at oxide interfaces. This superconductivity exhibits an unusual strong dependence on the crystalline orientation of KTaO3 and its superconducting transition temperature Tc is nearly one order of magnitude higher...
A sufficiently large parallel magnetic field will generate staggered supercurrent loops and superfluid density wave in two weakly linked superconducting (SC) ultra-thin films, resulting in an inhomogeneous Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state. The SC order parameter of such an FFLO state is characterized by Bloch wave functions, dubbed as...
The search of quantum spin liquid (QSL), an exotic magnetic state with strongly-fluctuating and highly-entangled spins down to zero temperature, is a main theme in current condensed matter physics. However, there is no smoking-gun evidence for deconfined spinons in any QSL candidate so far. The disorders and competing exchange interactions may prev...
Interfacial superconductivity has manifested itself in various types of heterostructures: band insulator-band insulator, band insulator-Mott insulator, and Mott insulator-metal. We report the observation of high-temperature superconductivity (HTS) in a complementary and long expected type of heterostructures, which consists of two Mott insulators,...
We provide an efficient and accurate method for converting Hartree-Fock-Bogoliubov wave functions into matrix product states (MPSs). These wave functions, also known as "Bogoliubov vacua", exhibit a peculiar entanglement structure that the eigenvectors of the reduced density matrix are also Bogoliubov vacua. We exploit this important feature to obt...
We propose to boost the performance of the density matrix renormalization group (DMRG) in two dimensions by using Gutzwiller projected states as the initialization Ansatz. When the Gutzwiller projected state is properly chosen, the notorious “local minimum” issue in DMRG can be circumvented and the precision of DMRG can be improved by orders of mag...
By combining the density matrix renormalization group (DMRG) method with Gutzwiller projected wave functions, we provide clear evidence that the ground state of the SU(4) Kugel-Khomskii spin-orbital model on the triangular lattice is a critical stripy state. This state preserves SU(4) symmetry, but spontaneously breaks translational symmetry by dou...
Controlling interfacial superconductivity
The interface between the oxides LaAlO 3 and KTaO 3 (111) has been shown to superconduct at temperatures up to 2 Kelvin. Chen et al. show that this superconductivity can be controlled with electric fields. As they tuned the gating voltage, the researchers observed a dome-shaped variation of the superconduct...
We report on the observation of a Tc∼0.9 K superconductivity at the interface between LaAlO3 film and the 5d transition metal oxide KTaO3(110) single crystal. The interface shows a large anisotropy of the upper critical field, and its superconducting transition is consistent with a Berezinskii-Kosterlitz-Thouless transition. Both facts suggest that...
We report on the observation of a Tc ~0.9 K superconductivity at the interface between LaAlO3 film and the 5d transition-metal oxide KTaO3(110) single crystal. The interface shows a large anisotropy of the upper critical field, and its superconducting transition is consistent with a Berezinskii-Kosterlitz-Thouless transition. Both facts suggest tha...
We report on an extraordinary field effect of the superconducting LaAlO3/KTaO3(111) interface with Tc ~2 K. By applying a gate voltage (VG) across KTaO3, the interface can be continuously tuned from superconducting into insulating states, yielding a dome-shaped Tc-VG dependence. The electric gating has only a minor effect on carrier density as evid...
![FIG. 3. The relative energy deviations δE g [defined in Eq. (6)] versus...](profile/Hui-Ke-Jin/publication/344180317/figure/fig4/AS:11431281155752664@1683281562998/The-relative-energy-deviations-dE-g-defined-in-Eq-6-versus-number-of-sweeps-in-DMRG_Q320.jpg)
We propose to boost the performance of the density matrix renormalization group (DMRG) in two dimensions by using Gutzwiller projected states as the initialization ansatz. When the Gutzwiller projected state is properly chosen, the notorious "local minimum" issue in DMRG can be circumvented and the precision of DMRG can be improved by orders of mag...
Recent work by Wu et al. [arXiv:1910.11011] proposed a numerical method, so-called matrix product operator–matrix product state (MPO-MPS) method, by which several types of quantum many-body wave functions, in particular, the projected Fermi sea state, can be efficiently represented as a tensor network. In this paper, we generalize the MPO-MPS metho...
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Spontaneous symmetry breaking has been a paradigm to describe the phase transitions in condensed matter physics. In addition to the continuous electromagnetic gauge symmetry, an unconventional superconductor can break discrete symmetries simultaneously, such as time reversal and lattice rotational symmetry. In this work we report a characteristic i...
Motivated by recent experiments and density functional theory calculations on choloalite PbCuTe2O6, which possesses a Cu-based three-dimensional hyperkagome lattice, we propose and study a J1−J2−J3 antiferromagnetic Heisenberg model on a hyperkagome lattice. In the classical limit, possible ground states are analyzed by two triangle rules, i.e., th...
Recent work by Wu {\em et al.} [arXiv:1910.11011] proposed a numerical method, so called MPO-MPS method, by which several types of quantum many-body wave functions, in particular, the projected Fermi sea state, can be efficiently represented as a tensor network. In this paper, we generalize the MPO-MPS method to study Gutzwiller projected paired st...
We construct a class of exactly solvable generalized Kitaev spin-1/2 models in arbitrary dimensions, which is beyond the category of quantum compass models. The Jordan-Wigner transformation is employed to prove the exact solvability. An exactly solvable quantum spin-1/2 model can be mapped to a gas of free Majorana fermions coupled to static Z2 gau...
Motivated by recent experiments and density functional theory calculations on a choloalite PbCuTe$_2$O$_6$, which possesses a Cu-based three-dimensional hyperkagome lattice, we propose and study a $J_1$-$J_2$-$J_3$ antiferromagnetic Heisenberg model on a hyperkagome lattice. In the classical limit, possible ground states are analyzed by two triangl...
The largest allowed symmetry in a spin-1 quantum system is an SU(3) symmetry rather than the SO(3) spin rotation. In this work, we reveal some SU(2) symmetries as subgroups of SU(3) that, to the best of our knowledge, have not previously been recognized. Then, we construct SU(2) symmetric Hamiltonians and explore the ground-state phase diagram in a...
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Spontaneous symmetry breaking has been a paradigm to describe the phase transitions in condensed matter physics. In addition to the continuous electromagnetic gauge symmetry, an unconventional superconductor can break discrete symmetries simultaneously, such as time reversal and lattice rotational symmetry. In this work we report a characteristic i...
Recently the superconductor and topological semimetal PbTaSe$_2$ was experimentally found to exhibit surface-only lattice rotational symmetry breaking below $T_c$. We exploit the Ginzburg-Landau free energy and propose a microscopic two-channel model to study possible superconducting states on the surface of PbTaSe$_2$. We identify two types of top...
We propose an exactly solvable quantum spin-12 model with time reversal invariance on a two-dimensional brick-wall lattice, where each unit cell consists of three sites. We find that the ground states are algebraic quantum spin liquid states. The spinon excitations are gapless and the energy dispersion is linear around two Dirac points. The ground...
It was recently proposed that, due to a nontrivial three-dimensional spin-orbital entanglement, Sr$_2$RuO$_4$ may be a time-reversal invariant nematic $p$-wave superconductor with coexisting in-plane and out-of-plane pairings. Here we discuss various signatures of such a state if the out-of-plane pairing component is dominant. First, the enhancemen...
The allowed largest symmetry in a quantum spin-1 system is SU(3) rather than spin rotation SO(3). In this Letter, we reveal some SU(2) symmetries as subgroups of the SU(3), which was not recognized to the best of our knowledge. We construct two-body Hamiltonians where these SU(2) symmetries are respected, and explore the ground phase diagram accord...
We construct a class of exactly solvable generalized Kitaev spin-$1/2$ models in arbitrary dimensions, which is beyond the category of quantum compass models. The Jordan-Wigner transformation is employed to prove the exact solvability. An exactly solvable quantum spin-$1/2$ models can be mapped to a gas of free Majorana fermions coupled to static $...
We propose an exactly solvable quantum spin-1/2 model with time reversal invariance on a two dimensional brick-wall lattice, where each unit cell consists of three sites. We find that the ground states are algebraic quantum spin liquid states. The spinon excitations are gapless and the energy dispersion is linear around two Dirac points. The ground...
Sau, Lutchyn, Tewari and Das Sarma (SLTD) proposed a heterostructure consisting of a semiconducting thin film sandwiched between an s-wave superconductor and a magnetic insulator and showed possible Majorana zero mode. Here we study spin polarization of the vortex core states and spin selective Andreev reflection at the vortex center of the SLTD mo...
Transition-metal chalcogenides host various phases of matter, such as charge-density wave (CDW), superconductors, and topological insulators or semimetals. Superconductivity and its competition with CDW in low-dimensional compounds have attracted much interest and stimulated considerable research. Here we report pressure induced superconductivity i...
![The particle wavefunction 〈0|cjck0†|0〉\documentclass[12pt]{minimal}...](publication/322403092/figure/fig4/AS:960921312690193@1606112902340/The-particle-wavefunction-0cjck00documentclass12ptminimal-usepackageamsmath_Q320.jpg)
We study Kitaev model in one-dimension with open boundary condition by using exact analytic methods for non-interacting system at zero chemical potential as well as in the symmetric case of Δ = t, and by using density-matrix-renormalization-group method for interacting system with nearest neighbor repulsion interaction. We suggest and examine an ed...
We study interaction effect of quantum spin Hall state in InAs/GaSb quantum wells under an in-plane magnetic field by using the self-consistent mean field theory. We construct a phase diagram as a function of intra-layer and inter-layer interactions, and identify two novel phases, a charge/spin density wave phase and an exciton condensate phase. Th...
Majorana zero modes (MZMs) have been predicted to exist in a topological insulator (TI)/superconductor (SC) heterostructure. A recent spin-polarized scanning tunneling microscope (STM) experiment [Sun et al., Phys. Rev. Lett. 116, 257003 (2016)] has observed a spin-polarization dependence of the zero bias differential tunneling conductance at the c...
Kitaev chain model with nearest neighbor interaction U is solved exactly at the symmetry point $\Delta=t$ and chemical potential $\mu=0$ in open boundary condition. By applying two Jordan-Wigner transformations and a spin-rotation, such a symmetric interacting model is mapped to a non-interacting fermion model, which can be diagonalized exactly. Th...
Recently, several experiments have illustrated that metal surface electrons can be manipulated to form a two dimensional (2D) lattice by depositing a designer molecule lattice on metal surface. This offers a promising new technique to construct artificial 2D electron lattices. Here we theoretically propose a molecule lattice pattern to realize an a...
We study Kitaev model in one-dimension with open boundary condition by using exact analytic methods for non-interacting system in the half filled limit as well as in the symmetric case of $\Delta=t$, and by using density-matrix-renormalization-group method for interacting system with nearest neighbor repulsion. We show explicitly that the emergence...
This article is an introductory review on the physics of quantum spin liquid states (QSLs). Quantum magnetism is a fast evolving field, and recent developments show that the ground states and low energy physics of frustrated spin systems may develop lot of exotic behaviors once we get out of the regime of semi-classical approaches. The aim of this...
Majorana zero modes (MZMs) have been predicted to exist in the topological insulator (TI)/superconductor (SC) heterostructure. Recent spin polarized scanning tunneling microscope (STM) experiment$^{1}$ has observed spin-polarization dependence of the zero bias differential tunneling conductance at the center of vortex core, which may be attributed...
Recently, theory has predicted a Majorana zero mode (MZM) to induce spin selective Andreev reflection (SSAR), a novel magnetic property which can be used to detect the MZM. Here, spin-polarized scanning tunneling microscopy or spectroscopy has been applied to probe SSAR of MZMs in a topological superconductor of the Bi2Te3/NbSe2 heterostructure. Th...
Motivated by the recent discovery of quantized spin Hall effect in InAs/GaSb quantum wells\cite{du2013}$^,$\cite{xu2014}, we theoretically study the effects of in-plane magnetic field and strain effect to the quantization of charge conductance by using Landauer-Butikker formalism. Our theory predicts a robustness of the conductance quantization aga...
The quantum spin Hall effect has been predicted theoretically and observed experimentally in InAs/GaSb quantum wells as a result of inverted band structures, for which electron bands in InAs layers are below heavy hole bands in GaSb layers in energy. The hybridization between electron bands and heavy hole bands leads to a hybridization gap away fro...
Motivated by recently discovered quasi-one-dimensional superconductor K$_{2}$Cr$_{3}$As$_{3}$ with $D_{3h}$ lattice symmetry, we study one-dimensional three-orbital Hubbard model with generic electron repulsive interaction described by intra-orbital repulsion $U$, inter-orbital repulsion, and Hund's coupling $J$. As extracted from density functiona...
Majorana fermion (MF) whose antiparticle is itself has been predicted in condensed matter systems. Signatures of the MFs have been reported as zero energy modes in various systems. More definitive evidences are highly desired to verify the existence of the MF. Very recently, theory has predicted MFs to induce spin selective Andreev reflection (SSAR...
We utilize variational method to study the Kondo screening of a spin-$1/2$
magnetic impurity in a three-dimensional (3D) Weyl semimetal with two Weyl
nodes along the $k_z$-axis. The model reduces to 3D Dirac semimetal when the
separation of the two Weyl nodes vanishes. When the chemical potential lies at
Dirac point, $\mu=0$, the impurity spin is s...
We study $S=1$ spin liquid states on the Kagome lattice constructed by
Gutzwiller projected $p_x+ip_y$ superconductors. Depending on the topology of
the fermions, the obtained spin liquids can be either non-Abelian or Abelian.
By calculating the modular matrices $S$ and $T$, we confirm that projected
topological superconductors are non-Abelian chir...
Non-centrosymmetric transition metal monopnictides are promising Weyl
semimetals (WSMs) with exotic physical properties. Although chiral WSM states
have been observed in TaAs and NbAs, there is no conclusive evidence on the
existence of Weyl fermions in NbP. Here, we use angle dependent quantum
oscillations to reveal that NbP has four pairs of unus...
We propose an extended Hubbard model with three molecular orbitals on a
hexagonal lattice with $D_{3h}$ symmetry to study recently discovered
superconductivity in A$_2$Cr$_3$As$_3$ (A=K,Rb,Cs). Effective
pairinginteractions $V(\mathbf{k},\mathbf{k^{\prime}})$ from paramagnon
fluctuations are derived within the random phase approximation, and are fo...
We propose that constructing a molecule super-lattice on a superconducting
ultrathin film is a promising way to manipulate superconductivity in
experiment. We theoretically study superconductivity in a molecule graphene
system, which is built by fabricating a hexagonal molecule super-lattice on
2-dimensional electron gas. The super-lattice potentia...
In a previous paper (Liu et al 2012 Phys. Rev. B 85 195144), a variational Monte Carlo method (based on Gutzwiller projected states) was generalized to S = 1 systems. This method provided very good trial ground states for the gapped phases of an S = 1 bilinear-biquadratic (BLBQ) Heisenberg chain. In this paper, we extend the approach to study the l...
Layered antiferromagnetic spin density wave (LAF) state is one of the
plausible ground states of charge neutral Bernal stacked bilayer graphene. In
this paper, we use determinant quantum Monte Carlo method to study the effect
of the electric field on the magnetic order in bilayer Hubbard model on a
honeycomb lattice. Our results qualitatively suppo...
Charge neutral bilayer graphene has a gapped ground state as transport experiments demonstrate. One of the plausible such ground states is layered antiferromagnetic spin density wave (LAF) state, where the spins in top and bottom layers have same magnitude with opposite directions. We propose that lightly charged bilayer graphene in an electric fie...
We study localized in-gap states and quantum spin Hall effect in Si-doped
InAs/GaSb quantum wells. We propose a model describing donor and/or acceptor
impurities to describe Si dopants. This model shows in-gap bound states and
wide conductance plateau with the quantized value $2e^2/h$ in light dopant
concentration, consistent with recent experiment...
In this paper we study the bond distortion effect on the electric polarization in spiral multiferroic magnets based on cluster and chain models. The bond distortion breaks the inversion symmetry and modifies the d-p hybridization. Consequently, it will affect the electric polarization, which can be divided into the spin-current part and the lattice...
We study in this paper quantum spin liquid states (QSLs) at the vicinity of
metal-insulator transition. Assuming that the low energy excitations in the
QSLs are labeled by "spinon" occupation numbers with the same Fermi surface
structure as in the corresponding metal (Fermi-liquid) side, we propose a
phenomenological Landau-like low energy theory f...
We study in this paper a series of Gutzwiller projected wave functions for S=1 spin chains obtained from a fermionic mean-field theory for general S>1/2 spin systems [ Liu, Zhou and Ng Phys. Rev. B 81 224417 (2010)] applied to the bilinear-biquadratic (J-K) model. The free-fermion mean-field states before the projection are 1D paring states. By com...
The two-dimensional Kane-Mele model with attractive Hubbard interaction U is studied by using a self-consistent mean-field theory. At U=0, the ground state is a topological insulator. At U larger than a critical value Uc, the ground state is a bulk superconductor. At 0<U<Uc, the bulk remains insulating while the edge state shows superconducting cor...
Recent transport experiments have demonstrated that the rhombohedral stacking
trilayer graphene is an insulator with an intrinsic gap of 6meV and the Bernal
stacking trilayer one is a metal. We propose a Hubbard model with a moderate
$U$ for layered graphene sheets, and show that the model well explains the
experiments of the stacking dependent ene...
The quantum spin Hall effect is predicted to be the result of two
oppositely polarized spin currents travelling in opposite directions
around the edges of a topological insulator. But only now has the spin
polarization of these currents been confirmed.
We study in this paper a series of Gutzwiller Projected wavefunctions for S=1
spin chains obtained from a fermionic mean-field theory for general S>1/2 spin
systems [Phys. Rev. B 81, 224417] applied to the bilinear-biquadratic (J-K)
model. The free-fermion mean field states before the projection are 1D paring
states. By comparing the energies and c...
The continuum limit of the tilted SU(2) spin model is shown to lead to a gauge Landau-Lifshitz equation which provides a unified description for various spin orders. For a definite gauge with zero field strength, we find a double periodic solution, where the conical spiral, in-plane spiral, helical, and ferromagnetic spin orders become special case...
Possible superconductivity in recently discovered (Tl,K)Fe$_x$Se$_2$
compounds is studied from the viewpoint of doped Mott insulator. The Mott
insulating phase is examined to be preferred in the parent compound at $x=1.5$
due to the presence of Fe vacancies. Partial filling of vacancies at the
Fe-sites introduces electron carriers and leads to elec...
Several experimental candidates for quantum spin liquids have been discovered in the past few years which appear to support gapless fermionic S=1/2 excitations called spinons. The spinons may form a Fermi sea coupled to a U(1) gauge field, and may undergo a pairing instability. We show that despite being charge neutral, the spinons couple to phonon...
We study mesoscopic spin Hall effect on the surface of a topological insulator with a step-function potential by using the McMillan method commonly used in the study of superconductor junctions. In the ballistic transport regime, we predict a giant spin polarization induced by a transverse electric current with parameter suitable to the topological...
In this paper, we study conically spiral multiferroic magnets with coupled magnetic and
ferroelectric orders. By generalizing the spin-current model, we study spin wave excitations
and electromagnons. We find that the electromagnon mode will split into two branches
with different dispersions in an (external or internal) magnetic field. We apply
our...
We have studied a quinary Fe-based superconductor Sr2VFeAsO3 by the measurements of x-ray diffraction, x-ray absorption, Mössbauer spectrum, resistivity, magnetization, and specific heat. This apparently undoped oxyarsenide is shown to be self-doped via electron transfer from the V3+ ions. We observed successive magnetic transitions within the VO2...
The fermion representation for S = 1/2 spins is generalized to spins with
arbitrary magnitudes. The symmetry properties of the representation is analyzed
where we find that the particle-hole symmetry in the spinon Hilbert space of S
=1/2 fermion representation is absent for S > 1/2. As a result, different path
integral representations and mean fiel...
We generalized the fermionic representation for Heisenberg model with spin-1/2 to arbitrary spin. The particle-hole symmetry for spin-1/2 Hilbert space is absent for S>=1. We find a Lagrangian for Heisenberg model with spin-1 or spin-3/2 with restored particle-hole symmetry and study the corresponding mean fields. The excitation spectrum is gapped...
In this paper we generalize the fermionic representation for $S=1/2$ spins to arbitrary spins. Within a mean field theory we obtain several spin liquid states for spin $S=1$ antiferromagnets on triangular lattices, including gapless f-wave spin liquid and topologically nontrivial $p_x+ip_y$ spin liquid. After considering different competing orders,...
Superconductivity in iron pnictides is studied by using a two-orbital Hubbard model in the large U limit. The Coulomb repulsion induces an orbital-dependent pairing between charge carriers. The pairing is found mainly from
the scattering within the same Fermi pocket where usually one single orbital dominates. The inter-pocket pair scatterings
deter...
We report an optical and atomic force microscopic (AFM) study of interactions between weakly charged silica spheres at a water-air interface. Attractive interactions are observed at intermediate interparticle distances and the amplitude of the attraction increases with the amount of salt (NaCl) added into the water phase. AFM images obtained in the...
Superconductivity in iron pnictides is studied by using a two-orbital Hubbard model in the large U limit. The Coulomb repulsion induces an orbital-dependent pairing between charge carriers. The pairing is found mainly from the scattering within the same Fermi pocket. The interpocket pair scatterings determine the symmetry of the superconductivity,...
In connection with recent discussion of topological order and topological
phase transitions in quantum systems, we reexamine circumstances that lead to
the appearance of a topological glass in certain classical lattice spin models.
Local bonding enforces constraints on low energy states which organize
themselves into topologically distinct classes...
Spin liquid states for the spin-$\frac{1}{2}$ antiferromagnetic Heisenberg model on a hyperkagome lattice are studied. We classify and study flux states according to symmetries. Applying this model to ${\mathrm{Na}}_{4}{\mathrm{Ir}}_{3}{\mathrm{O}}_{8}$, we propose that the high temperature state may be described by a spinon Fermi surface, which fo...
We examine the spin-triplet superconducting state of even parity mediated by ferromagnetic Hund's coupling between electrons in two almost degenerate orbital bands. This state may be realized in the recently discovered LaFeAsO(1-x)F(x). It is robust against orbital-independent disorder. The splitting of the orbital degeneracy suppresses superconduc...
We use group theory to classify the superconducting states of systems with two orbitals on a tetragonal lattice. The orbital part of the superconducting gap function can be either symmetric or antisymmetric. For the orbital symmetric state, the parity is even for spin singlet and odd for spin triplet; for the orbital antisymmetric state, the parity...
We study in this paper a non-equilibrium Fermi-edge problem where the system
under investigation is a single electron reservoir putting under an AC electric
field. We show that the electron Green's function and other correlation
functions in the problem can be solved and expressed exactly in terms of a
well-defined integral. The qualitative behavio...
We present a comment to a recent paper by Dominguez et. al. They claimed that the electrostatic interaction between charged colloids trapped at an interface formed by a dielectric and a screening phase is always isotropic to order $d^-3$. Base on this result, they claimed that in-plane dipolar attraction of order $d^-3$ between colloids cannot exis...
The nature of electrostatic interaction between like-charged particles at water-air interface is analyzed in this paper. We show that long-ranged electrostatic dipolar attraction between these objects generally exists. Our result provides a natural mechanism to explain the experimental observations of attraction between like-charge species trapped...
We study attractions between charged colloidal spheres in a solution and at a water-air interface. Both intrinsic inhomogeneous charge distribution and induced charge fluctuations may result in like-charge attraction. The intrinsic inhomogeneous charge distribution comes from the inhomogeneous surfaces of colloidal spheres, characterized by the num...
Citations
... In previous studies of the SU(2) symmetric case, a quantum spin liquid (of debated nature) was found between a 120 • and a stripe magnetic phase when J is increased [27,28,30,34,35]. In the SU(4) limit, there is evidence for a transition from a quantum liquid to four-sublattice magnetic order upon increasing J [19,22,69,[72][73][74]. We show that one can tune between these two limits via an external field and determine the different GSs and their excitations in between. ...
![[object Object]](https://i1.rgstatic.net/ii/profile.image/11431281155733414-1683281272772_Q64/Hui-Ke-Jin.jpg)
... Over the last few decades, experimental search for QSLs has identified several candidate materials. Examples include κ-(BEDT-TTF Cu CN 2 2 3 ) ( ) [4], ZnCu 3 (OH) 6 Cl 2 [5], NaYbSe 2 [6][7][8], and NaYbS 2 [9]. Since the discovery of Kitaev model, the search for QSLs has expanded to potential physical realizations of the model. ...
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... Changing the Chern number results in 16 distinct types of topological orders determined by ν mod 16. Such 16-fold way constructions have been discussed in several solvable models recently [105][106][107][108]. Here we discuss a different approach using anyon condensation in multilayer systems. ...
... subject of debate. At őrst glance, the nesting mechanism [20,27,[41][42][43][44][45][46] appears natural, aligning perfectly with the fermiology of the pure kagome lattice and resulting in the widely experimentally conőrmed 2 × 2 modulation within the plane [8, 16, 26-29, 31, 47]. This nesting paradigm has also been employed to account for the reported unconventional character of the CDW [42,43,48,49]. ...
... Recently, the HK model has won wide attention owing to its special role in uncovering the electron correlation effect from a solvable perspective. Non-Fermi liquid and unconventional superconductor [18][19][20][21][22][23], Kondo physics [24][25][26] have been intensively studied via HK model. HK model has also been extended to topological physics including correlated Chern insulators and topological Mott insulators [27][28][29] phase-diagram Since HK interaction is local in k-space, arXiv:2406.04168v1 ...
... Yet the influence of electron-phonon coupling on charge transport is the subject of debate [21,29], and the extent of polaronic effects on the charge carriers remains unclear. Moreover, a similar low-density metallic state appears in a diverse group of materials systems [1,[30][31][32], including thin films and heterostructures [33][34][35][36]. It is thus of fundamental importance to obtain microscopic understanding. ...
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... As the field increases, an additional phase transition associated with a tricritical point is found instead of a dimensional crossover from 3D to 2D. These results are inconsistent with the critical field behavior of the layered superconductor with infinite layers [2,[15][16][17], but show similarities to bilayer superconductors [21,22] instead. In Refs. ...
... Possible experimental platforms to realize QSOL include Moiré systems [51][52][53]. Numerical evidences of QSOL have been reported in studies on various SU(4) Heisenberg models and Kugel-Khomskii models [51][52][53][54][55][56][57][58][59]. Moreover, generalizations of the Kitaev spin-1/2 model to Kugel-Khomskii type spin-orbital interactions have lead to various exactly solvable models with QSOL ground states [60][61][62][63][64][65][66][67]. ...
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... Second, to further investigate the transition between the KSL and kinetic FM phases, it would be desirable to develop a parton theory incorporating bosonic holons and fermionic spinons. In this context, such a theory could be the starting point for a self-consistent random phase approximation [81] or Gutzwiller-boosted DMRG [82][83][84][85] in order to study the ordering instabilities and spin excitation spectra. Third, in our real-time evolution results we could observe that the excitations of spin induce a (weak) response of charge, and vice versa. ...
... The discovery of interface superconductivity [11][12][13][14][15][16][17][18][19][20][21][22][23][24] provides a novel opportunity to address the relationship between superconductivity and carrier density from a unique perspective. More and more oxide heterostructures are found to host interface superconductivity, e.g., LaAlO 3 /SrTiO 3 11,12 , La 1.55 Sr 0.45 CuO 4 /La 2 CuO 4 [13][14][15] , CaCuO 2 /SrTiO 3 16 , Ba 0.8 Sr 0.2 TiO 3 /La 2 CuO 4 17 , La 2 CuO 4 /PrBa 2 Cu 3 O 7 18 , EuO/KTaO 3 19 , and LaAlO 3 /KTaO 3 [19][20][21] . ...
