By imaginary-time evolution with the Hamiltonian, an arbitrary state arrives in the system's ground state. In this paper, we conjecture that this dynamics can be simulated by a measurement-only circuit (MOC), where each projective measurement is set in a suitable way. Based on terms in the Hamiltonian and ratios of their parameters (coefficients), we propose a guiding principle for the choice of the measured operators called “stabilizers” and also the probability of projective measurement in the MOC. In order to examine and verify this conjecture of the parameter ratio and probability ratio correspondence in a practical way, we study a generalized $(1+1)$-dimensional $Z_2$ lattice gauge Higgs model, whose phase diagram is very rich, including the symmetry-protected topological phase, deconfinement phase, etc. We find that the MOC constructed by the guiding principle reproduces the phase diagram in a very similar way to that of the ground state of the gauge Higgs Hamiltonian. The present paper indicates that the MOC can be broadly used to produce interesting phases of matter, which are difficult to be simulated by ordinary Hamiltonian systems composed of stabilizer-type terms.

The two-dimensional (2D) van der Waals ferromagnetic semiconductors, such as ${\mathrm{CrI}}_3$ and ${\mathrm{Cr}}_2{\mathrm{Ge}}_2{\mathrm{Te}}_6$, and the 2D ferromagnetic metals, such as ${\mathrm{Fe}}_3{\mathrm{GeTe}}_2$ and ${\mathrm{MnSe}}_2$, have been obtained in recent experiments and attracted a lot of attention. The superexchange interaction has been suggested to dominate the magnetic interactions in these 2D magnetic systems. In the usual theoretical studies, the expression of the 2D Heisenberg models were fixed by hand due to experiences. Here, we propose a procedure to determine the expression of the 2D Heisenberg models by counting the possible superexchange paths with the density functional theory and Wannier function calculations. With this method, we obtain a 2D Heisenberg model with six different nearest-neighbor exchange coupling constants for the 2D ferromagnetic metal ${\mathrm{Cr}}_3{\mathrm{Te}}_6$, which is very different for the crystal structure of Cr atoms in ${\mathrm{Cr}}_3{\mathrm{Te}}_6$. The calculated Curie temperature Tc = 328 K is close to the Tc = 344 K of 2D ${\mathrm{Cr}}_3{\mathrm{Te}}_6$ reported in recent experiment. In addition, we predict two stable 2D ferromagnetic semiconductors ${\mathrm{Cr}}_3{\mathrm{O}}_6$ and ${\mathrm{Mn}}_3{\mathrm{O}}_6$ sharing the same crystal structure of ${\mathrm{Cr}}_3{\mathrm{Te}}_6$. The similar Heisenberg models are obtained for 2D ${\mathrm{Cr}}_3{\mathrm{O}}_6$ and ${\mathrm{Mn}}_3{\mathrm{O}}_6$, where the calculated Tc is 218 K and 208 K, respectively. Our paper offers a practical approach to determine the expression of Heisenberg models for these 2D magnetic semiconductors and metals, and builds up a solid basis for further studies.

We consider the spin-$1/2$ Heisenberg chain with boundary magnetic fields and analyze it using a combination of Bethe ansatz and density matrix renormalization group (DMRG) techniques. We show that the system exhibits several different ground states, which depend on the orientation of the boundary magnetic fields. When both the boundary fields take equal values greater than a critical field strength, each edge in the ground state accumulates a fractional spin which saturates to spin $1/4$, which is similar to systems exhibiting symmetry protected topological phases (SPT). Unlike in SPT systems, the fractional boundary spin in the Heisenberg spin chain is not a genuine quantum number since the variance of the associated operator does not vanish, this is due to the absence of a bulk gap. The system exhibits high-energy bound states when the boundary fields take values greater than the critical field. All the excitations in the system can be sorted out into towers whose number depends on the number of bound states exhibited by the system. As the boundary fields are varied, in addition to the ground-state phase transition, we find that the system may undergo a boundary eigenstate phase transition (BEPT) where the number of towers of the Hilbert space changes. We further inquire how the EPT reflects itself on local ground-state properties by computing the magnetization profile $\langle S_j^z\rangle$ using DMRG. We identify a clear qualitative change from low edge fields to high edge fields when crossing the critical field. We though are unable to conclude on the basis of our data that EPT corresponds to a genuine phase transition in the ground state.

We study analytically, within a continuous field model, and numerically, on lattices containing ${10}^5$ spins, the integral absorption of microwaves by a random-anisotropy magnet, $\int d\omega P\left(\omega \right)$. It scales as $D_R^2/J$ on the random-anisotropy strength $D_R$ and the strength of the ferromagnetic exchange $J$ in low-anisotropy amorphous magnetic materials. At high anisotropy and in low-anisotropy materials sintered from sufficiently large ferromagnetic grains, the integral power scales linearly on $D_R$. The maximum bandwidth, combined with the maximum absorption power, is achieved when the amorphous structure factor, or grain size, is of the order of the domain wall thickness in a conventional ferromagnet that is of the order of ${(J/D_R)}^{1/2}$ lattice spacings.

We first apply the functional-integral approach to a multiband Hubbard model near the critical pairing temperature and derive a generic effective action that is quartic in the fluctuations of the pairing order parameter. Then we consider time-reversal-symmetric systems with uniform (i.e., at both low momentum and low frequency) pairing fluctuations in a unit cell and derive the corresponding time-dependent Ginzburg-Landau (TDGL) equation. In addition to the conventional intraband contribution that depends on the derivatives of the Bloch bands, we show that the kinetic coefficients of the TDGL equation have a geometric contribution that is controlled by both the quantum-metric tensor of the underlying Bloch states and their band-resolved quantum-metric tensors. Furthermore, we show that thermodynamic properties such as the London penetration depth, Ginzburg-Landau (GL) coherence length, GL parameter, and upper critical magnetic field have an explicit dependence on quantum geometry.

Experimental observation of coherent oscillations in a Rydberg atom chain [H. Bernien et al., Nature (London) 551, 579 (2017)] has led to the discovery of quantum many-body scars (QMBSs) which is a new paradigm for ergodicity breaking. The experimental findings in the Rydberg chain can be well captured by a kinetically constrained model called the “PXP” model, which has been shown to host the eigenstate thermalization hypothesis (ETH)-violating scar states in the middle of the spectrum. Much effort has been put into identifying similar kinetically restricted systems that show a violation of ETH. In this paper, we study the QMBSs that can arise in one such model, namely the spin-1 Kitaev chain, where owing to some conserved quantities, the Hilbert space gets fragmented into unequal disconnected subspaces. Recently, You et al. [Phys. Rev. Res. 4, 013103 (2022)] showed that the ground state sector of this chain can be mapped exactly onto the prototypical PXP model and thus hosts QMBSs. Here, we demonstrate that the phenomenon of scarring is also present in other sectors, and in particular, we identify a sector that exhibits substantially more scarring than the ground state one. We propose an initial state and numerically demonstrate that its fidelity revivals are pronounced and longer lived than those in the PXP model.

We present a theory of optical excitations in binary plasmonic supercrystals that are made out of two types of metal nanoparticles. Compared to monodisperse supercrystals, binary crystals have a larger number of plasmonic bands. Their dispersion is governed by the lattice symmetry, unit cell parameters, and shape and material composition of the nanoparticle building blocks. We develop a quantum description of the plasmon polaritons in supercrystals that starts from the dipole and quadrupole excitations of the nanoparticles, their interaction, and their coupling to photons. We show how to use group theory to analyze the plasmon- and photon-induced supercrystal states and their interaction. Plasmon-polaritons of binary metallic supercrystals are in the regime of ultrastrong and deep strong light-matter interaction; i.e., the coupling strength is on the same order as the photon energy. One consequence of the strong interaction is that quadrupolar plasmon modes and photons with energies well above the plasmon energies have to be taken into account to calculate the polariton dispersion. A cesium chloride crystal of two nanoparticles with different dipole and quadrupole energies serves as the example structure to show how the plasmon-polariton dispersion depends on the properties of the nanoparticles and supercrystal structure. The tools presented here can be used to predict and analyze any type of optically active excitation in supercrystals. The results show how to differentiate the optical properties of binary nanoparticle supercrystals into properties that inflexibly depend on lattice symmetry and properties that can be finely tuned by choosing the nanoparticle composition and shape.

We propose a scheme to implement the self-consistent optimization of the trial wave function within the constrained path auxiliary field quantum Monte Carlo (CP-AFQMC) method in the framework of natural orbitals. In this scheme, a new trial wave function in the form of a Slater determinant is constructed from the CP-AFQMC results by diagonalizing the mixed estimator of the one-body reduced density matrix. We compare two ways (from real and mixed estimators in CP-AFQMC) to calculate the one-body reduced density matrix in the self-consistent process and study the ground state of a doped two-dimensional Hubbard model to test the accuracy of the two schemes. By comparing the local density, occupancy, and ground state energy we find the scheme in which a one-body reduced density matrix is calculated from the mixed estimator is computationally more efficient and provides more accurate results with less fluctuation. The local densities from the mixed estimator scheme agree well with the numerically exact values. This scheme provides a useful tool for studying strongly correlated electron systems.

The realization of Majorana corner modes generally requires unconventional superconducting pairing or $s$-wave pairing. However, the bulk nodes in unconventional superconductors and the low $T_c$ of $s$-wave superconductors are not conducive to the experimental observation of Majorana corner modes. Here, we show the emergence of a Majorana corner mode at each corner of a two-dimensional topological insulator in proximity to a $d+i{d}^{\prime }$ pairing superconductor, such as heavily doped graphene or especially a twisted bilayer of a cuprate superconductor, e.g., ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+\delta }$, which has recently been proposed as a fully gapped chiral $d_{x^2-y^2}+i{d}_{xy}$ superconductor with $T_c$ close to its native 90 K, and an in-plane magnetic field. By numerical calculation and intuitive edge theory, we find that the interplay of the proximity-induced pairing and Zeeman field can introduce opposite Dirac masses on adjacent edges of the topological insulator, which creates one zero-energy Majorana mode at each corner. Our scheme offers a feasible route to achieve and explore Majorana corner modes in a high-temperature platform without bulk superconductor nodes.

We describe the dynamics of a transverse spin-helix state—a product state with spatially rotating magnetization—under XXZ spin chain evolution. Due to experimental relevance we especially focus on magnetization dynamics. At long times the $U\left(1\right)$ symmetry of the Hamiltonian is restored, leading to the decay of transverse magnetization, which can be described as an exponential decay of a spatially harmonic profile. We show that the dependence of the short- and intermediate-time decay timescale, which in principle depends on all different parameters, like the wave vector of the initial helix, the anisotropy, etc., can be described well by a single scaling function. We also briefly discuss the evolution of magnetization current.

We investigate the feasibility of minimum absorption and minimum broadening of pulse propagation in an inhomogeneously broadened semiconductor quantum dot medium. The phonon interaction is inevitable in studying any semiconductor quantum dot system. We have used the polaron transformation technique to deal with quantum dot phonon interaction in solving system dynamics. We demonstrate that a short pulse can propagate inside the medium with minimal absorption and broadening in pulse shape. The stable pulse area becomes slightly higher than the prediction of the pulse area theorem and is also dependent on the environment temperature. The change in the final pulse shape is explained very well by numerically solving the propagation equation supported by the susceptibility of the medium. Our system also exhibits the pulse breakup phenomena for higher input pulse areas. Therefore, the considered scheme can have important applications in quantum communication, quantum information, and mode-locking with the advantage of scalability and controllability.

${\mathrm{Co}}_3{\mathrm{Sn}}_2{\mathrm{S}}_2$ has been established as a prototype of a magnetic Weyl semimetal, exhibiting a giant anomalous Hall effect in its ferromagnetic phase. An attractive feature of this material is that Weyl points lie close to the Fermi level, so one can expect a high reactivity of the topological properties to hole or electron doping. We present here a direct observation with angle-resolved photoemission spectroscopy of the evolution of the electronic structure under different types of substitutions: In for Sn (hole doping outside the kagome Co plane), Fe for Co (hole doping inside the kagome Co plane), and Ni for Co (electron doping inside the kagome Co plane). We observe clear shifts of selected bands, which are due both to doping and to the reduction of the magnetic splitting by doping. We discriminate between the two by studying the temperature evolution from a ferromagnetic to paramagnetic state. We discuss these shifts with the help of density-functional theory calculations using the virtual crystal approximation. We find that these calculations reproduce rather well the evolution with In, but largely fail to capture the effect of Fe and Ni, where local behavior at the impurity site plays an important role.

We calculate the frequency-dependent longitudinal and Hall conductivities and the Faraday and Kerr rotation angles for a single sheet of anisotropic Dirac semimetal protected by nonsymmorphic symmetry in the presence of a Zeeman term coupling to the out-of-plane component of the spin. While the Zeeman term causes a rotation of the plane of polarization of the light, the anisotropy causes the appearance of an elliptically polarized component in an initially linearly polarized beam. The two effects can be combined in a single complex Faraday rotation angle. At the zero-frequency limit, we find a finite value of the Faraday rotation angle, which is given by $2{\alpha }_F$, where ${\alpha }_F$ is the effective fine structure constant associated with the velocity of the linearly dispersing Dirac fermions. We also find a logarithmic enhancement of the Faraday (and Kerr) rotation angles as the frequency of the light approaches the absorption edge associated with the Zeeman-induced gap. While the enhancement is reduced by impurity scattering, it remains significant for an attainable level of material purity. These results indicate that two-dimensional Dirac materials protected by nonsymmorphic symmetry are responsive to Zeeman couplings and can be used as platforms for magneto-optic applications, such as the realization of polarization-rotating devices.

${\mathrm{EuCd}}_2{\mathrm{As}}_2$ has been proposed to be one of the ideal platforms as an intrinsic topological magnetic system, potentially hosting a single pair of Weyl points when it is tuned into the ferromagnetic state with spins aligned out of plane by either external pressure or chemical doping. To investigate the possible realization of an ideal topological state, we have systematically investigated pressure control of the magnetic state, valence, and crystal structure using synchrotron-based time-domain Mössbauer spectroscopy, x-ray absorption spectroscopy, and powder x-ray diffraction. Our experimental results show that the magnetic configuration remains mostly in plane under pressure up to 42.8 GPa and pressure effectively enhances the magnetic ordering temperature. Meanwhile, Eu ions remain divalent when subjected to pressure up to 35.9 GPa, and the trigonal crystal lattice is maintained up to 34.6 GPa. Our work provides valuable experimental data to benchmark future theoretical studies in magnetic topological materials.

Understanding the nature of chemical bonding and lattice dynamics, and their impacts on phonon transport, is crucial for exploring and designing thermoelectric materials with ultralow lattice thermal conductivity. Hexagonal ${\mathrm{TlBiS}}_2$ exhibits a low lattice thermal conductivity ${\kappa }_l$ of 0.67 W/mK at room temperature. The low lattice thermal conductivity is attributed to anharmonic rattling vibration of the weakly bound Tl cations as well as anharmonic motion of the Bi. The soft anharmonic motions of Tl and Bi arise due to the unique electronic structure of this material, which includes substantial cross-gap hybridization involving Tl, Bi, and S. This characteristic leads to a very high dielectric constant, which is favorable for high mobility in the presence of point defects. Different from the long-standing view that acoustic phonons with long mean-free paths invariably are the primary heat carriers contributing to ${\kappa }_l$, we show that 59% of ${\kappa }_l$ of ${\mathrm{TlBiS}}_2$ is contributed by optical phonons. We explicitly analyze the mechanism by which optical phonons in ${\mathrm{TlBiS}}_2$ contribute to heat transport. These optical phonons have large Grüneisen parameters and high anharmonic scattering rate, but in ${\mathrm{TlBiS}}_2$ they also have high group velocities, resulting in significant contributions in this low thermal conductivity material. We find that intrinsic point defects can be utilized to improve the thermoelectric properties of ${\mathrm{TlBiS}}_2$. The Tl vacancy is found to be the dominant defect and can be introduced to improve the band degeneracy and transport properties. Calculations demonstrate that ${\mathrm{V}}_{\mathrm{Tl}}$ is a shallow acceptor. Adjusting the Fermi level using Tl vacancies to increase the carrier concentration of $p$-type ${\mathrm{TlBiS}}_2$ is one important strategy to improve its thermoelectric performance. Our paper provides one method for studying and exploring applications with ultralow lattice thermal conductivity and improving thermoelectric properties using intrinsic point defects.

Colloidal semiconductor nanocrystals (NCs) are believed to strongly absorb resonant light; this property is key to ongoing applications of NCs as phosphor in light-emitting diodes (LEDs) for lighting, in displays, and photodetectors. However, it has been realized that NCs in a low dielectric medium suffer from a weak permeation of the electromagnetic field in the solid due to formation of depolarization fields, strongly reducing light absorption, as quantified by the local-field factor. For low-dimensional semiconductors, such as one-dimensional (1D) rods and two-dimensional (2D) superlattices, this depolarization field depends critically on the electromagnetic field direction versus the long direction of the material. Here we present atomistic calculations of the screening of the electromagnetic field for individual NCs and technologically important architectures, i.e., 1D and 2D superlattices of epitaxially connected NCs. We also investigate the combined effects of epitaxial connections and excitonic interactions in the particular case of dimers of NCs. Even if it can be improved by a matrix of high dielectric constant, the local-field factor of individual NCs is very low but can increase more than an order of magnitude in NC chains or NC superlattices for an in-line or in-plane electromagnetic field. The calculations of the optical absorptance agree with recent experimental results obtained on superlattices of PbSe and CdSe superlattices. The reduced screening of the electric field in the case of strong epitaxial connections between the NCs was recently invoked to explain that the absorptance of a 2D superlattice approaches the absorptance quantum ($\pi \alpha$, where $\alpha$ is the fine structure constant) observed with semiconductor quantum wells [P.T. Prins et al., Nano Lett. 21, 9426 (2021)]. We conclude that atomically coherent superlattices have a strong light absorption and emission, even in the NC monolayer limit, and are primary candidates for polarization-selective photodetectors and LEDs.

Dispersionless quantum states (“flat bands”) are counterintuitive: with the electron velocity vanishing, our conventional notions of quasiparticle transport are no longer valid. While the standard Drude-Sommerfeld theory predicts vanishing conductivity in trivial dispersionless bands, in the dispersionless topological bands the electronic wave functions entangle leading to unconventional (non-Drude) quantum transport. We here research the quantum transport in topological flat bands, and find that the quantum-geometric (entanglement) contribution gives rise to several quantum transport anomalies. We highlight structurally similar expressions for strong anomalies in thermoelectric response and superfluid flow in the flat bands. The thermopower anomaly in topological flat bands is reaching values of the quantum unit of thermopower ($\frac{k_B}{e}ln2\approx 60\mu \mathrm{V}$/k)—the behavior commensurate with the thermopower anomalies in twisted bilayer graphene at the magic angle [Nat. Phys. 18, 290 (2022)].

Realization of persistent discrete energy states in Co-based compounds due to unquenched orbital angular momentum remains an exciting perspective in systems which favor mixed state of ${\mathrm{Co}}^{2+}$ and ${\mathrm{Co}}^{3+}$ ions, without any chemical substitution. Here, we investigate an inverse spinel ${\mathrm{LiCoVO}}_4$, in which the presence of antisite disorder between V and Co results in ${\mathrm{Co}}^{3+}$ ions along with the expected ${\mathrm{Co}}^{2+}$ ions. A thorough investigation of AC susceptibility reveals the presence of a cluster glass state below 3 K. This is further strengthened by nonequilibrium dynamic studies via magnetic relaxation and memory effects which show the growth of the system through several metastable states. The detailed analysis of the observed Schottky anomaly reveals the presence of persistent discrete energy state of ${\mathrm{Co}}^{3+}$ ions which appears due to octahedral distortion and spin-orbit coupling. This anomaly shifts to higher temperature with increasing field and the calculated value of Lande's $g$ factor signifies that the high and low spin states of ${\mathrm{Co}}^{3+}$ are energetically close to each other. We believe that our investigations provides legitimate evidence against the well-established hypothesis of complete quenching of orbital angular moment in $3d$-based oxides owing to discretization of energy states.