arXiv subjects

Haiming Deng

Publications and source records attributed to Haiming Deng.

17 recordsLinked to original sources

arXiv2026

Stable three-dimensional solitons in spin-orbit-coupled atomic-molecular condensates

We elaborate a mechanism for the creation of stable three-dimensional (3D) solitons in spin-orbit-coupled (SOC) atomic-molecular Bose-Einstein condensate, modeled by the mean-field equations with the quadratic three-wave interaction, characterized by mismatch $\alpha $. The planar (effectively two-dimensional) SOC is applied to the soliton's atomic component, structuring it as a mixed mode (MM) or semi-vortex (SV). The molecular component of the SV soliton is shaped as a 3D vortex, while the molecular component in the MM soliton is an MM too. The solitons exist up to a critical value of $\alpha $. The system demonstrates a relatively large norm share of the vortex components, exceeding $50\%$ of the total norm, which is an essential feature of SOC-supported solitons. This is scheme for realizing stable vortex solitons in free space with the quadratic nonlinearity.

quant-ph↗

arXiv2025

Phase transitions and dynamics of one-dimensional solitons in spin-orbit-coupled Bose-Bose mixtures

We investigate the formation, stability, and dynamics of solitons in a one-dimensional binary Bose-Einstein condensate under the action of the spin-orbit-coupling (SOC) and Lee-Huang-Yang (LHY) correction to the underlying system of the Gross-Pitaevskii equations. We identify the semi-dipole (SD) family of solitons and thoroughly analyze its properties. The numerical analysis reveals intricate bifurcations, including transitions from real to complex-valued stationary wavefunctions of the SD solitons and norm-dependent dynamical instabilities. Stability maps in the plane of the solitons' norm and interaction strength exhibit areas of monostability, oscillatory behavior, and soliton splitting. Solitons with complex stationary wavefunctions emerge as ground states in broad parameter areas, due to the effects of the LHY terms. The other soliton species, in the form of mixed modes (MMs), does not feature the compexification bifurcation. In the LHY-dominated regime, the SD and MM solitons exhibit identical values of the energy for the same norm. The results deepen the understanding of nonlinear matter-wave states and reveal multi-stable ones in quantum gases.

cond-mat.quant-gas↗

arXiv2024

Composite solitary vortices of three-wave mixing in quasi-phase-matched photonic crystals

We report the composite vortex solitons of three-wave mixing propagate stably in a three-dimensional (3D) quasi-phase-matched photonic crystals (QPM-PhC). The modulation of QPM-PhC is designed as a checkerboard pattern. The vortex solitons, composed by three waves ($\omega_{1,2,3}$) propagating through the lattices, exhibit a four-spotted discrete type, which gives rise to four distinct modes: zero-vorticity, vortex, anti-vortex, and quadrupole. The composite vortex solitons result from combinations of these modes and lead to four cases: vortex doubling, hidden vortices, vortex up-conversion, and anti-vortex up-conversion. Our findings indicate that all solitons can propagate stably through the crystals for 10 centimeters; however, only the vortex-doubling case remains stable over longer distances. This work enhances the understanding of vortex beam manipulation within 3D QPM-PhCs.

physics.optics↗

arXiv2024

Semi-vortex solitons and their excited states in spin-orbit-coupled binary bosonic condensates

It is known that two-dimensional two-component fundamental solitons of the semi-vortex (SV) type, with vorticities $(s_{+},s_{-})=(0,1)$ in their components, are stable ground states (GSs) in the spin-orbit-coupled (SOC) binary Bose-Einstein condensate with the contact self-attraction acting in both components, in spite of the possibility of the critical collapse in the system. However, excited states(ESs) of the SV solitons, with the vorticity set $(s_{+},s_{-})=( S_{+},S_{+}+1)$ and $S_{+}=1,2,3,...$, are unstable in the same system. We construct ESs of SV solitons in the SOC system with opposite signs of the self-interaction in the two components. The main finding is stability of the ES-SV solitons, with the extra vorticity (at least) up to $S_{+}=6$. The threshold value of the norm for the onset of the critical collapse, $N_{\mathrm{thr}}$, in these excited states is higher than the commonly known critical value, $N_{c}\approx 5.85$,associated with the single-component Townes solitons, $N_{\mathrm{thr}}$ increasing with the growth of $S_{+}$. A velocity interval for stable motion of the GS-SV solitons is found too. The results suggest a solution for the challenging problem of the creation of stable vortex solitons with high topological charges.

cond-mat.quant-gas↗

arXiv2023

Hydrogen induces chiral conduction channels in the topological magnet

Chirality, a characteristic handedness that distinguishes 'left' from 'right', cuts widely across all of nature$^1$, from the structure of DNA$^2$ to opposite chirality of particles and antiparticles$^3$. In condensed matter chiral fermions have been identified in Weyl semimetals$^4$ through their unconventional electrodynamics arising from 'axial' charge imbalance between chiral Weyl nodes of topologically nontrivial electronic bands. Up to now it has been challenging or impossible to create transport channels of Weyl fermions in a single material that could be easily configured for advancing chiral logic or spintronics$^{5,6}$. Here we generate chirality-directed conduction channels in inversion-symmetric Weyl ferromagnet (FM) $MnSb_2Te_4$, emergent from a deep connection between chirality in reciprocal and real space. We alter the bandstructure on-demand with an intake and a subsequent release of ionic hydrogen ($H^+$) $-$ a process we show to induce the tilt and rotation of Weyl bands. The transformed Weyl FM states feature a doubled Curie temperature $\geq50K$ and an enhanced angular transport chirality synchronous with a rare field-antisymmetric longitudinal resistance $-$ a low-field tunable 'chiral switch' that roots in the interplay of Berry curvature$^7$, chiral anomaly$^8$ and hydrogen-engendered mutation of Weyl nodes.

cond-mat.mtrl-sci↗

arXiv2021

Compositional Control and Optimization of Molecular Beam Epitaxial Growth of (Sb2Te3)x(MnSb2Te4)y Magnetic Topological Insulators

Magnetic topological insulators such as MnBi2Te4 and MnSb2Te4 are promising hosts of novel physical phenomena such as quantum anomalous Hall effect and intrinsic axion insulator state, both potentially important for the implementation in topological spintronics and error-free quantum computing. In the bulk, the materials are antiferromagnetic but appropriate stacking with non-magnetic layers or excess Mn in the crystal lattice can induce a net ferromagnetic alignment. In this work we report the growth of (Sb2Te3)x(MnSb2Te4)y layers with varying Mn content by molecular beam epitaxy. The Mn flux fraction provided during growth controls the percent of MnSb2Te4 that is formed in the resulting layers by a self-assembly process. Highly crystalline layers with compositions varying between Sb2Te3 (y=0) and MnSb2Te4 (x=0) were obtained. The results show that Mn incorporates as a structural component to form MnSb2Te4, and as an impurity element both in Sb2Te3 and in MnSb2Te4. Two modifications of the growth conditions were implemented to enhance the incorporation of Mn as a structural element to form MnSb2Te4. Annealing of a thin portion of the layer at the beginning of growth (pre-anneal step), and increasing the growth temperature, both result in a larger percent of MnSb2Te4 for similar Mn flux fractions during growth. Samples having at least a few percent of MnSb2Te4 layers exhibit ferromagnetic behavior likely due to the excess Mn in the system which stabilizes on Sb sites as MnSb antisite defects.

cond-mat.mtrl-sci↗

arXiv2021

Systemic Consequences of Disorder in Magnetically Self-Organized Topological MnBi$_{2}$Te$_{4}/$(Bi$_{2}$Te$_{3}$)$_{n}$ Superlattices

MnBi$_{2}$Te$_{4}/$(Bi$_{2}$Te$_{3}$)$_{n}$ materials system has recently generated strong interest as a natural platform for realization of the quantum anomalous Hall (QAH) state. The system is magnetically much better ordered than substitutionally doped materials, however, the detrimental effects of certain disorders are becoming increasingly acknowledged. Here, from compiling structural, compositional, and magnetic metrics of disorder in ferromagnetic MnBi$_{2}$Te$_{4}/$(Bi$_{2}$Te$_{3}$)$_{n}$ it is found that migration of Mn between MnBi$_{2}$T$e_{4}$ septuple layers (SLs) and otherwise non-magnetic Bi$_{2}$Te$_{3}$ quintuple layers (QLs) has systemic consequences - it induces ferromagnetic coupling of Mn-depleted SLs with Mn-doped QLs, seen in ferromagnetic resonance as an acoustic and optical resonance mode of the two coupled spin subsystems. Even for a large SL separation (n $\gtrsim$ 4 QLs) the structure cannot be considered as a stack of uncoupled two-dimensional layers. Angle-resolved photoemission spectroscopy and density functional theory studies show that Mn disorder within an SL causes delocalization of electron wavefunctions and a change of the surface bandstructure as compared to the ideal MnBi$_{2}$Te$_{4}/$(Bi$_{2}$Te$_{3}$)$_{n}$. These findings highlight the critical importance of inter- and intra-SL disorder towards achieving new QAH platforms as well as exploring novel axion physics in intrinsic topological magnets.

cond-mat.mtrl-sci↗

arXiv2021

Topological surface currents accessed through reversible hydrogenation of the three-dimensional bulk

Hydrogen, the smallest and most abundant element in nature, can be efficiently incorporated within a solid and drastically modify its electronic state - it has been known to induce novel magnetoelectric effects in complex perovskites and modulate insulator-to-metal transition in a correlated Mott oxide. Here we demonstrate that hydrogenation resolves an outstanding challenge in chalcogenide classes of three-dimensional (3D) topological insulators and magnets - the control of intrinsic bulk conduction that denies access to quantum surface transport. With electrons donated by a reversible binding of H+ ions to Te(Se) chalcogens, carrier densities are easily changed by over 10^20 cm^-3, allowing tuning the Fermi level into the bulk bandgap to enter surface/edge current channels. The hydrogen-tuned topological materials are stable at room temperature and tunable disregarding bulk size, opening a breadth of platforms for harnessing emergent topological states.

cond-mat.mtrl-sci↗

arXiv2020

Observation of high-temperature quantum anomalous Hall regime in intrinsic MnBi$_2$Te$_4$/Bi$_2$Te$_3$ superlattice

The quantum anomalous Hall effect is a fundamental transport response of a topologically non-trivial system in zero magnetic field. Its physical origin relies on the intrinsically inverted electronic band structure and ferromagnetism, and its most consequential manifestation is the dissipation-free flow of chiral charge currents at the edges that can potentially transform future quantum electronics. Here we report a previously unknown Berry-curvature-driven anomalous Hall regime ('Q-window') at above-Kelvin temperatures in the magnetic topological bulk crystals where through growth Mn ions self-organize into a period-ordered MnBi$_2$Te$_4$/Bi$_2$Te$_3$ superlattice. Robust ferromagnetism of the MnBi$_2$Te$_4$ monolayers opens a large surface gap, and anomalous Hall conductance reaches an $e^2/h$ quantization plateau when the Fermi level is tuned into this gap within a Q-window in which the anomalous Hall conductance from the bulk is to a high precision zero. The quantization in this new regime is not obstructed by the bulk conduction channels and thus should be present in a broad family of topological magnets.

cond-mat.mtrl-sci↗

arXiv2020

Designer topological insulator with enhanced gap and suppressed bulk conduction in Bi2Se3/Sb2Te3 ultra-short period superlattices

A novel approach to reduce bulk conductance by the use of short period superlattices (SL) of two alternating topological insulator layers is presented. Evidence for a superlattice gap enhancement (SGE) was obtained from the observed reduction of bulk background doping by more than one order of magnitude, from 1.2x1020 cm-3 to 8.5x1018 cm-3 as the period of Bi2Se3/Sb2Te3 SLs is decreased from 12 nm to 5 nm, respectively. Tight binding calculations show that in the very thin period regime, a significant SGE can be achieved by the appropriate choice of materials. The ultrathin SL of alternating Bi2Se3 and Sb2Te3 layers behaves as a new designer material with a bulk bandgap as much as 60% larger than the bandgap of the constituent layer with the largest bandgap, while retaining topological surface features. Analysis of the weak antilocalization (WAL) cusp evident in the low temperature magneto-conductance of a very thin period SL sample grown confirms that the top and bottom surfaces of the SL structure behave as Dirac surface states. This approach represents a promising and yet to be explored platform for building truly insulating bulk TIs.

cond-mat.mtrl-sci↗

arXiv2019

Spin memory of the topological material under strong disorder

Robustness to disorder - the defining property of any topological state - has been mostly tested in low-disorder translationally-invariant materials systems where the protecting underlying symmetry, such as time reversal, is preserved. The ultimate disorder limits to topological protection are still unknown, however, a number of theories predict that even in the amorphous state a quantized conductance might yet reemerge. Here we report a directly detected robust spin response in structurally disordered thin films of the topological material Sb2Te3 free of extrinsic magnetic dopants, which we controllably tune from a strong (amorphous) to a weak crystalline) disorder state. The magnetic signal onsets at a surprisingly high temperature (~ 200 K) and eventually ceases within the crystalline state. We demonstrate that in a strongly disordered state disorder-induced spin correlations dominate the transport of charge - they engender a spin memory phenomenon, generated by the nonequilibrium charge currents controlled by localized spins. The negative magnetoresistance (MR) in the extensive spin-memory phase space is isotropic. Within the crystalline state, it transitions into a positive MR corresponding to the weak antilocalization (WAL) quantum interference effect, with a 2D scaling characteristic of the topological state. Our findings demonstrate that these nonequilibrium currents set a disorder threshold to the topological state; they lay out a path to tunable spin-dependent charge transport and point to new possibilities of spin control by disorder engineering of topological materials

cond-mat.mtrl-sci↗

arXiv2016

Stable topological insulators achieved using high energy electron beams

Topological insulators are transformative quantum solids with immune-to-disorder metallic surface states having Dirac band structure. Ubiquitous charged bulk defects, however, pull the Fermi energy into the bulk bands, denying access to surface charge transport. Here we demonstrate that irradiation with swift ($\sim 2.5$ MeV energy) electron beams allows to compensate these defects, bring the Fermi level back into the bulk gap, and reach the charge neutrality point (CNP). Controlling the beam fluence we tune bulk conductivity from \textit{p}- (hole-like) to \textit{n}-type (electron-like), crossing the Dirac point and back, while preserving the Dirac energy dispersion. The CNP conductance has a two-dimensional (2D) character on the order of ten conductance quanta $G_0 =e^2/h$, and reveals, both in Bi$_2$Te$_3$ and Bi$_2$Se$_3$, the presence of only two quantum channels corresponding to two topological surfaces. The intrinsic quantum transport of the topological states is accessible disregarding the bulk size.

cond-mat.mtrl-sci↗

arXiv2015

Cluster Gutzwiller study of Bose-Hubbard ladder: ground-state phase diagram and many-body Landau-Zener dynamics

We present a cluster Gutzwiller mean-field study for ground states and time-evolution dynamics in the Bose-Hubbard ladder (BHL), which can be realized by loading Bose atoms in double-well optical lattices. In our cluster mean-field approach, we treat each double-well unit of two lattice sites as a coherent whole for composing the cluster Gutzwiller ansatz, which may remain some residual correlations in each two-site unit. For a unbiased BHL, in addition to conventional superfluid phase and integer Mott insulator phases, we find that there are exotic fractional insulator phases if the inter-chain tunneling is much stronger than the intra-chain one. The fractional insulator phases can not be found by using a conventional mean-field treatment based upon the single-site Gutzwiller ansatz. For a biased BHL, we find there appear single-atom tunneling and interaction blockade if the system is dominated by the interplay between the on-site interaction and the inter-chain bias. In the many-body Landau-Zener process, in which the inter-chain bias is linearly swept from negative to positive or vice versa, our numerical results are qualitatively consistent with the experimental observation [Nat. Phys. \textbf{7}, 61 (2011)]. Our cluster bosonic Gutzwiller treatment is of promising perspectives in exploring exotic quantum phases and time-evolution dynamics of bosonic particles in superlattices.

cond-mat.quant-gas↗

arXiv2014

Emergent surface superconductivity of nanosized Dirac puddles in a topological insulator

Surfaces of three-dimensional topological insulators have emerged as one of the most remarkable states of condensed quantum matter1-5 where exotic electronic phases of Dirac particles should arise1,6-8. Here we report a discovery of surface superconductivity in a topological material (Sb2Te3) with resistive transition at a temperature of ~9 K induced through a minor tuning of growth chemistry that depletes bulk conduction channels. The depletion shifts Fermi energy towards the Dirac point as witnessed by about two orders of magnitude reduction of carrier density and by very large (~25,000 cm^2/Vs) carrier mobility. Direct evidence from scanning tunneling spectroscopy and from magnetic response show that the superconducting condensate forms in surface puddles at unprecedentedly higher temperatures, near 60 K and above. The new superconducting state we observe to emerge in puddles can be tuned by the topological material's parameters such as Fermi velocity and mean free path through band engineering; it could potentially become a hunting ground for Majorana modes6 and lead to a disruptive paradigm change9 in how quantum information is processed.

cond-mat.supr-con↗

arXiv2014

Singular robust room-temperature spin response from topological Dirac fermions

Topological insulators are a class of solids in which the nontrivial inverted bulk band structure gives rise to metallic surface states that are robust against impurity scattering. In three-dimensional (3D) topological insulators, however, the surface Dirac fermions intermix with the conducting bulk, thereby complicating access to the low energy (Dirac point) charge transport or magnetic response. Here we use differential magnetometry to probe spin rotation in the 3D topological material family (Bi$_2$Se$_3$, Bi$_2$Te$_3$, and Sb$_2$Te$_3$). We report a paramagnetic singularity in the magnetic susceptibility at low magnetic fields which persists up to room temperature, and which we demonstrate to arise from the surfaces of the samples. The singularity is universal to the entire family, largely independent of the bulk carrier density, and consistent with the existence of electronic states near the spin-degenerate Dirac point of the 2D helical metal. The exceptional thermal stability of the signal points to an intrinsic surface cooling process, likely of thermoelectric origin, and establishes a sustainable platform for the singular field-tunable Dirac spin response.

cond-mat.mtrl-sci↗

arXiv2014

Photon-induced sideband transitions in a many-body Landau-Zener process

We investigate the many-body Landau-Zener (LZ) process in a two-site Bose-Hubbard model driven by a time-periodic field. We find that the driving field may induce sideband transitions in addition to the main LZ transitions. These photon-induced sideband transitions are a signature of the photon-assisted tunneling in our many-body LZ process. In the strong interaction regime, we develop an analytical theory for understanding the sideband transitions, which is confirmed by our numerical simulation. Furthermore, we discuss the quantization of the driving field. In the effective model of the quantized driving field, the sideband transitions can be understood as the LZ transitions between states of different "photon" numbers.

cond-mat.quant-gas↗

arXiv2011

Nonlinear quantum interferometry with Bose condensed atoms

In quantum interferometry, it is vital to control and utilize nonlinear interactions for achieving high-precision measurements. Attribute to their long coherent time and high controllability, ultracold atoms including Bose condensed atoms have been widely used for implementing quantum interferometry. Here, we review the recent progresses in theoretical studies of quantum interferometry with Bose condensed atoms. In particular, we focus on the nonlinear phenomena induced by the atom-atom interaction and how to control and utilize these nonlinear phenomena. Under the mean-field description, due to the atom-atom interaction, matter-wave solitons appear in the interference patterns, and macroscopic quantum self-trapping exists in the Bose-Josephson junctions. Under the many-body description, the atom-atom interaction can generate non-classical entanglement, which may be utilized to achieve high-precision measurements beyond the standard quantum limit.

cond-mat.quant-gas↗