Spin transport of indirect excitons
J. R. Leonard, Y. Kuznetsova, Sen Yang, L. V. Butov, T. Ostatnický, A. Kavokin, A. C. Gossard
通过测量激子辐射的空间分辨圆偏振态，观察了GaAs/AlGaAs耦合量子阱中间接激子的自旋输运。激子自旋输运超过几个微米起源于长的自旋弛豫时间和间接激子的长寿命。
Spin transport of indirect excitons in GaAs/AlGaAs coupled quantum wells was observed by measuring the spatially resolved circular polarization of exciton emission. Exciton spin transport over several microns originates from a long spin relaxation time and long lifetime of indirect excitons.
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Nonlinear Optical Probe of Indirect Excitons
提出了利用非线性光学研究耦合量子阱中空间间接激子的方法。我们证明，尽管他们消失的振子强度，间接激子可以强烈地有助于光致反射率和克尔旋转。这种现象是由直接激子和间接激子之间的相互作用控制的。间接激子的暗态和亮态都可以用这些非线性光学技术探测。
The exciton system in double quantum well is considered under condition when the ground state is the spatially indirect exciton. At high pumping growth of the exciton concentration can lead to so significant increase of the indirect exciton energy that becomes equal to the direct exciton energy. Then further increase of pumping leads to formation of mixed direct - indirect exciton phase. A rough estimate of the exciton energy in the mixed phase explains puzzling features of some recent exciton measurements. An experiment that would reveal main characteristic features of the mixed phase is sugg…
Spin transport of indirect excitons in GaAs coupled quantum wells
通过测量激子辐射的空间分辨圆偏振态，观察了GaAs/AlGaAs耦合量子阱中间接激子的自旋输运。激子的自旋输运源于间接激子的长自旋弛豫时间和长寿命。
Coherent control of indirect excitonic qubits in optically driven quantum dot molecules
我们提出了一个在量子点分子中定义和操纵间接中性激子量子比特的光电方案。我们证明了相干动力学的间接激子弹性退相干效应，包括直接激子自发复合。对于具有大的点间间隔的分子，激子修饰光谱产生经常被忽视的空间间接激子状态之间的避免交叉。利用Feshbach投影方法提取了多能级激子组态的有效二能级系统哈密顿量。利用时间相关的电场扫描设计了量子比特态的绝热操纵。激子动力学产生的必要条件，量子比特初始化和近酉旋转的皮秒时间尺度，由系统内部动力学驱动。尽管激光激发、电荷隧穿和点间偶极-偶极相互作用的强烈影响，间接激子的有效弛豫时间比直接激子自发复合时间长得多，使得间接激子在更复杂的方案中成为潜在的基本量子比特。
Transport of Indirect Excitons in a Potential Energy Gradient
我们实现了一个潜在的能量梯度-斜坡-间接激子在恒定电压下使用一个形状的电极。我们研究了间接激子沿斜坡的输运，并观察到激子输运距离随密度和温度的增加而增加。
We present spatially- and spectrally-resolved photoluminescence measurements of indirect excitons in high magnetic fields. Long indirect exciton lifetimes give the opportunity to measure magnetoexciton transport by optical imaging. Indirect excitons formed from electrons and holes at zeroth Landau levels (0e - 0h indirect magnetoexcitons) travel over large distances and form a ring emission pattern around the excitation spot. In contrast, the spatial profiles of 1e - 1h and 2e - 2h indirect magnetoexciton emission closely follow the laser excitation profile. The 0e - 0h indirect magnetoexciton…
We report on spatially- and time-resolved emission measurements and observation of transport of indirect excitons in ZnO/MgZnO wide single quantum wells.
Spatially indirect excitons with displaced wavefunctions of electrons and holes play a pivotal role in a large portfolio of fascinating physical phenomena and emerging optoelectronic applications, such as valleytronics, exciton spin Hall effect, excitonic integrated circuit and high-temperature superfluidity. Here, we uncover three types of spatially indirect excitons (including their phonon replicas) and their quantum-confined Stark effects in hexagonal boron nitride encapsulated bilayer WSe2, by performing electric field-tunable photoluminescence measurements. Because of different out-of-pla…
Kinetics of indirect excitons in the optically-induced exciton trap
本文报道了光诱导激子陷阱中间接激子低温气体的动力学。激子在激光激发的区域被发现迅速-在4 ns内-冷却到晶格温度T = 1.4 K，而在陷阱中心的激子被发现是冷的-基本上在晶格温度-即使在激发脉冲。激子到陷阱中心的加载时间约为40 ns，比冷却时间长，但比间接激子的寿命短。所观察到的时间层次是有利于创建一个密集和冷激子气体中的光诱导陷阱和原位控制的气体通过改变激子重组前的空间和时间的激发分布。
We report on the principle and realization of an excitonic device: a ramp that directs the transport of indirect excitons down a potential energy gradient created by a perforated electrode at constant voltage. The device provides an experimental proof of principle for controlling exciton transport with electrode density gradients. We observed that the exciton transport distance along the ramp increases with increasing exciton density. This effect is explained in terms of disorder screening by repulsive exciton-exciton interactions.
We demonstrate experimental proof of principle for a stirring potential for indirect excitons. The azimuthal wavelength of this stirring potential is set by the electrode periodicity, the amplitude is controlled by the applied AC voltage, and the angular velocity is controlled by the AC frequency.
Non-linear dynamics and inner-ring photoluminescence pattern of indirect excitons
研究了双量子阱异质结中光学产生的超冷间接激子的光致发光动力学。超过阈值激光激发，我们的实验揭示了所谓的内部光致发光环的幽灵。它的特征在于环形光致发光，一旦激光激发终止，该环形光致发光突然崩溃。我们表明，光谱分辨动力学是一致的激子起源的内环，这是由于局部加热的间接激子的激光激发。为了证实这一解释，并排除间接激子的电离，我们评估的激子密度，从光致发光发射的能量提取。结果表明，光注入载流子在这种情况下起着至关重要的作用，因为这些被困在我们的场效应器件，然后改变控制间接激子的约束的静电势。这种破坏性的影响模糊了激子浓度的估计。然而，通过将双量子阱置于超晶格之后来平滑双量子阱的静电环境，它被抑制。在这种改进的几何形状，然后我们估计，激子密度保持一个数量级小于临界密度的间接激子的电离（或莫特过渡）在该制度的内环形成。
We propose a coherent control scheme based on the optical Stark effect in optically generated excitons in quantum dot molecules (QDMs). We show that, by the combined action of voltage bias detuning sweeps and Rosen-Zener pulsed interactions, it is possible to dynamically generate and modify an anticrossing gap that emerges between the dressed energy levels of long-lived, spatially indirect excitons. We perform numerical and analytic non-perturbative calculations based on the Bloch-Feshbach formalism, which demonstrate that this effect induces a mechanism of coherent population trapping of indi…
We present a concept and experimental proof of principle for split-gate devices for indirect excitons (IXs). The split-gate forms a narrow channel, a point contact, for IX current. Control of IX flow through the split-gate with both gate voltage and excitation power is demonstrated.
Localization-Delocalization Transition of Indirect Excitons in Lateral Electrostatic Lattices
研究了GaAs/AlGaAs耦合线性量子阱中间接激子的输运。随着晶格振幅的减小或激子密度的增加，可以观察到跨晶格输运的定域-离域跃迁（LDT）。激子相互作用能在跃迁处接近晶格振幅。这些结果与模型一致，该模型将LDT归因于激子气体通过外部势的相互作用诱导的渗流。我们还讨论了应用晶格势估计无序和激子相互作用的强度。
Indirect excitons (IXs) are bound pairs of electrons and holes confined in spatially separated layers. We present wide single quantum well (WSQW) heterostructures with high IX mobility, spectrally narrow IX emission, voltage-controllable IX energy, and long and voltage-controllable IX lifetime. This set of properties shows that WSQW heterostructures provide an advanced platform both for studying basic properties of IXs in low-disorder environments and for the development of high mobility excitonic devices.
Indirect excitons (IXs) in van der Waals transition-metal dichalcogenide (TMD) heterostructures are characterized by a high binding energy making them stable at room temperature and giving the opportunity for exploring fundamental phenomena in excitonic systems and developing excitonic devices operational at high temperatures. We present the observation of IXs at room temperature in van der Waals TMD heterostructures based on monolayers of MoS$_2$ separated by atomically thin hexagonal boron nitride. The IXs realized in the TMD heterostructure have lifetimes orders of magnitude longer than lif…
We investigated excitonic absorptions in GaAs/AlAs/GaAs single barrier heterostructure using both photocapacitance and photocurrent spectroscopies at room temperature. Photocapacitance spectra show well defined resonance peak of indirect excitons formed around the Gamma-AlAs barrier. Unlike DC-photocurrent spectra, frequency dependent photocapacitance spectra interestingly red shift, sharpen up and then decrease with increasing tunneling at higher biases. Such dissimilarities clearly point out that different exciton dynamics govern these two spectral measurements. We also argue why such quantu…
Direct and indirect exciton mixing in a slightly asymmetric double quantum well
从理论上研究了微非对称双量子阱在电场和磁场作用下的光吸收谱。最近对10.18/3.82/9.61 nm GaAs Al（_{.33}）Ga（_{.67}）As双量子阱的实验结果清楚地表明，间接激子（IX）和左直接激子（DX）的发光峰随外加电场的变化具有不同的行为。我们表明，在（DX）峰附近的峰的存在下，归因于杂质束缚左（DX）的实验结果，可能是激子状态之间的非平凡的混合的后果。
The objective of this work is to numerically integrate in space and time the effective-mass Schrodinger equation for an excitonic wave packet in a coupled quantum-well system under a time-dependent electric field. Taking as a starting point a time-dependent Hartree potential, we derive the nonlinear dynamical evolution of the excitonic wave function. We found that the system resonant condition can be modified owing to the reaction field generated by a charge dynamically trapped in the quantum-well pair. As a result, this study raises a broader question: is it possible to create an electrostati…
Pattern formation of indirect excitons in coupled quantum wells
利用包含短程两体吸引和三体排斥的非线性薛定谔方程，研究了半导体耦合量子阱中间接激子的空间分布。得到的结果可以解释Lai \emph{et al.} [Lai $et al.$，Science \textbf{303}，503（2004）]观察到的当杂质势阱中受限激子的数量增加时环形激子云先收缩然后膨胀的实验现象。特别地，该模型与Butov \emph{et al.} [Butov $et al.$，Nature \textbf{418}，751（2002）]报道的激子环的模式一致。在更高的密度下，该模型预测了更丰富的模式，可以通过未来的实验进行测试。
Collection of indirect excitons in a diamond-shaped electrostatic trap
我们报告的原则和实现的一种新的陷阱激子-金刚石静电陷阱-它使用一个单一的电极，以创建一个限制的潜力激子。我们还创造了高架钻石陷阱，允许激子气体蒸发冷却。我们观察到收集的激子对陷阱中心的激子密度增加。这种效应是由于激子屏蔽陷阱中的无序。因此，金刚石陷阱表现为光滑的抛物线势，在陷阱中心实现了冷而致密的激子气体。
Two-Dimensional Electrostatic Lattices for Indirect Excitons
我们报告的方法实现二维静电晶格的激子使用图案化的叉指电极。晶格结构由电极图案设定，并且晶格电势的深度由施加的电压控制。我们展示了正方形，六边形，蜂窝晶格由这种方法创建。
Observation of macroscopic coherence in self-organized dipolar excitons
我们报告的实验表明，空间间接激子限制在一个广泛的单量子阱可以表现出宏观空间相干性。扩展相干性自发地建立在间接激子形成独特的环形图案碎裂成微观珠的制度中。这些包含一个大浓度的间接激子在亚开尔文温度，激子的空间相干性是最大的片段附近。
We calculate the binding energy, transition energies, oscillator strength, and absorption coefficient of indirect excitons in transition metal dichalcogenide (TMDC) double layers separated by an integer number of hexagonal boron nitride (h-BN) monolayers. The absorption factor, a dimensionless quantity which gives the fraction of incoming photons absorbed by the indirect excitons in the double layer, is evaluated. The aforementioned optical quantities are obtained for transitions from the ground state to the first two excited states. All quantities are studied as a function of the interlayer s…
We propose a scheme for the controllable preparation of a cold indirect exciton condensate using dipolaritonic setup with an optical pumping. Dipolaritons are bosonic quasiparticles which arise from the coupling between cavity photon (C), direct exciton (DX), and indirect exciton (IX) modes, and appear in a double quantum well embedded in a semiconductor microcavity. Controlling the detuning between modes of the system, the limiting cases of exciton-polaritons and indirect excitons can be realized. Our protocol relies on the initial preparation of an exciton polariton condensate for the far bl…
Coherent driving of direct and indirect excitons in a quantum dot molecule
本文在量子点分子中实现直接、间接及杂化激子的功率依赖Rabi振荡，并通过栅压调控波函数重叠以优化光子图态生成。
Ensembles of indirect or interlayer excitons (IXs) are intriguing systems to explore classical and quantum phases of interacting bosonic ensembles. IXs are composite bosons that feature enlarged lifetimes due to the reduced overlap of the electron-hole wave functions. We demonstrate electric Field control of indirect excitons in MoS2/WS2 hetero-bilayers embedded in a field effect structure with few-layer hexagonal boron nitrite as insulator and few-layer graphene as gate-electrodes. The different strength of the excitonic dipoles and a distinct temperature dependence identify the indirect exci…
Spin-flip Raman scattering of the $Γ$-X mixed exciton in indirect band-gap (In,Al)As/AlAs quantum dots
带隙能量超过1.63 eV的I型（In，Al）As/AlAs量子点的能带结构在动量空间是间接的，导致长寿命激子态，在量子信息中具有潜在的应用。通过混合$Γ$ -和X-导带谷提供对这些激子的光学访问，由此可以获得对它们的自旋状态的控制。这种访问在这里用于研究激子自旋能级结构的共振自旋翻转拉曼散射，使我们能够准确地测量各向异性的空穴和各向同性的电子$g$因素。间接激子及其组分的自旋翻转机制，以及潜在的光学选择规则的确定。自旋翻转强度是$Γ$ -X谷混合强度的可靠量度，实验和理论都证明了这一点。
We combine electron energy-loss spectroscopy and first-principles calculations based on density-functional theory (DFT) to identify the lowest indirect exciton state in the in-plane charge response of hexagonal boron nitride (h-BN) single crystals. This remarkably sharp mode forms a narrow pocket with a dispersion bandwidth of $\sim 100~\text{meV}$ and, as we argue based on a comparison to our DFT calculations, is predominantly polarized along the $Γ\text{K}$-direction of the hexagonal Brillouin zone. Our data support the recent report by Cassabois \emph{et al.} (Nat. Photon. \textbf{10}, 262)…
Skyrmion Formation and Optical Spin-Hall Effect in an Expanding Coherent Cloud of Indirect Excitons
我们提供了一个理论描述的偏振模式和相位奇异性的实验证明最近在凝聚的间接激子[H。High等人，Nature 483，584-588（2012）]。我们表明，平均的电子和空穴轨道运动导致一个可比的自旋轨道相互作用的两种类型的载流子。我们证明了明亮的间接激子的径向相干通量和Dresselhaus自旋轨道相互作用之间的相互作用导致形成自旋域和类似于Skyrmions的拓扑缺陷。我们定性地再现了实验数据的所有特征，并获得了与光学自旋霍尔效应相同的偏振模式，尽管自旋-轨道相互作用的对称性不同。
Indirect excitons (IX) in semiconductor heterostructures are bosons, which can cool below the temperature of quantum degeneracy and can be effectively controlled by voltage and light. IX quantum Bose gases and IX devices were explored in GaAs heterostructures where an IX range of existence is limited to low temperatures due to low IX binding energies. IXs in van der Waals transition-metal dichalcogenide (TMD) heterostructures are characterized by large binding energies giving the opportunity for exploring excitonic quantum gases and for creating excitonic devices at high temperatures. TMD hete…
Transport of indirect excitons and exciton mediated spin transport in a van der Waals heterostructure in magnetic fields
研究在磁场中MoSe₂/WSe₂异质结中间接激子与自旋输运的长程传输特性及其衰减距离与密度的关系。
Influence of the heterointerface sharpness on exciton recombination dynamics in an ensemble of (In,Al)As/AlAs quantum dots with indirect band-gap
研究了间接带隙（In，Al）As/AlAs量子点系综中激子复合的动力学行为。受限制激子的寿命主要受（In，Al）As量子点与AlAs势垒基体之间异质界面的尖锐度的影响。时间分辨光致发光实验和理论模型计算揭示了激子寿命对界面扩散层厚度的强烈依赖性。具有特定光学跃迁能量的激子的寿命变化，因为该能量是针对尺寸、形状和组成不同的量子点获得的。不同的激子寿命，这导致在光致发光与非指数衰减服从幂律函数，可以描述的现象学分布函数，它允许一个解释的光致发光衰减与一个拟合参数。
We perform a $\mathbf{k \cdot p}$ theory analysis of the spectra of the lowest energy and excited states of the excitons in few-layer atomically thin films of InSe taking into account in-plane electric polarizability of the film and the influence of the encapsulation environment. For the thinner films, the lowest-energy state of the exciton is weakly indirect in momentum space, with its dispersion showing minima at a layer-number-dependent wave number, due to an inverted edge of a relatively flat topmost valence band branch of the InSe film spectrum and we compute the activation energy from th…
We have investigated indirect excitons in bulk $2H$-MoS$_2$ using transmission electron energy-loss spectroscopy. The electron energy-loss spectra were measured for various momentum transfer values parallel to the $Γ$K and $Γ$M directions of the Brillouin zone. The results allowed the identification of the indirect excitons between the valence band K$_{\mathrm{v}}$ and conduction band $Λ_{\mathrm{c}}$ points, the $Γ_{\mathrm{v}}$ and K$_{\mathrm{c}}$ points as well as adjacent K$_{\mathrm{v}}$ and K$^{\prime}_\textrm{c}$ points. The energy-momentum dispersions for the K$_{\mathrm{v}}$-$Λ_{\mat…
Electrons and holes residing on the opposing sides of an insulating barrier and experiencing an attractive Coulomb interaction can spontaneously form a coherent state known as an indirect exciton condensate. We study a trilayer system where the barrier is an antiferromagnetic insulator. The electrons and holes here additionally interact via interfacial coupling to the antiferromagnetic magnons. We show that by employing magnetically uncompensated interfaces, we can design the magnon-mediated interaction to be attractive or repulsive by varying the thickness of the antiferromagnetic insulator b…
Cascade spin dynamics of excitons localized in indirect-band-gap (In,Al)As/AlAs quantum dots with type-I band alignment
本研究利用偏振选择光致发光光谱结合磁场，探究I型(In,Al)As/AlAs量子点中间接带隙激子的级联自旋动力学，推导模型并量化各向异性交换劈裂，揭示零磁场光取向的成因。
The exciton recombination and spin dynamics in (In,Al)As/AlAs quantum dots (QDs) with indirect band gap and type-I band alignment are studied. The negligible (less than $0.2~μ$eV) value of the anisotropic exchange interaction in these QDs prevents a mixing of the excitonic basis states with pure spin and allows for the formation of spin polarized bright excitons for quasi-resonant circularly polarized excitation. In a longitudinal magnetic field, the recombination and spin dynamics of the excitons are controlled by the hyperfine interaction between the electron and nuclear spins. A QD blockade…
We present a theory of bilayer two-dimensional electron systems that host a spatially indirect exciton condensate when in thermal equilibrium. Equilibrium bilayer exciton condensates (BXCs) are expected to form when two nearby semiconductor layers are electrically isolated, and when the conduction band of one layer is brought close to degeneracy with the valence band of a nearby layer by varying bias or gate voltages. BXCs are characterized by spontaneous inter-layer phase coherence and counterflow superfluidity. The bilayer system we consider is composed of two transition metal dichalcogenide…
Observations of indirect exciton trapping in one- and two-dimensional magnetic lattices
提出了一种在耦合量子阱中产生和控制磁势的简单方法，用于间接激子磁约束。局部非均匀磁势与周期性分布的局部最小值和最大值，称为磁晶格，被投射到耦合量子阱的平面，并用于空间分布的二维间接激子捕获，在这种情况下，局部间接激子观察。间接激子捕获机制，检查通过控制外部磁场偏置导致的局域激子晶格的移位。
Efficient transport kinetics of indirect excitons in van der Waals heterostructure
本文通过实验发现范德华异质结构中间接激子具有反常的高迁移率，表明在面内无序存在下仍可实现高效输运，与间接激子超流性预测一致。
Theory of polarized photoluminescence of indirect band gap excitons in type-I quantum dots
该研究针对弱交换作用、长寿命的间接激子量子点，理论分析超精细作用、奥弗豪泽场涨落等对激子精细结构的影响，发现其共振光致发光偏振随外磁场的变化规律异于传统量子点。
From spatially indirect to momentum-space indirect exciton by in-plane magnetic field
在GaAs/AlGaAs耦合量子阱中，面内磁场可以显著改变阱间激子的光致发光谱和动力学。这种效应是由于面内磁场引起的阱间激子色散在动量空间中的位移，导致从动量空间直接激子基态到动量空间间接激子基态的跃迁。因此，面内磁场是激子色散工程的有效工具。
Superfluidity of "dirty" indirect excitons in coupled quantum wells
关于超流体在随机场中会发生什么的理论，被称为"脏玻色子“问题，直接关系到目前几个研究小组正在研究的一个真实的实验系统，即耦合半导体量子阱中的激子。我们考虑的情况下，玻色子在二维的随机场，当随机场可以是大的排斥激子激子相互作用能相比，但很小的激子结合能相比。在梯形近似中考虑了激子之间的相互作用。相干势近似使我们能够推导出激子格林函数的随机场强度的范围很广，并在弱散射限制CPA的结果在二阶玻恩近似。对于准二维激子系统，得到了超流组分的密度和超流相变的Kosterlitz无相变温度，发现它们随随机场的增大而减小.
Long exciton spin memory in coupled quantum wells
利用偏振和时间分辨光致发光方法研究了耦合量子阱结构中的空间间接激子。当激发能被调谐到与直接激子态共振时，实现了发射中的强圆偏振度（> 50%）。间接跃迁在泵浦激光脉冲后的几十纳秒内保持偏振，直接表明激子自旋有很长的弛豫时间。所观察到的自旋记忆效应超过了间接激子的辐射寿命。
We study the eigenenergies and optical properties of both direct excitons in a phosphorene monolayer in different dielectric environments, and indirect excitons in heterostructures of phosphorene with hexagonal boron nitride. For these systems, we solve the 2D Schrödinger equation using the Rytova-Keldysh (RK) potential for direct, and both the RK and Coulomb potentials for indirect excitons. The results show that excitons formed from charge carriers with anisotropic effective mass exhibit enhanced (suppressed) optical absorption, compared to their 2D isotropic counterparts, under linearly pol…
Long lifetimes of spatially indirect excitons (IXs), also known as interlayer excitons, make possible long-range IX propagation. Van der Waals heterostructures composed of atomically thin layers of transition-metal dichalcogenides (TMDs) give an opportunity to realize excitons with high binding energies and provide a materials platform for the realization of both excitonic quantum phenomena and excitonic devices. Propagation of IXs in TMD heterostructures is intensively studied. However, in spite of long IX lifetimes, orders of magnitude longer than lifetimes of spatially direct excitons (DXs)…
Quantum Signature Blurred by Disorder in Indirect Exciton Gases
在很低的浴温（约350 mK）下探测耦合量子阱中捕获的间接激子的微观气体的光致发光动力学。我们的实验揭示了间接激子的非线性能量弛豫特性。特别地，我们观察到激子动力学与排斥激子-激子相互作用对结构无序的屏蔽密切相关。对于我们的实验，其中二维激子状态是逐渐定义的，激子散射率的显着增强向最低能量状态与密度增加并没有明确揭示量子统计效应，如玻色刺激。
Localization and interaction of indirect excitons in GaAs coupled quantum wells
我们介绍了一种提高陷阱技术，并利用它来降低间接激子的有效温度。我们观察到狭窄的光致发光线，对应于在无序势的间接激子的个别状态的发射。我们研究了激子-激子相互作用对局域态和离域态激子的影响，发现均匀谱线展宽随密度的增加而增加，在高密度时，均匀谱线展宽占主导地位。
We present a microscopic theory of a photon drag effect that appears in a Bose-Einstein condensate of neutral particles, considering indirect excitons in a double quantum well nanostructure under the action of a circularly polarized electromagnetic field. It is shown that the dynamical polarization of excitons results in a resonant behavior of the exciton photon drag flux when the frequency of light is close to the gap between two energy levels of internal exciton motion. Specifically, we consider the ground and first excited energy states characterized by the angular momentum difference $\pm …
Monolayers of transition metal dichalcogenides (TMDCs) feature exceptional optical properties that are dominated by excitons, tightly bound electron-hole pairs. Forming van der Waals heterostructures by deterministically stacking individual monolayers allows to tune various properties via choice of materials and relative orientation of the layers. In these structures, a new type of exciton emerges, where electron and hole are spatially separated. These interlayer excitons allow exploration of many-body quantum phenomena and are ideally suited for valleytronic applications. Mostly, a basic mode…
We study a capacitor made of three monolayers of transition metal dichalcogenide (TMD) separated by hexagonal Boron Nitride (hBN). We assume that the structure is symmetric with respect to the central layer plane. The symmetry includes the contacts: if the central layer is contacted by the negative electrode, both external layers are contacted by the positive one. As a result a strong enough voltage $V$ induces electron-hole dipoles (indirect excitons) pointing towards one of the external layers. Antiparallel dipoles attract each other at large distances. Thus, the dipoles alternate in the cen…
A supersolid, a counter-intuitive quantum state in which a rigid lattice of particles flows without resistance, has to date not been unambiguously realised. Here we reveal a supersolid ground state of excitons in a double-layer semiconductor heterostructure over a wide range of layer separations outside the focus of recent experiments. This supersolid conforms to the original Chester supersolid with one exciton per supersolid site, as distinct from the alternative version reported in cold-atom systems of a periodic modulation of the superfluid density. We provide the phase diagram augmented by…
An indirect exciton is a bound state of an electron and a hole in spatially separated layers. Two-dimensional indirect excitons can be created optically in heterostructures containing double quantum wells or atomically thin semiconductors. We study theoretically transmission of such bosonic quasiparticles through nano-constrictions. We show that quantum transport phenomena, e.g., conductance quantization, single-slit diffraction, two-slit interference, and the Talbot effect, are experimentally realizable in systems of indirect excitons. We discuss similarities and differences between these phe…
The variety of excitonic states in tungsten-based dichalcogenide monolayers stems from unique interplay between the spin and valley degrees of freedom. One of the exciton species is the indirect exciton (momentum or valley dark), which is responsible to a series of resonances when the monolayer is charge neutral. We investigate the short-range electron-hole exchange interaction of the indirect exciton, as well as its recombination mechanism mediated by impurities. The analysis provides thorough understanding of the energy and polarization of the zero-phonon indirect exciton resonance in the em…
Strain-Driven "Sinusoidal" Valley Control of Hybridized $Γ-\mathrm{K}$ Excitons
该研究通过统一框架揭示了应变驱动下混合Γ-K激子的动态机制，提出了一种连续可调的谷调节器，为谷电子学技术的发展提供了新思路。
Indirect excitons (IXs), also known as interlayer excitons, can form the medium for excitonic devices whose operation is based on controlled propagation of excitons. A proof of principle for excitonic devices was demonstrated in GaAs heterostructures where the operation of excitonic devices is limited to low temperatures. IXs in van der Waals transition-metal dichalcogenide (TMD) heterostructures are characterized by high binding energies making IXs robust at room temperature and offering an opportunity to create excitonic devices operating at high temperatures suitable for applications. Howev…
Superfluidity of indirect momentum space dark dipolar excitons in a double layer with massive anisotropic tilted semi-Dirac bands
本文理论研究圆偏振光与垂直电场调控下1T′-MoS₂双层中暗偶极激子的各向异性超流，并给出解析谱、临界温度及实验验证方案。
Forster energy transfer signatures in optically driven quantum dot molecules
研究了光驱动和电选通隧道耦合量子点分子中的Forster共振能量转移机制。在缀饰激子光谱中发现了两个新的FRET诱导的光学特征。这是由激子能级占据作为泵激光能量和施加的偏压的函数构造的，类似于水平反交叉光谱测量。我们观察到的激子谱线的光谱重量和分裂的重新分配。单个激子之间的FRET诱导分裂的空间直接激子线，远离由于在分子中的电荷隧穿的反交叉。然而，附近的反交叉，一个新的签名出现作为一个弱的卫星线以下的间接激子线。FRET签名也可能发生在间接激子之间，表现为分裂的间接线。在这种情况下，签名也出现在直接双激子状态，因为间接卫星混合在隧道反交叉区域附近。
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