Optical initialization of a single spin-valley in charged WSe2 quantum dots

Abstract

Control and manipulation of single charges and their internal degrees of freedom, such as spins, is a fundamental goal of nanoscience with promising technological applications. Recently, atomically thin semiconductors such as WSe 2 have emerged as a platform for valleytronics, offering rich possibilities for optical, magnetic and electrical control of the valley index [1, 2]. While progress has been made in controlling valley index of ensemble of charge carriers [3-5], valley control of individual charges, crucial for valleytronics, remains unexplored. Here, we provide unambiguous evidence for localized holes with net spin in optically active WSe 2 quantum dots (QDs) and control their spin-valley state with the helicity of the excitation laser under small magnetic field. We estimate a lower bound on the valley lifetime of a single charge in QD from recombination time to be ∼ nanoseconds. Remarkably, neutral QDs do not exhibit such a control, demonstrating the role of excess charge in prolonging the valley lifetime. Our work extends the field of 2D valleytronics to the level of single spin-valley, relevant for quantum information and sensing applications.Localized single spins in solid-state have been widely studied for quantum information technology, spintronics and quantum sensing [6,7], in addition to serving as a versatile playground for exploring many-body physics [8]. With the rise of semiconducting van der Waals (vdW) materials having direct band gap such as group VI-B transition metal dichalcogenides (TMDs), a arXiv:1810.01887v1 [cond-mat.mes-hall]

Identifying defect-related quantum emitters in monolayer WSe2

“…It is worth noting that these quantum emitters in our sample mainly result from defects other than strain effect since no intentional strain is introduced. And the emissions are assumed to be neutral excitons which usually appear without applied electric field [22,23]. The defects introduce various trapping energy levels [24,25,28,[49][50][51] within the electronic band gap of the WSe 2 , thus providing possibilities for various transitions.…”

“…Meanwhile, the properties of such a 2D host of quantum emitters have been intensely investigated, including 3D localized trions in heterostuctures [19], manipulation of fine structure splitting (FSS) [20] and photon-phonon interaction [21]. Furthermore, the optical initialization of a single spin-valley in charged WSe 2 quantum dots [22] and the ability to deterministically load either a single electron or single hole into a Van der Waals heterostructure quantum device via a Coulomb blockade [23] have been demonstrated, which enable a new class of quantum-confined spin system to store and process information. However, the origin of the 2D host of quantum emitters is still vague.…”

Near‐Field Energy Transfer between a Luminescent 2D Material and Color Centers in Diamond

“…Moreover, hybrid systems involving NV centers and 2D materials are potential candidates for spin transfer and spin valley physics. The latter has triggered intense research in TMDs and has potential for quantum information and sensing applications . The FRET process investigated here can potentially aid to determine the depth of shallow color centers in SCD given the FRET radius of the WSe 2 /NV pair is precisely known.…”

Dipolar interactions between localized interlayer excitons in van der Waals heterostructures

“…As the expected blueshift is U dd ∼ 1/r 3 ex where r ex is the interexcitonic distance, localized interlayer excitons are a good candidate to observe this effect. Localized excitons in monolayer WSe 2 have been shown to be single photon emitters with sharp linewidths [18,19] and can host a single charge and spin [20,21]. Very recently, localized interlayer excitons with sharp linewidths were reported in vdW heterostructures [22].…”