Resonant optical Stark effect in monolayer WS2

Abstract

Breaking the valley degeneracy in monolayer transition metal dichalcogenides through the valley-selective optical Stark effect (OSE) can be exploited for classical and quantum valleytronic operations such as coherent manipulation of valley superposition states. The strong light-matter interactions responsible for the OSE have historically been described by a two-level dressed-atom model, which assumes noninteracting particles. Here we experimentally show that this model, which works well in semiconductors far from resonance, does not apply for excitation near the exciton resonance in monolayer WS2. Instead, we show that an excitonic model of the OSE, which includes many-body Coulomb interactions, is required. We confirm the prediction from this theory that many-body effects between virtual excitons produce a dominant blue-shift for photoexcitation detuned from resonance by less than the exciton binding energy. As such, we suggest that our findings are general to low-dimensional semiconductors that support bound excitons and other many-body Coulomb interactions.

Valley-selective optical Stark effect of exciton-polaritons in a monolayer semiconductor

“…The effect remains valley-selective over a wide range of cavity-exciton detunings, paving the way towards coherent control of valley in regimes that accentuate the light-like properties of polaritons. In bare TMD excitons, circularly-polarized pump fields tuned above 34 , below 8,35 , and on-resonance 9 with various exciton transitions have revealed valley-dependent couplings between optical fields and different exciton species. Similarly, the valleysensitivity of the polaritonic Stark shift established in this work should extend to alternative pumping regimes, creating rich opportunities to explore additional valley-dependent couplings in 2D polaritons.…”

Поглощение Мощного Света Свободными Электронами В Кристаллах: Внутризонные Электрон-Фононные Осцилляции Раби

“…В этом случае проявляется резонанс Фано [49] в электрон-фотонной системе. В работе [39] исследовался ОЭШ под действием длинноволнового излучения CO 2 -лазера при резонансе на переходах между экситонными состояниями 1s и 2p в Cu 2 O. В работе [40] по ОЭШ в квантовых точках и большинстве других работ по ОЭШ (см., например, [40][41][42]50,[55][56][57][58][59][60]) использовалось лазерное излучение с частотой, несколько меньшей ширины запрещенной зоны. В работах [43,44] исследовались сдвиги экситонных уровней с учетом многочастичных эффектов за счет заполнения зон при двухфотонных межзонных переходах.…”

“…В работах [57,59] изучался ОЭШ в экситонно-биэкситонных системах. Поляризационно-зависимый ОЭШ стал предметом изучения в [57][58][59]. В работах [45,46,52,53] рассматривался ОЭШ в условиях двойного однофотоннооднофотонного [46], двухфотонно-однофотонного [45] и многофотонно-двухфотонного резонанса на смежных межзонных переходах.…”

Molecular Radiative Energy Shifts under Strong Oscillating Fields

“…[1][2][3] While the maximum coupling strength is achieved in the resonant limit, the non-resonant excitation results in the distinct optical Stark effect (OSE) that is fundamental to coherent light-matter interactions. [4][5][6][7][8][9][10] As a nonlinear effect, OSE is manifested as the transient perturbation to energy levels under non-resonant laser pumping. Harnessing the unique properties of OSE enables coherent manipulation of hybrid states by ultrafast all-optical tuning, as has been demonstrated in monolayer transition metal dichalcogenides, [7,9,10] perovskite thin films, [8] and quantum dots [4,5] among others.…”

“…[4][5][6][7][8][9][10] As a nonlinear effect, OSE is manifested as the transient perturbation to energy levels under non-resonant laser pumping. Harnessing the unique properties of OSE enables coherent manipulation of hybrid states by ultrafast all-optical tuning, as has been demonstrated in monolayer transition metal dichalcogenides, [7,9,10] perovskite thin films, [8] and quantum dots [4,5] among others. However, the occurrence of OSE is strongly dependent on the laser pumping.…”