2018
DOI: 10.1038/s41467-018-03174-3
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Microsecond dark-exciton valley polarization memory in two-dimensional heterostructures

Abstract: Transition metal dichalcogenides have valley degree of freedom, which features optical selection rule and spin-valley locking, making them promising for valleytronics devices and quantum computation. For either application, a long valley polarization lifetime is crucial. Previous results showed that it is around picosecond in monolayer excitons, nanosecond for local excitons and tens of nanosecond for interlayer excitons. Here we show that the dark excitons in two-dimensional heterostructures provide a microse… Show more

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Cited by 130 publications
(150 citation statements)
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References 50 publications
(80 reference statements)
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“…The polarization degree of 0V-2 is much larger than that of 0V-1 and 0V-3. This observation further supports the presence of dark exciton 7,39 , because it has a long lifetime that suppresses valley depolarization 40,41 , as illustrated in Fig.4c and 4d. Due to long-range electron-hole exchange 40 , electrons in the K valley are scattered from the conduction band to the valence band, whereas electrons in the K' valley are scattered from the valence band to the conduction band.…”
Section: Introductionsupporting
confidence: 81%
See 1 more Smart Citation
“…The polarization degree of 0V-2 is much larger than that of 0V-1 and 0V-3. This observation further supports the presence of dark exciton 7,39 , because it has a long lifetime that suppresses valley depolarization 40,41 , as illustrated in Fig.4c and 4d. Due to long-range electron-hole exchange 40 , electrons in the K valley are scattered from the conduction band to the valence band, whereas electrons in the K' valley are scattered from the valence band to the conduction band.…”
Section: Introductionsupporting
confidence: 81%
“…This process can also be regarded as virtual recombination of an exciton in the K valley and generation of another exciton in the K' valley, or vice versa. The long-range electron-hole exchange typically takes a few picoseconds 41 , and the lifetime of the bright and dark IX is about several nanoseconds and microseconds 39 , respectively. Therefore, the valley depolarization is strong for bright IX (Fig.…”
Section: Introductionmentioning
confidence: 99%
“…The average linewidth of the observed peaks is about 100 μeV, which is comparable to the quantum emitters reported in monolayers of WSe2 (ref. [22][23][24][25] and hexagonal boron nitride 26 , and two orders of magnitude narrower than previous reports of interlayer exciton PL 10,[12][13][14][15][16][17]27,28 . Narrow PL peaks and power broadening were also observed in the 57° and 20° sample (Extended Data Fig.…”
Section: Main Textmentioning
confidence: 68%
“…Even after the recombination of exciton, which takes place after a few nanoseconds [19,20,22], one expects the spin-valley of single, localized hole to be preserved for a much longer time. In fact from the valley lifetime of free holes [14,16,17], we expect a single spin-valley lifetime on the order of microseconds, if not longer. On longer timescales, valley relaxation could be mediated by hyperfine interaction with nuclear spins, which is expected to be quite small in TMDs [24,36].…”
Section: Energy (Mev)mentioning
confidence: 95%
“…However, as recombination lifetimes of photogenerated excitations in TMDs is on the order of a few picoseconds, optically generated valley lifetime is limited to a similar timescale. On the other hand, valley polarization of free charge carriers, as opposed to photogenerated excitations, shows promising prospect with lifetimes on the order of microseconds reported for holes [14][15][16][17][18]. A natural question for quantum information science and quantum metrology applications is whether a single spin-valley can be optically addressed and manipulated.…”
mentioning
confidence: 99%