新型半导体纳米结构中负质量电子的影响诸平A red laser beam impinges on the atomically thin crystal WSe2, which converts the red light of the laser into a blue glow. Credit: Felix Hofmann据德国雷根斯堡大学（University of Regensburg）2021年9月17日提供的消息，由雷根斯堡大学实验与应用物理研究所（Institute of Experimental and Applied Physics at the University of Regensburg）的林凯强博士（Dr. Kai-Qiang Lin音译）和约翰·勒普顿（John Lupton）教授领导的一个大型国际研究合作，已经能够测量具有负质量的电子（electrons with negative mass）在新型半导体纳米结构（novel semiconductor nanostructures）中的影响（Effect of electrons with negative mass in novel semiconductor nanostructures）。
Illustration of negative mass using a golf ball in a glass of water. The fall of a conventional golf ball is slowed down by the water. A golf ball of negative mass, on the other hand, would be accelerated by the frictional resistance. Credit: Felix Hofmann插图是一个负质量的高尔夫球在一杯水中的下沉情况，传统高尔夫球的下落会被水减慢。
Kai-Qiang Lin, Chin Shen Ong, Sebastian Bange, Paulo E. Faria Junior, Bo Peng, Jonas D. Ziegler, Jonas Zipfel, Christian Bäuml, Nicola Paradiso, Kenji Watanabe, Takashi Taniguchi, Christoph Strunk, Bartomeu Monserrat, Jaroslav Fabian, Alexey Chernikov, Diana Y. Qiu, Steven G. Louie, John M. Lupton. Narrow-band high-lying excitons with negative-mass electrons in monolayer WSe2. Nature Communications, 2021, Volume 12, Article number: 5500. DOI: 10.1038/s41467-021-25499-2. Published: 17 September 2021AbstractMonolayer transition-metal dichalcogenides (TMDCs) show a wealth of exciton physics. Here, we report the existence of a new excitonic species, the high-lying exciton (HX), in single-layer WSe2 with an energy of ~3.4 eV, almost twice the band-edge A-exciton energy, with a linewidth as narrow as 5.8 meV. The HX is populated through momentum-selective optical excitation in the K-valleys and is identified in upconverted photoluminescence (UPL) in the UV spectral region. Strong electron-phonon coupling results in a cascaded phonon progression with equidistant peaks in the luminescence spectrum, resolvable to ninth order. Ab initio GW-BSE calculations with full electron-hole correlations explain HX formation and unmask the admixture of upper conduction-band states to this complex many-body excitation. These calculations suggest that the HX is comprised of electrons of negative mass. The coincidence of such high-lying excitonic species at around twice the energy of band-edge excitons rationalizes the excitonic quantum-interference phenomenon recently discovered in optical second-harmonic generation (SHG) and explains the efficient Auger-like annihilation of band-edge excitons. ... 阅读全文
Illustration of negative mass using a golf ball in a glass of water. The fall of a conventional golf ball is slowed down by the water. A golf ball of negative mass, on the other hand, would be accelerated by the frictional resistance. Credit: Felix Hofmann插图是一个负质量的高尔夫球在一杯水中的下沉情况，传统高尔夫球的下落会被水减慢。
Kai-Qiang Lin, Chin Shen Ong, Sebastian Bange, Paulo E. Faria Junior, Bo Peng, Jonas D. Ziegler, Jonas Zipfel, Christian Bäuml, Nicola Paradiso, Kenji Watanabe, Takashi Taniguchi, Christoph Strunk, Bartomeu Monserrat, Jaroslav Fabian, Alexey Chernikov, Diana Y. Qiu, Steven G. Louie, John M. Lupton. Narrow-band high-lying excitons with negative-mass electrons in monolayer WSe2. Nature Communications, 2021, Volume 12, Article number: 5500. DOI: 10.1038/s41467-021-25499-2. Published: 17 September 2021AbstractMonolayer transition-metal dichalcogenides (TMDCs) show a wealth of exciton physics. Here, we report the existence of a new excitonic species, the high-lying exciton (HX), in single-layer WSe2 with an energy of ~3.4 eV, almost twice the band-edge A-exciton energy, with a linewidth as narrow as 5.8 meV. The HX is populated through momentum-selective optical excitation in the K-valleys and is identified in upconverted photoluminescence (UPL) in the UV spectral region. Strong electron-phonon coupling results in a cascaded phonon progression with equidistant peaks in the luminescence spectrum, resolvable to ninth order. Ab initio GW-BSE calculations with full electron-hole correlations explain HX formation and unmask the admixture of upper conduction-band states to this complex many-body excitation. These calculations suggest that the HX is comprised of electrons of negative mass. The coincidence of such high-lying excitonic species at around twice the energy of band-edge excitons rationalizes the excitonic quantum-interference phenomenon recently discovered in optical second-harmonic generation (SHG) and explains the efficient Auger-like annihilation of band-edge excitons. ... 阅读全文