Transient THz conductivity of silicon with optical pumping above and below the second indirect transition

2016/08/05 by Novelli, Fabio, Davis, Jeffrey A
#FOS: Physical sciences #Optics (physics.optics) #Other Condensed Matter (cond-mat.other) #Strongly Correlated Electrons (cond-mat.str-el)

paper · doi:10.48550/arxiv.1608.01759

Abstract

Here we perform a series of time-resolved experiments where a 100 fs pump pulse is tuned between 528 nm and 555 nm, across the second indirect gap of intrinsic silicon at ~540 nm which involves electrons in a higher-lying conduction band with minimum at the L point. The photo-injected carriers, after inter- and intra-band relaxations are complete, are subsequently probed with high-field single-cycle terahertz radiation. When the energy of the pump pulses exceeds the second indirect gap, the probed terahertz absorption decreases by a factor 2.7±0.2. We suggest that this dramatic change could be due to the different phonon populations obtained when the carriers undergo the L to X inter-band scattering, instead of just cooling within the X-valley.

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