Absence of Magnetic-Field-Induced Effects in the Mid-infrared Transmission of La2-xSrxCuO4 Thin Films

We report magnetotransmission measurements on a series of La2-xSrxCuO4 thin films. The measurements were performed in magnetic fields of 18 T, on films with doping levels of x = 0, 0.01, 0.03, 0.045, 0.06, 0.08, and 0.10. In addition, an optimally doped film (x = 0.16) was studied in magnetic fields up to 33 T, both above and below its superconducting critical temperature Tc = 41 K. A combination of Gaussian and wavelet filtering was employed to improve the signal-to-noise ratio of the data. However, even after this procedure, we could not detect any field-induced changes of transmission in any of the studied samples. Our results therefore rule out a direct relation between intensity changes in mid-infrared charge excitations and a bosonic mode in the far infrared. We discuss these observations in the context of existing proposals regarding the nature of medium energy range excitations in the cuprates.