Light-Induced Melting of Competing Stripe Orders without Introducing Superconductivity in La2−xBaxCuO<mml:…

The ultrafast manipulation of quantum material has led to many novel and significant discoveries. Among them, the light-induced transient superconductivity in cuprates achieved by melting competing stripe orders represents a highly appealing accomplishment. However, recent investigations have shown that the notion of photoinduced superconductivity remains a topic of controversy, and its elucidation solely through <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mi>c</a:mi></a:mrow></a:math>-axis time-resolved terahertz spectroscopy remains an arduous task. Here, we measure the in-plane and out-of-plane transient terahertz responses simultaneously in the stripe-ordered nonsuperconducting <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mrow><c:msub><c:mrow><c:mi>La</c:mi></c:mrow><c:mrow><c:mn>2</c:mn><c:mo>−</c:mo><c:mi>x</c:mi></c:mrow></c:msub><c:mrow><c:msub><c:mrow><c:mi>Ba</c:mi></c:mrow><c:mrow><c:mi>x</c:mi></c:mrow></c:msub></c:mrow><c:mrow><c:msub><c:mrow><c:mi>CuO</c:mi></c:mrow><c:mrow><c:mn>4</c:mn></c:mrow></c:msub></c:mrow></c:mrow></c:math> after near-infrared excitations. We find that although a pump-induced reflectivity edge appears in the <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mrow><e:mi>c</e:mi></e:mrow></e:math>-axis reflectance spectrum, the reflectivity along the <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mrow><g:msub><g:mrow><g:mi>CuO</g:mi></g:mrow><g:mrow><g:mn>2</g:mn></g:mrow></g:msub></g:mrow></g:math> planes decreases simultaneously, indicating an enhancement in the scattering rate of quasiparticles. This in-plane transient response is clearly distinct from the features associated with superconducting condensation. Therefore, we conclude the out-of-plane transient responses cannot be explained by an equivalent of Josephson tunneling. Notably, those pump-induced terahertz responses remain consistent even when we vary the near-infrared optical pump wavelengths and hole concentrations. Our results provide critical evidence that transient three-dimensional superconductivity cannot be induced by melting the competing stripe orders with pump pulses whose photon energy is much higher than the superconducting gap of cuprates. Published by the American Physical Society 2024