Actually, there is.
The A-bomb was a very efficient killer. But it was no more lethal than the massive firebombing of 68 cities that Japan had previously endured. 120K dead in Tokyo, more than Hiroshima and Nagasaki combined. Yet Japan soldiered on. Is it reasonable to believe that they capitulated just because the mode of destruction had changed?
If we believe that Japan was ready to sacrifice a million-plus citizens to defend the homeland, it doesn't seem likely that the A-bomb would break their spirit. Especially since conventional bombing didn't. So then, why did they surrender?
Linked article suggests that it wasn't the A-bomb that ended the war - it was Russia's concurrent declaration of war and invasion of Japan's occupied territory.
Here is the theory. By 1945 (actually, well before then) Japan knew that they couldn't "win" the war. All they could do was inflict enough American casualties so that we would say F-it, negotiate a peace agreement favorable to Japan, and go home.
But once Stalin was involved it was game over. No amount of Russian deaths would deter him. Far better for Japan to surrender to the US while they still could. Which is what they did.
https://foreignpolicy.com/2013/05/30/the-bomb-didnt-beat-japan-stalin-did/