Mining temporal motifs in temporal graphs is essential for many critical applications. Although several solutions have been proposed to handle temporal motif mining, they still suffer from substantial inefficiencies due to significant \textit{redundant graph traversals} and \textit{fragmented memory access}, both caused by irregular search tree expansions across different motif matching tasks. In this work, we observe that data accesses issued by these tasks exhibit strong \textit{spatial similarity} and \textit{temporal monotonicity}. Based on these observations, this paper proposes an efficient data-centric temporal motif mining system \textsc{DTMiner}, which introduces a novel \textit{Load-Explore-Synchronize} (LES) execution model to efficiently regularize data accesses to the common temporal graph data among different tasks. Specifically, \textsc{DTMiner} enables the temporal graph chunks to be sequentially loaded into the cache in temporal order and then triggers all relevant tasks to explore only these loaded data for search tree expansions in a fine-grained synchronization mechanism. In this way, different tasks can share the graph traversal corresponding to the same chunks, while fragmented memory accesses are restricted to the graph data residing in the cache, significantly reducing data access overhead. Experimental results demonstrate that \textsc{DTMiner} achieves 1.14$\times$-11.98$\times$ performance improvement in comparison with the state-of-the-art temporal motif mining solutions.