I am a 4th-year PhD candidate in School of Intelligence Science and Technology at Peking University, working with Prof. Yan Zhang. I obtained my bachelor’s degree from the School of Computer Science and Engineering, UESTC in June 2021, under the supervision of Prof. Kai Zheng. I’ve also spent time at Tongyi Lab, Baidu Reserch, MSRA, DAMO Academy and Huawei.

I am expected to complete my Ph.D. in June 2026 and will be actively seeking opportunities in both industry and academia. If you are interested, please feel free to reach out.

🔥 News

  • 2025.05:  🎉🎉 I am honored to receive the Presidential Scholarship (the highest honor for PhD students at PKU)!
  • 2025.05:  🎉🎉 My paper entitled “Enhancing Retrieval-Augmented Generation via Evidence Tree Search” was accepted by ACL 2025!
  • 2025.05:  🎉🎉 My paper entitled “Unveil: Unified Visual-Textual Integration and Distillation for Multi-modal Document Retrieval” was accepted by ACL 2025!
  • 2025.05:  🎉🎉 My paper entitled “ZeroSearch: Incentivize the Search Capability of LLMs without Searching” is on Arxiv!
  • 2025.04:  🎉🎉 I am honored to receive the Academic Star Award (Top-5 students in School of Intelligence Science and Technology)!
  • 2024.09:  🎉🎉 My paper entitled “Towards Verifiable Text Generation with Evolving Memory and Self-Reflection” was accepted by EMNLP 2024!
  • 2024.09:  🎉🎉 My paper entitled “Retrieved In-Context Principles from Previous Mistakes” was accepted by EMNLP 2024!
  • 2024.09:  🎉🎉 My paper entitled “AdaSwitch: Adaptive Switching between Small and Large Agents for Effective Cloud-Local Collaborative Learning” was accepted by EMNLP 2024!
  • 2023.10:  🎉🎉 My paper entitled “LEAD: Liberal Feature-based Distillation for Dense Retrieval” was accepted by WSDM 2024!
  • 2023.10:  🎉🎉 My paper entitled “Allies: Prompting Large Language Model with Beam Search” was accepted by EMNLP 2023!
  • 2023.08:  🎉🎉 Awarded as Stars of Tomorrow during an internship at Microsoft!
  • 2023.05:  🎉🎉 My paper entitled “History Semantic Graph Enhanced Conversational KBQA with Temporal Information Modeling” was accepted by ACL 2023!

🌟 Highlight

Under Review
sym

ZeroSearch: Incentivize the Search Capability of LLMs without Searching

Hao Sun, Z. Qiao, J. Guo, X. Fan, Y. Hou, Y. Jiang, P. Xie, F. Huang, Y. Zhang

Under Review

Homepage | Paper | Code | Models 900+ stars!

We propose a novel reinforcement learning framework that incentivizes the search capability of LLMs without interacting with real search engines.

Under Review
sym

HRM: Enhancing Agentic Retrieval Augmented Generation With Hierarchical Reward Modeling

Hao Sun, Z. Qiao, B. Wang, G. Chen, Y. Hou, Y. Jiang, P. Xie, F. Huang, Y. Zhang

Under Review

Paper

We propose a novel Agentic RAG framework that independently optimizes planning reasoning and search grounding with dual value models.

📝 Publications

ACL 2025
sym

Enhancing Retrieval-Augmented Generation via Evidence Tree Search

Hao Sun, H Cai, Y. Li, X. Fan, X. Wei, S. Wang, Y. Zhang, D. Yin

The Annual Meeting of the Association for Computational Linguistics (ACL), 2025

Paper

We propose ETS, a tree-based framework that enhances LLMs’ evidence-grounding through a tree expansion process.

ACL 2025
sym

Unveil: Unified Visual-Textual Integration and Distillation for Multi-modal Document Retrieval

Hao Sun, Y. Hou, J. Guo, B. Wang, C. Yang, J. Ni, Y. Zhang

The Annual Meeting of the Association for Computational Linguistics (ACL), 2025

Paper

Transfer the semantic understanding capabilities from the visual-textual embedding model to a purely visual model.

ACL 2023
sym

History Semantic Graph Enhanced Conversational KBQA with Temporal Information Modeling

Hao Sun, Y.g Li, L. Deng, B. Li, B. Hui, B. Li, Y. Lan, Y. Zhang, Y. Li

The Annual Meeting of the Association for Computational Linguistics (ACL), 2023

Paper

Modeling history conversation information with History Semantic Graph.

EMNLP 2024
sym

Towards Verifiable Text Generation with Evolving Memory and Self-Reflection

Hao Sun, H. Cai, B. Wang, Y. Hou, X. Wei, S. Wang, Y. Zhang, D. Yin

The Conference on Empirical Methods in Natural Language Processing (EMNLP), 2024

Paper

Improving citation generation with a two-tier verifier and active retrieval mechanism.

EMNLP 2024
sym

Retrieved In-Context Principles from Previous Mistakes

Hao Sun, Y. Jiang, B. Wang, Y. Hou, Y. Zhang, P. Xie, F. Huang

The Conference on Empirical Methods in Natural Language Processing (EMNLP), 2024

Paper

Enabling LLMs to learn from mistakes by providing question-level and task-level principles.

EMNLP 2024
sym

AdaSwitch: Adaptive Switching between Small and Large Agents for Effective Cloud-Local Collaborative Learning

Hao Sun, J. Wu, H. Cai, X. Wei, Y. Feng, B. Wang, S. Wang, Y. Zhang, D. Yin

The Conference on Empirical Methods in Natural Language Processing (EMNLP), 2024

Paper

Enabling adaptive switching between local agent and cloud agent through collaborative learning.

EMNLP 2023
sym

Allies: Prompting Large Language Model with Beam Search

Hao Sun, X. Liu, Y. Gong, Y. Zhang, N. Duan

The Conference on Empirical Methods in Natural Language Processing (EMNLP), 2023, Findings

Paper | Code

Improving the knowledge scope and robustness of LLMs with Beam Search.

WSDM 2024
sym

LEAD: Liberal Feature-based Distillation for Dense Retrieval

Hao Sun, X. Liu, Y. Gong, A. Dong, J. Lu, Y. Zhang, L. Yang, R. Majumder, N. Duan

The ACM International Conference on Web Search and Data Mining (WSDM), 2024, Oral

Paper | Code

Distilling the intermediate features from teacher to student without the constraints on model architecture or tokenizers.

CIKM 2021
sym

PeriodicMove: Shift-aware Human Mobility Recovery with Graph Neural Network

Hao Sun, C. Y.g, L. Deng, F. Zhou, F. Huang, K. Zheng

The ACM International Conference on Information and Knowledge Management (CIKM), 2021

Paper | Code

Capturing multi-level periodicity and shifting periodicity of human mobility using attention mechanism.

SDM 2022
sym

ConLearn: Contextual-knowledge-aware Concept Prerequisite Relation Learning with Graph Neural Network

Hao Sun, Y. Li, Y. Zhang

The SIAM International Conference on Data Mining (SDM), 2022

Paper | Code

Capturing complex transition patterns between concepts through Graph Neural Network.

DASFAA 2021
sym

Personalized Dynamic Knowledge-Aware Recommendation with Hybrid Explanations

Hao Sun, Z. Wu, Y. Cui, L. Deng, Y. Zhao, K. Zheng

The International Conference on Database Systems for Advanced Applications (DASFAA), 2021

Paper

Providing personalized and hybrid explanations for the recommendations.

NeurIPS 2024
sym

Cross-model Control: Improving Multiple Large Language Models in One-time Training

J. Wu, Hao Sun, H Cai, L Su, S Wang, D Yin, X Li, M Gao

The Annual Conference on Neural Information Processing Systems (NeurIPS), 2024

Paper | Code

Improves multiple LLMs in one-time training with a portable tiny language model.

NeurIPS 2022
sym

A Neural Corpus Indexer for Document Retrieval

Y. Wang, Y. Hou, H. Wang, Z. Miao, S. Wu, Hao Sun, Q. Chen, Y. Xia, C. Chi, G. Zhao, Z. Liu, X. Xie, H. Allen Sun, W. Deng, Q. Zhang, M. Yang

The Annual Conference on Neural Information Processing Systems (NeurIPS), 2024

Paper | Code 🏆 Outstanding Paper Award!

Propose an end-to-end differentiable document retrieval model that can significantly outperform both inverted index and dense retrieval solutions.

ACL 2025
sym

Unraveling the Mechanics of Learning-Based Demonstration Selection for In-Context Learning

H. Liu, W. Wang, Hao Sun, C. TIAN, C. Kong, X. Dong, H. Li

The Annual Meeting of the Association for Computational Linguistics (ACL), 2025

Paper

Analyze the working mechanism of learning-based demonstration selection methods.

NAACL 2025
sym

PA-RAG: RAG Alignment via Multi-Perspective Preference Optimization

J. Wu, H. Cai, L. Yan, Hao Sun, X. Li, S. Wang, D. Yin, M. Gao

The Annual Conference of the Nations of the Americas Chapter of the Association for Computational Linguistics (NAACL), 2025

Paper | Code

Optimizing the RAG generator to align with RAG requirements comprehensively.

TOIS 2021
sym

Sequential-Knowledge-Aware Next POI Recommendation: A Meta-Learning Approach

Y. Cui, Hao Sun, Y. Zhao, H. Yin, K. Zheng

The ACM Transactions on Information Systems (TOIS), 2021

Paper

Utilize sequential, spatiotemporal, and social knowledge to recommend the next POI for a location-based social network user.

TIFS 2024
sym

Robust domain misinformation detection via multi-modal feature alignment

H. Liu, W. Wang, Hao Sun, A. Rocha, H. Li

IEEE Transactions on Information Forensics and Security (TIFS), 2024

Paper

Propose a novel robust domain and cross-modal approach (RDCM) for multi-modal misinformation detection.

WSDM 2023
sym

S2TUL: A Semi-Supervised Framework for Trajectory-User Linking

L. Deng, Hao Sun, Y. Zhao, S. Liu, K. Zheng

The ACM International Conference on Web Search and Data Mining (WSDM), 2023

Paper

Capture fine-grained intra-trajectory information by passing the trajectories into the sequential neural networks.

CIKM 2022
sym

Efficient Trajectory Similarity Computation with Contrastive Learning

L. Deng, Y. Zhao, Z. Fu, Hao Sun, S. Liu, K. Zheng

The ACM International Conference on Information and Knowledge Management (CIKM), 2022

Paper

Employ a contrastive learning mechanism to learn the representations of trajectories, which are then used to calculate the dissimilarity between them.

TIST 2022
sym

Efficient and Effective Similar Subtrajectory Search: A Spatial-aware Comprehension Approach

L. Deng, Hao Sun, R. Sun, Y. Zhao, H. Su

The ACM Transactions on Intelligent Systems and Technology (TIST), 2022

Paper

Propose a Similar Subtrajectory Search with a Graph Neural Networks framework.

CIKM 2022
sym

Fusing Local and Global Mobility Patterns for Trajectory Recovery

L. Deng, Y. Zhao, Hao Sun, C. Yang, J. Xie, K. Zheng

The ACM International Conference on Information and Knowledge Management (CIKM), 2022

Paper

Propose a neural attention model based on graph convolutional networks to enhance the accuracy of trajectory recovery.

ICME 2024
sym

Boosting Disfluency Detection with Large Language Model as Disfluency Generator

Z. Cheng, J. Guo, Hao Sun, Y. Zhang

The IEEE International Conference on Multimedia & Expo (ICME), 2024

Paper

Propose a framework that addresses data sparsity issues by generating disfluent data using LLM as augmentation data.

📒 Preprint

Under Review
sym

SimCNS: Simple Curriculum Negative Sampling for Multi-Source Dense Retrieval

Hao Sun, X. Liu, Y. Gong, A. Dong, G. Shi, Y. Zhang, L. Yang, N. Duan

Under Review

Paper

Improving multi-source dense retrieval with Curriculum Negative Sampling.

🎖 Honors and Awards

  • 2025.05 Presidential Scholarship, Peking University.
  • 2025.04 Academic Star Award, Peking University.
  • 2024.06 First Prize of Challenge Cup Competition, Peking University.
  • 2023.09 Merit Student, Peking University.
  • 2023.09 Schlumberger Scholarship, Peking University.
  • 2023.08 Stars of Tomorrow Award, Microsoft.
  • 2023.06 First Prize of Challenge Cup Competition, Peking University.
  • 2022.12 Outstanding Paper Award, NeurIPS 2022.
  • 2021.06 Outstanding Graduation Thesis for Undergraduates, UESTC.
  • 2021.06 Outstanding Graduate, UESTC.
  • 2019.12 National Scholarship.
  • 2018.09 National Scholarship.

📖 Educations

  • 2021.09 - Present, Ph.D. Candidate, Peking University.
  • 2017.09 - 2021.06, Undergraduate, University of Electronic Science And Technology of China.

📚 Academic Services

  • Program Committee / Reviewer: ARR 2022-25, NeurIPS 2024-2025, ICLR 2024-2025, ICML 2024-2025
  • Secondary Reviewer: AAAI 2022, CIKM 2021-22, ICDM 2021-23, COLING 2022-23, DASFAA 2022-23

👩🏻‍🏫 Teaching

  • Teaching Assistant, Computer Networks and Web Technologies, Peking University, Fall 2023

💻 Internships