diff --git a/README.md b/README.md
index 9bd5eb8f3..2cc1f01d1 100644
--- a/README.md
+++ b/README.md
@@ -74,7 +74,7 @@ DeepXDE requires one of the following backend-specific dependencies to be instal
 
 - TensorFlow 1.x: [TensorFlow](https://www.tensorflow.org)>=2.7.0
 - TensorFlow 2.x: [TensorFlow](https://www.tensorflow.org)>=2.3.0, [TensorFlow Probability](https://www.tensorflow.org/probability)>=0.11.0
-- PyTorch: [PyTorch](https://pytorch.org)>=1.9.0
+- PyTorch: [PyTorch](https://pytorch.org)>=2.0.0
 - JAX: [JAX](https://jax.readthedocs.io), [Flax](https://flax.readthedocs.io), [Optax](https://optax.readthedocs.io)
 - PaddlePaddle: [PaddlePaddle](https://www.paddlepaddle.org.cn/en)>=2.6.0
 
diff --git a/deepxde/backend/pytorch/tensor.py b/deepxde/backend/pytorch/tensor.py
index 4d32d68f2..474293d9c 100644
--- a/deepxde/backend/pytorch/tensor.py
+++ b/deepxde/backend/pytorch/tensor.py
@@ -4,8 +4,8 @@
 import torch
 
 
-if Version(torch.__version__) < Version("1.9.0"):
-    raise RuntimeError("DeepXDE requires PyTorch>=1.9.0.")
+if Version(torch.__version__) < Version("2.0.0"):
+    raise RuntimeError("DeepXDE requires PyTorch>=2.0.0.")
 
 # To write device-agnostic (CPU or GPU) code, a common pattern is to first determine
 # torch.device and then use it for all the tensors.
diff --git a/deepxde/optimizers/__init__.py b/deepxde/optimizers/__init__.py
index 556761a86..b99904b2c 100644
--- a/deepxde/optimizers/__init__.py
+++ b/deepxde/optimizers/__init__.py
@@ -1,10 +1,22 @@
 import importlib
+import os
 import sys
 
 from .config import LBFGS_options, set_LBFGS_options, NNCG_options, set_NNCG_options
 from ..backend import backend_name
 
 
+# To get Sphinx documentation to build, we import all
+if os.environ.get("READTHEDOCS") == "True":
+    # The backend should be tensorflow/tensorflow.compat.v1 to ensure backend.tf is not
+    # None.
+    from . import jax
+    from . import paddle
+    from . import pytorch
+    from . import tensorflow
+    from . import tensorflow_compat_v1
+
+
 def _load_backend(mod_name):
     mod = importlib.import_module(".%s" % mod_name, __name__)
     thismod = sys.modules[__name__]
diff --git a/docs/index.rst b/docs/index.rst
index ab36ce6f1..306dcc79d 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -107,6 +107,7 @@ If you are looking for information on a specific function, class or method, this
   modules/deepxde.nn.tensorflow
   modules/deepxde.nn.tensorflow_compat_v1
   modules/deepxde.optimizers
+  modules/deepxde.optimizers.pytorch
   modules/deepxde.utils
 
 Indices and tables
diff --git a/docs/modules/deepxde.optimizers.pytorch.rst b/docs/modules/deepxde.optimizers.pytorch.rst
index a01e34f85..7451e2806 100644
--- a/docs/modules/deepxde.optimizers.pytorch.rst
+++ b/docs/modules/deepxde.optimizers.pytorch.rst
@@ -1,21 +1,11 @@
-deepxde.optimizers.pytorch package
-==================================
+deepxde.optimizers.pytorch
+==========================
 
-Submodules
-----------
+deepxde.optimizers.pytorch.nncg module
+--------------------------------------
 
-deepxde.optimizers.pytorch.optimizers module
---------------------------------------------
-
-.. automodule:: deepxde.optimizers.pytorch.optimizers
+.. automodule:: deepxde.optimizers.pytorch.nncg
    :members:
    :undoc-members:
    :show-inheritance:
 
-Module contents
----------------
-
-.. automodule:: deepxde.optimizers.pytorch
-   :members:
-   :undoc-members:
-   :show-inheritance:
diff --git a/docs/requirements.txt b/docs/requirements.txt
index 5d0c53fba..9f042ef45 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -9,7 +9,7 @@ tensorflow>=2.7.0
 # TensorFlow 2.x
 tensorflow-probability>=0.11.0
 # PyTorch
-torch<2.0.0  # build fails on RTD with torch 2.0.0
+torch
 # PaddlePaddle
 # https://paddle-wheel.bj.bcebos.com/develop/linux/linux-cpu-mkl-avx/paddlepaddle-0.0.0-cp38-cp38-linux_x86_64.whl
 paddlepaddle==2.6.0
diff --git a/docs/user/installation.rst b/docs/user/installation.rst
index 2dcf7eede..d7caa3ac2 100644
--- a/docs/user/installation.rst
+++ b/docs/user/installation.rst
@@ -14,7 +14,7 @@ DeepXDE requires one of the following backend-specific dependencies to be instal
 
     - For TensorFlow 2.16+ with Keras 3, refer to `the instruction <https://github.com/tensorflow/probability/releases/tag/v0.24.0>`_ for installing TensorFlow Probability.
 
-- PyTorch: `PyTorch <https://pytorch.org>`_>=1.9.0
+- PyTorch: `PyTorch <https://pytorch.org>`_>=2.0.0
 - JAX: `JAX <https://jax.readthedocs.io>`_, `Flax <https://flax.readthedocs.io>`_, `Optax <https://optax.readthedocs.io>`_
 - PaddlePaddle: `PaddlePaddle <https://www.paddlepaddle.org.cn/en>`_>=2.6.0
 
@@ -124,7 +124,7 @@ Export ``DDE_BACKEND`` as ``pytorch`` to specify PyTorch backend. In addition, i
 .. code:: python
 
     if torch.cuda.is_available():
-        torch.set_default_tensor_type(torch.cuda.FloatTensor)
+        torch.set_default_device("cuda")
 
 JAX backend
 ```````````